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    @sap/approuter

    11.5.0 • Public • Published

    @sap/approuter

    Overview

    When a business application consists of several different apps (microservices), the application router is used to provide a single entry point to that business application. It has the responsibility to:

    • Dispatch requests to backend microservices (reverse proxy)
    • Authenticate users
    • Serve static content

    Application router overview diagram

    Let's think of the different apps (microservices) as destinations to which the incoming request will be forwarded. The rules that determine which request should be forwarded to which destination are called routes. For every destination there can be more than one route. You may read more on the concept of routes later in this document. If the backend microservices require authentication, the application router can be configured to authenticate the users and propagate the user information. Again by using routes, the application router can serve static content.

    The application router is designed to work in XS Advanced - Cloud Foundry and XS OnPremise Runtime.

    A calling component accesses a target service by means of the application router only if there is no JWT token available, for example, if a user invokes the application from a Web browser. If a JWT token is already available, for example, because the user has already been authenticated, or the calling component uses a JWT token for its own OAuth client, the calling component calls the target service directly; it does not need to use the application router.

    Note that the application router does not hide the backend microservices in any way. They are still directly accessible bypassing the application router. So the backend microservices must protect all their endpoints by validating the JWT token and implementing proper scope checks. Network isolation is not provided currently by the platform.

    Deploying a business application with microservices

    For example we can have a business application that has the following structure:

    +-- manifest.yml
    +-- manifest-op.yml
    |  +-- microservice-1
    |  | +-- ...
    |  | +-- ...
    |  +-- microservice-2
    |  | +-- ...
    |  | +-- ...
    |  +-- web
    |  | +-- ...
    |  | +-- ...
    

    The manifest.yml file is used to deploy the business application on Cloud Foundry and the manifest-op.yml - on the XS OnPremise Runtime. These files should describe all the microservices for that business application.

    Folders are used to isolate the different microservices. Let's assume that the application router is the microservice in the web folder (every business application has its own application router). Here is how we can include the application router:

    • Manually create the node_modules folder in the web folder.
    • Copy and paste the folder that contains the self-contained application router into node_modules. In this example the name of that folder is @sap/approuter, see the start script in the package.json below.
    • Check the version of the application router you just copied.
    • Create a package.json file in web with content similar to the following and replace the version's value with the version of your application router:
    {
        "name": "hello-world-approuter",
        "dependencies": {
           "@sap/approuter": "2.6.1"
        },
        "scripts": {
            "start": "node node_modules/@sap/approuter/approuter.js"
        }
    }

    In order to use the application router you don't have to write any JavaScript code. Only some configurations have to be provided in the web folder. Here is a complete example:

    +-- web
    | +-- package.json
    | +-- xs-app.json
    | +-- resources
    | | +-- hello-world.html
    | | +-- my-page.html
    | +-- node_modules
    | |   +-- ...
    | +-- default-env.json
    | +-- default-services.json
    

    The web folder contains the package.json, node_modules, some configuration files used by the application router, and static resources to be served. You can read more about the configurations later in this document.

    By default, the application router runs on port 5000 (if started locally) or it takes the port from the PORT environment variable.

    Working directory

    The working directory contains configuration files that the application router needs and static resources that can be served at runtime. In the previous example, the web folder is the working directory. By default the current directory is the working directory. It is possible to configure it during start up of the application router with the following command line argument:

    node approuter.js -w <working-dir>

    Application router will abort if the working directory does not contain xs-app.json file.

    Configurations

    The application router makes use of the following configurations:

    • Main configuration - this is the xs-app.json file. This file is mandatory and contains the main configurations of the application router.

    • UAA configuration - the application router reads this configuration either from the VCAP_SERVICES environment variable (when deployed on Cloud Foundry or XS Advanced OnPremise Runtime) or from the default-services.json file (when running locally). Refer to the documentation of the @sap/xsenv package for more details.

    • Configurations from the environment - these configurations are either read from the application router's environment (when deployed on Cloud Foundry or XS Advanced OnPremise Runtime) or from the default-env.json file (when running locally). Refer to the documentation of the @sap/xsenv package for more details. The environment variables that the application router takes into account are:

    Configuration Environment variable Description
    UAA service name UAA_SERVICE_NAME Contains the name of the UAA service to be used.
    Destinations destinations Provides information about the available destinations.
    Additional headers httpHeaders Provides headers that the application router will return to the client in its responses.
    Additional cookies COOKIES Provides cookies that the application router will return to the client in its responses. Currently only SameSite cookie is supported.
    Plugins plugins A plugin is just like a route except that you can't configure some inner properties.
    Session timeout SESSION_TIMEOUT Positive integer representing the session timeout in minutes. The default timeout is 15 minutes.
    X-Frame-Options SEND_XFRAMEOPTIONS, httpHeaders Configuration for the X-Frame-Options header value.
    Allowlist service CJ_PROTECT_WHITELIST Configuration for the allowlist that is preventing clickjack attacks.
    Web Sockets origins allowlist WS_ALLOWED_ORIGINS An allowlist configuration that is used for verifying the Origin header of the initial upgrade request when establishing a web socket connection.
    JWT Token refresh JWT_REFRESH The time in minutes before a JWT token expires and the application router should trigger a token refresh routine.
    Incoming connection timeout INCOMING_CONNECTION_TIMEOUT Maximum time in milliseconds for a client connection. After that time the connection is closed. If set to 0, the timeout is disabled. Default: 120000 (2 min)
    Tenant host pattern TENANT_HOST_PATTERN String containing a regular expression with a capturing group. The request host is matched against this regular expression. The value of the first capturing group is used as tenant id.
    Destination host pattern DESTINATION_HOST_PATTERN String containing a regular expression with a capturing group. The request host is matched against this regular expression. The value of the capturing group is used as destination name.
    Compression COMPRESSION Configuration regarding compressing resources before responding to the client.
    Secure flag of session cookie SECURE_SESSION_COOKIE Can be set to true or false. By default, the Secure flag of the session cookie is set depending on the environment the application router runs in. For example, when application router is behind a router (Cloud Foundry's router or SAP Web Dispatcher) that is configured to serve HTTPS traffic, then this flag will be present. During local development the flag is not set. This environment variable can be used to enforce setting or omitting the Secure flag. Note: If the Secure flag is enforced, the application router will reject requests sent over unencrypted connection (http).
    Trusted CA certificates XS_CACERT_PATH List of files paths with trusted CA certificates used for outbound https connections (UAA, destinations, etc.). File paths are separated by path.delimiter. If this is omitted, several well known "root" CAs (like VeriSign) will be used. This variable is set automatically by XSA On-premise runtime.
    Reject untrusted certificates NODE_TLS_REJECT_UNAUTHORIZED By default an outbound https connection is terminated if the remote end does not provide a trusted certificate. This check can be disabled by setting NODE_TLS_REJECT_UNAUTHORIZED to 0. This is a built-in feature of Node.js. Note: Do not use this in production as it compromises security!
    External reverse proxy flag EXTERNAL_REVERSE_PROXY Boolean value that indicates the use of application router behind an external reverse proxy (outside of Cloud Foundry domain)
    Skip client credentials tokens load on start SKIP_CLIENT_CREDENTIALS_TOKENS_LOAD Boolean value that indicates that no client credentials tokens should be created during the application router start phase
    Cross-Origin Resource Sharing CORS Configuration regarding CORS enablement.
    Preserve URL fragment PRESERVE_FRAGMENT When set to true or not set, fragment part of the URL provided during first request of not logged-in user to protected route will be preserved, and after login flow user is redirected to original URL including fragment part. However, this may break programmatic access to Approuter (e.g. e2e tests), since it introduces change in login flow, which is incompatible with Approuter version 4.0.1 and earlier. Setting value to false makes login flow backward compatible, however will not take fragment part of the URL into account.
    Direct Routing URI Patterns DIRECT_ROUTING_URI_PATTERNS Configuration for direct routing URI patterns.
    NodeJS Minimal Logging Level CF_NODEJS_LOGGING_LEVEL Configuration for NodeJS minimal logging level.
    Dynamic Identity Provider DYNAMIC_IDENTITY_PROVIDER Configuration for dynamic identity provider.
    Backend Cookies Secret BACKEND_COOKIES_SECRET Secret that is used to encrypt backend session cookies in service to Application Router flow. Should be set in case multiple instances of Application Router are used. By default a random sequence of characters is used.
    Service to Application Router SERVICE_2_APPROUTER If true, when the SAP Passport header is received from the application router, it will be transferred without modification to the backend application.
    Client certificate header name CLIENT_CERTIFICATE_HEADER_NAME When set application router will use this header name to get the client certificate from the request header in subscription callback. If not provided the default header name x-forwarded-client-cert is used.
    Server Keep Alive SERVER_KEEP_ALIVE server keep alive timeout (positive integer in milliseconds).
    Minimum Token Validity MINIMUM_TOKEN_VALIDITY positive integer in seconds. When set, approuter will check that the token returned from the authorization service has an expiration time higher than the minimum token validity value.
    State Parameter Secret STATE_PARAMETER_SECRET enables the use of state parameters to prevent CRFS attacks. If this environment variable is set, the application router creates a state parameter for each initial authorization request. By validating that the authentication server returns the same state parameter in its response, the application server can verify that the response did not originate from a third party. Note: this feature is only available in Cloud Foundry runtime

    Note: all those environment variables are optional.

    Destinations

    The destinations configuration can be provided by the destinations environment variable or by destination service. There has to be a destination for every single app (microservice) that is a part of the business application.

    Environment destinations

    The destinations configuration is an array of objects. Here are the properties that a destination can have:

    Property Type Optional Description
    name String A unique alphanumeric identifier of the destination.
    url String URL of the app (microservice).
    proxyHost String x The host of the proxy server used in case the request should go through a proxy to reach the destination.
    proxyPort String x The port of the proxy server used in case the request should go through a proxy to reach the destination.
    forwardAuthToken Boolean x If true, the OAuth token is sent to the destination. The default value is false. This token contains user identity, scopes and other attributes. It is signed by the UAA or IAS service, so it can be used for user authentication and authorization with backend services.
    strictSSL Boolean x Configures whether the application router should reject untrusted certificates. The default value is true.
    Note: Do not use this in production as it compromises security!
    timeout Number x Positive integer representing the maximum wait time for a response (in milliseconds) from the destination. Default is 30000ms.
    setXForwardedHeaders Boolean x If true , the application router adds X-Forwarded-(Host, Path, Proto) headers to the backend request.Default value is true.
    proxyType String x Configures whether the destination is used to access applications in on-premise networks or on public Internet. Possible value: OnPremise. if the property is not provided, it is assumed that it is a public Internet access.
    Note: if OnPremise value is set, binding to SAP Cloud Platform connectivity service is required, and forwardAuthToken property should not be set.

    Note: The timeout specified will also apply to the destination's logout path or service's logout path (if you have set one).
    Note: proxyHost and proxyPort are optional, but if one of them is defined, then the other one becomes mandatory.

    Sample content of the destinations environment variable:

    [
      {
        "name" : "ui5",
        "url" : "https://ui5.sap.com",
        "proxyHost" : "proxy",
        "proxyPort" : "8080",
        "forwardAuthToken" : false,
        "timeout" : 1200
      }
    ]

    It is also possible to include the destinations in the manifest.yml and manifest-op.yml files:

    - name: node-hello-world
      memory: 100M
      path: web
      env:
        destinations: >
                      [
                        {"name":"ui5", "url":"https://ui5.sap.com"}
                      ]

    Destination service

    Destination configuration can also be read from destination service .
    Here are the Approuter limitations to destination properties configuration from destination service :

    Property Additional Property Description
    Type only HTTP supported.
    Authentication All authentication types are supported.
    Note: User and Password are mandatory if the authentication type is basic authentication.
    Note: if the authentication type set to principal propagation the ProxyType have to be on-premise.
    Note: if the authentication type set to OAuth2SAMLBearerAssertion, uaa.user scope in xs-security.json is required.
    ProxyType Supported proxy type : on-premise, internet, private-link.
    Note: if ProxyType set to on-premise, binding to SAP Cloud Platform connectivity service is required.
    Note: The private-link proxy type is a beta feature and is not meant for productive use. It is only available in Azure landscapes.
    Optional additional properties:
    Property Additional Property Description
    HTML5.ForwardAuthToken x If true the OAuth token will be sent to the destination. The default value is false. This token contains user identity, scopes and other attributes. It is signed by the UAA so it can be used for user authentication and authorization with backend services.
    Note: if ProxyType set to on-premise, ForwardAuthToken property should not be set.
    Note: if Authentication type is other than NoAuthentication, ForwardAuthToken property should not be set.
    HTML5.Timeout x Positive integer representing the maximum wait time for a response (in milliseconds) from the destination. Default is 30000ms.Note: The timeout specified will also apply to the destination's logout path or service's logout path (if you have set one).
    HTML5.PreserveHostHeader x If true , the application router preserves the host header in the backend request.
    This is expected by some back-end systems like AS ABAP, which do not process x-forwarded-* headers.
    HTML5.DynamicDestination x If true , the application router allows to use this destination dynamically on host or path level.
    HTML5.SetXForwardedHeaders x If true , the application router adds X-Forwarded-(Host, Path, Proto) headers to the backend request.Default value is true.
    sap-client x If provided, the application router propagates the sap-client and its value as a header in the backend request.
    This is expected by ABAP back-end systems.
    URL.headers.<header-name> x If provided, the application router propagates this special attribute in the destination as the header. The application router can get the headers list from the destination API. Existing request headers are not overwritten.


    Note:

    • In case destination with the same name is defined both in environment destination and destination service, the destination configuration will load from the environment.
    • Destinations on destination service instance level are supported.
    • Only destination client certificates of type p12 are supported.
    • Only destination trust certificates of the type privacy-enhanced mail (PEM) are supported.

    UAA configuration

    The User Account and Authentication (UAA) server is responsible for user authentication. In Cloud Foundry and XS OnPremise Runtime a service is created for this configuration and by using the standard service binding mechanism the content of this configuration is available in the VCAP_SERVICES environment variable. Note: The service should have xsuaa in its tags or the environment variable UAA_SERVICE_NAME should be specified (stating the exact name of the UAA service). During local development the UAA configuration is provided in the default-services.json file. When the UAA is used for authentication the user is redirected to the UAA's login page to enter their credentials.

    Sample content for a default-services.json file:

    {
        "uaa": {
            "url" : "http://my.uaa.server/",
            "clientid" : "client-id",
            "clientsecret" : "client-secret",
            "xsappname" : "my-business-application"
        }
    }

    The application router supports the $XSAPPNAME placeholder (upper case letters). You may use it in your route configurations in the scope property. The value of $XSAPPNAME is taken from the UAA configuration (the xsappname property).

    Additional headers configuration

    If configured, the application router can send additional http headers in its responses to the client. Additional headers can be set in the httpHeaders environment variable.

    Sample configuration for additional headers:

    [
      {
        "X-Frame-Options": "ALLOW-FROM http://localhost"
      },
      {
        "Test-Additional-Header": "1"
      }
    ]

    In this case, the application router sends two additional headers in the responses to the client.
    Custom response headers, configured in the application router configuration file (xs-app.json) are added to the list of additional http headers. If the response header name already exists in the additional http headers list, the value of the response header name overrides the value of the http header.

    Caution: For security reasons, the following headers must not be configured: authorization', 'cookie', and 'set-cookie'.

    Additional cookies configuration

    If configured, the application router will send additional cookie values in its responses to the client. Additional cookie values can be set in the COOKIES environment variable.

    Example of configuration for cookies in the manifest.yml :

      env:
       COOKIES: >
            { "SameSite":"None" }

    In this example, the application router sets the SameSite cookie attribute to None for the JSESSIONID cookie in the responses to the client.

    Note: Currently, only the SameSite cookie value is supported. SameSite = "Strict" is not supported.

    Plugins configuration

    A plugin serves almost the same purpose as routes. The difference is that plugins can be configured through the environment and that way you can add new routes to the application router without changing the design-time artefact xs-app.json. The plugin configuration properties are the same as those of a route except that you can't configure localDir, replace and cacheControl.

    Property Type Optional Description
    name String The name of this plugin
    source String/Object Describes a regular expression that matches the incoming request URL. Note: A request matches a particular route if its path contains the given pattern. To ensure the RegExp matches the complete path, use the following form: ^$`. Note: Be aware that the RegExp is applied to on the full URL including query parameters.
    target String x Defines how the incoming request path will be rewritten for the corresponding destination.
    destination String An alphanumeric name of the destination to which the incoming request should be forwarded.
    authenticationType String x The value can be ias, xsuaa, basic, or none. The default authenticationType depends on the authentication service binding: If the application router is bound to the Identity Authentication service, the default authenticationType is ias. Otherwise, the default value is xsuaa. If xsuaa or ias are used, the specified authentication server (Identity Authentication or User Account and Authentication) handles the authentication (the user is redirected to the login form of Identity Authentication or User Account and Authentication). The basic authenticationType works with SAP HANA users, SAP ID service, and Identity Authentication service. For more information, see the SAP Note 3015211 - BASIC authentication options for SAP BTP Cloud Foundry applications. If the value none is used, no authentication is required for this route.
    .
    csrfProtection Boolean x Enable CSRF protection for this route. The default value is true.
    scope Array/String/Object x Scopes are related to the permissions a user needs to access a resource. This property holds the required scopes to access the target path. Access is granted if the user has at least one of the listed scopes. Note: Scopes are defined as part of the xsuaa service instance configuration. You can use ias as authenticationType and xsuaa scopes for authorization if the application router is bound to both (ias and xsuaa)."

    Sample content of the plugins environment variable:

    [
      {
        "name": "insecurePlugin",
        "source": "/plugin",
        "destination": "plugin",
        "target": "/",
        "csrfProtection": false,
        "scope": ["viewer", "reader"]
      },
      {
        "name": "publicPlugin",
        "source": "/public-plugin",
        "destination": "publicPlugin",
        "authenticationType": "none"
      }
    ]

    Session timeout configuration

    For example, if you have the following line in your manifest.yml or manifest-op.yml file:

    - name: node-hello-world
      memory: 100M
      path: web
      env:
        SESSION_TIMEOUT: 40

    After 40 minutes of user inactivity (no requests have been sent to the application router), a Central Logout will be triggered due to session timeout.

    Note: The application router depends on the UAA server for user authentication, if the authenticationType for a route is xsuaa. The UAA server may have a different session timeout configured. It is recommended that the configurations of the application router and the UAA are identical.

    X-Frame-Options configuration

    Application router sends X-Frame-Options header by default with value SAMEORIGIN. This behaviour can be changed in 2 ways:

    • Disable sending the default header value by setting SEND_XFRAMEOPTIONS environment variable to false
    • Override the value to be sent via additional headers configuration

    Cross-Origin Resource Sharing configuration

    The CORS keyword enables you to provide support for cross-origin requests, for example, by allowing the modification of the request header. Cross-origin resource sharing (CORS) permits Web pages from other domains to make HTTP requests to your application domain, where normally such requests would automatically be refused by the Web browser's security policy. Cross-origin resource sharing(CORS) is a mechanism that allows restricted resources on a webpage to be requested from another domain (/protocol/port) outside the domain (/protocol/port) from which the first resource was served. CORS configuration enables you to define details to control access to your application resource from other Web browsers. For example, you can specify where requests can originate from or what is allowed in the request and response headers.

    The CORS configuration can be provided in the CORS environment variable or in the CORS property of the application router configuration file (xs-app.json). If a cross-origin resource sharing (CORS) configuration exists in both the environment variables and the application router configuration file (xs-app.json), the application router gives priority to the CORS configuration in the application router configuration file.

    The CORS configuration is an array of objects. Here are the properties that a CORS object can have:

    Property Type Optional Description
    uriPattern String A regular expression representing for which source routes CORS configuration is applicable. To ensure the RegExp matches the complete path, surround it with ^ and $. Defaults: none.
    allowedOrigin Array A comma-separated list of objects that each one of them containing host name, port and protocol that are allowed by the server.for example: [{?host?: "www.sap.com"}] or [{?host?: ?.sap.com?}]. Note: matching is case-sensitive. In addition, if port or protocol are not specified the default is ?__?. Defaults: none.
    allowedMethods Array of upper-case HTTP methods x Comma-separated list of HTTP methods that are allowed by the server. Defaults: [?GET?, ?POST?, ?HEAD?, ?OPTIONS?] (all) applies. Note: matching is case-sensitive.
    maxAge Number x A single value specifying how long, in seconds, a preflight response should be cached. A negative value will prevent CORS Filter from adding this response header to pre-flight response. Defaults: 1800.
    allowedHeaders Array of headers x Comma-separated list of request headers that are allowed by the serve. Defaults: [?Origin?, ?Accept?, ?X-Requested-With?, ?Content-Type?, ?Access-Control-Request-Method?, ?Access-Control-Request-Headers?].
    exposeHeaders Array of headers x Comma-separated list of response headers (other than simple headers) that can be exposed. Defaults: none.
    allowedCredentials Boolean x A flag that indicates whether the resource supports user credentials. Defaults: true.

    Sample content of the CORS environment variable:

    [
      {
          "uriPattern": "^\route1$",
          "allowedMethods": [
            "GET"
          ],
          "allowedOrigin": [
            {
              "host": "my_example.my_domain",
              "protocol": "https",
              "port": 345
            }
          ],
          "maxAge": 3600,
          "allowedHeaders": [
            "Authorization",
            "Content-Type"
          ],
          "exposeHeaders": [
            "customHeader1",
            "customHeader2"
          ],
          "allowedCredentials": true
        }
    ]

    It is also possible to include the CORS in the manifest.yml and manifest-op.yml files:

    - name: node-hello-world
      memory: 100M
      path: web
      env:
        CORS: >
          [
            {
              "allowedOrigin":[
                                {
                                    "host":"my_host",
                                    "protocol":"https"
                                }
                              ],
              "uriPattern":"^/route1$"
            }
          ]

    For route with source that match the REGEX ?^\route1$?, the CORS configuration is enabled.

    Direct Routing URI Patterns configuration

    With the direct routing URI patterns configuration, you can define a list of URIs that are directed to the routing configuration file (xs-app.json file) of the application router instead of to a specific application's xs-app.json file that is stored in the HTML5 Application Repository. This configuration improves the application loading time and monitoring options because it prevents unnecessary calls to the HTML5 Application Repository.

    The configuration is an array of strings or regular expressions. Note that the following regular expressions are preconfigured in the configuration array: "^favicon.ico$", "^login$". Therefore, do not name your HTML5 applications "favicon.ico" or "login"!

    You have to provide only the first segment in the URL, after the approuter host. For example, for the URL https://approuter-host/route1/index.html, you enter "route1" in the direct routing URI patterns array.

    Sample content of the Direct Routing URI Patterns environment variable:

      env:
        DIRECT_ROUTING_URI_PATTERNS: >
          ["route1", "^route2$", "route3"]

    NodeJS Minimal Logging Level configuration

    With this configuration, you can set the minimal logging level of the cf-nodejs-logging-support library of the application router. The following levels are available:

    • off

    • error

    • warn

    • info

    • verbose

    • debug

    • silly

    The default value is "error".

    Here is a sample content for the NodeJS minimal logging level environment variable:

      env:
        CF_NODEJS_LOGGING_LEVEL: "debug"

    Note The application router also uses the @sap/logging library. To configure the log level for this library, you use the XS_APP_LOG_LEVEL environment variable.

    Dynamic Identity Provider configuration

    If dynamicIdentityProvider is true, the end user can set the identity provider (IDP) for the application’s login process by filling the request query parameter sap_idp with the IDP Origin Key. If IdentityProvider property is defined in the route, its value will be overwritten by the sap_idp query parameter value. The default value for dynamicIdentityProvider is false. This configuration is relevant for a standalone approuter scenario and it is set for all routes.

    Here is a sample content for the dynamic identity provider environment variable:

      env:
        DYNAMIC_IDENTITY_PROVIDER: true

    Routes

    A route is a configuration that instructs the application router how to process an incoming request with a specific path.

    Property Type Optional Description
    source String/Object Describes a regular expression that matches the incoming request URL. Note: A request matches a particular route if its path contains the given pattern. To ensure the RegExp matches the complete path, use the following form: ^$`. Note: Be aware that the RegExp is applied to on the full URL including query parameters.
    httpMethods Array of upper-case HTTP methods x Which HTTP methods will be served by this route; the methods supported are: DELETE, GET, HEAD, OPTIONS, POST, PUT, TRACE, PATCH (no extension methods are supported). If this option is not specified, the route will serve any HTTP method.
    target String x Defines how the incoming request path will be rewritten for the corresponding destination or static resource.
    destination String x The name of the destination to which the incoming request should be forwarded. The destination name can be a static string or a regular expression that defines how to dynamically fetch the destination name from the source property or from the host.
    service String x The name of the service to which the incoming request should be forwarded.
    endpoint String x The name of the endpoint within the service to which the incoming request should be forwarded. Can only be used in a route containing a service attribute.
    localDir String x Folder in the working directory from which the application router will serve static content Note: localDir routes support only HEAD and GET requests; requests with any other method receive a 405 Method Not Allowed.
    preferLocal Boolean x Defines from which subaccount the destination is retrieved. If preferLocal is true, the destination is retrieved from the provider subaccount. If preferLocal is false or undefined, the destination is retrieved from the subscriber subaccount.
    replace Object x An object that contains the configuration for replacing placeholders with values from the environment. It is only relevant for static resources. Its structure is described in Replacements.
    authenticationType String x The value can be xsuaa,ias, basic or none. The default one is ias, if subaccount trusts an ias tenant, else xsuaa. When xsuaa or ias are used the specified authentication server will handle the authentication (the user is redirected to the authentication service login form). The basic mechanism works with SAP HANA users, SAP ID Service and SAP Identity Authentication service. Find more details in SAP Note 3015211 - BASIC authentication options for SAP BTP Cloud Foundry applications. If none is used then no authentication is needed for this route.
    csrfProtection Boolean x Enable CSRF protection for this route. The default value is true.
    scope Array/String/Object x Scopes are related to the permissions a user needs to access a resource. This property holds the required scopes to access the target path.
    cacheControl String x String representing the value of the Cache-Control header, which is set on the response when serving static resources. By default the Cache-Control header is not set. It is only relevant for static resources.
    identityProvider String x The name of the identity provider to use if provided in route’s definition. If not provided, the route will be authenticated with the default identity provider. Note: If the authenticationType is set to Basic Authentication or None, do not define the identityProvider property.
    dynamicIdentityProvider Boolean x If dynamicIdentityProvider is true, the end user can set the identity provider (IDP) for the application’s login process by filling the request query parameter sap_idp with the IDP Origin Key. If IdentityProvider property is defined in the route, its value will be overwritten by the sap_idp query parameter value. The default value for dynamicIdentityProvider is false.

    Note: The properties destination, localDir and service are optional, but exactly one of them must be defined.
    Note: When using the property replace it is mandatory to define the localDir property.
    Note: The cacheControl property is effective only when one of the following settings is performed:

    • The localDir property was set
    • A service pointing to HTML5 Application Repository ("service": "html5-apps-repo-rt") was set

    Example routes

    For example, if you have a configuration with the following destination:

    [
      {
        "name" : "app-1",
        "url" : "http://localhost:3001"
      }
    ]

    Here are some sample route configurations:

    • Route with a destination and no target
    {
        "source": "^/app1/(.*)$",
        "destination": "app-1"
    }

    Since there is no target property for that route, no path rewriting will take place. If we receive /app1/a/b as a path, then a request to http://localhost:3001/app1/a/b is sent. The source path is appended to the destination URL.

    • Route with case-insensitive matching
    {
        "source": {
          "path": "^/app1/(.*)$",
          "matchCase": false
        },
        "destination": "app-1"
    }

    This example is much like the previous one, but instead of accepting only paths starting with /app1/, we accept any variation of app1's case. That means if we receive /ApP1/a/B, then a request to http://localhost:3001/ApP1/a/B is sent. Note: The property matchCase has to be of type boolean. It is optional and has a default value true.

    • Route with a destination and a target
    {
        "source": "^/app1/(.*)$",
        "target": "/before/$1/after",
        "destination": "app-1"
    }
    • Route with a service, a target and an endpoint
    {
         "source": "^/odata/v2/(.*)$",
         "target": "$1",
         "service": "com.sap.appbasic.country",
         "endpoint": "countryservice"
    }

    When a request with path /app1/a/b is received, the path rewriting is done according to the rules in the target property. The request will be forwarded to http://localhost:3001/before/a/b/after.

    Note: In regular expressions there is the term capturing group. If a part of a regular expression is surrounded with parenthesis, then what has been matched can be accessed using $ + the number of the group (starting from 1). In the last example $1 is mapped to the (.*) part of the regular expression in the source property.

    • Route with dynamic destination and target
    {
          "source": "^/destination/([^/]+)/(.*)$",
          "target": "$2",
          "destination": "$1",
          "authenticationType": "xsuaa"
        }

    If you have a another destination configured:

    [
    	{
    	"name" : "myDestination",
    	"url" : "http://localhost:3002"
    	}
    ]

    when a request with the path /destination/myDestination/myTarget is received, the destination will be replaced with the url from "myDestination", the target will get "myTarget" and the request will be redirected to http://localhost:3002/myTarget

    Note: You can use a dynamic value (regex) or a static string for both destination and target values

    Note: The approuter first looks for the destination name in the mainfest.yaml file, and if not found, looks for it in the destination service.

    • Destination In Host

    For legacy applications that do not support relative URL paths, you need to define your URL in the following way to enable the destination to be extracted from the host the url should be defined in the following way:

    https://<tenant>-<destination>.<customdomain>/<pathtofile>

    To enable the application router to determine the destination of the URL host, a DESTINATION_HOST_PATTERN attribute must be provided as an environment variable.

    Example: When a request with the path https://myDestination.some-approuter.someDomain.com/app1/myTarget is received, the following route is used:

     {
          "source": "^/app1/([^/]+)/",
          "target": "$1",
          "destination": "*",
          "authenticationType": "xsuaa"
     }

    In this example, the target will be extracted from the source and the ‘$1’ value is replaced with ‘myTarget’. The destination value is extracted from the host and the ‘*’ value is replaced with ‘myDestination’.

    • Route with a localDir and no target
    {
        "source": "^/web-pages/(.*)$",
        "localDir": "my-static-resources"
    }

    Since there is no target property for that route, no path rewriting will take place. If we receive a request with a path /web-pages/welcome-page.html, the local file at my-static-resources/web-pages/welcome-page.html under the working directory will be served.

    • Route with a localDir and a target
    {
        "source": "^/web-pages/(.*)$",
        "target": "$1",
        "localDir": "my-static-resources"
    }

    If we receive a request with a path '/web-pages/welcome-page.html', the local file at 'my-static-resources/welcome-page.html' under the working directory will be served. Note: The capturing group used in the target property.

    • Route with localDir and cacheControl
    {
      "source": "^/web-pages/",
      "localDir": "my-static-resources",
      "cacheControl": "public, max-age=1000,must-revalidate"
    }
    • Route with service "html5-apps-repo-rt" and cacheControl
    {
      "source": "^/index.html$",
      "service": "html5-apps-repo-rt",
      "authenticationType": "xsuaa",
      "cacheControl":"public,max-age=1000,must-revalidate"
    }
    • Route with httpMethods restrictions

    The httpMethods option allows you to split the same path across different targets depending on the HTTP method. For example:

    {
      "source": "^/app1/(.*)$",
      "target": "/before/$1/after",
      "httpMethods": ["GET", "POST"]
    }

    This route will be able to serve only GET and POST requests. Any other method (including extension ones) will get a 405 Method Not Allowed response. The same endpoint can be split across multiple destinations depending on the HTTP method of the requests:

    {
      "source": "^/app1/(.*)$",
      "destination" : "dest-1",
      "httpMethods": ["GET"]
    },
    {
      "source": "^/app1/(.*)$",
      "destination" : "dest-2",
      "httpMethods": ["DELETE", "POST", "PUT"]
    }

    The setup above will route GET requests to the target dest-1, DELETE, POST and PUT to dest-2, and any other method receives a 405. It is also possible to specify "catchAll" routes, namely those that do not specify httpMethods restrictions:

    {
      "source": "^/app1/(.*)$",
      "destination" : "dest-1",
      "httpMethods": ["GET"]
    },
    {
      "source": "^/app1/(.*)$",
      "destination" : "dest-2"
    }

    In the setup above, GET requests will be routed to dest-1, and all the rest to dest-2.

    Why using httpMethods? It is often useful to split the implementation of microservices across multiple, highly specialized applications. For example, a Java application written to serve high amounts of GET requests that return large payloads is implemented, sized, scaled and load-tested differently than applications that offer APIs to upload limited amounts of data. httpMethods allows you to split your REST APIs, e.g., /Things to different applications depending on the HTTP methods of the requests, without having to make the difference visible in the URL of the endpoints.

    Another usecase for httpMethods is to "disable" parts of the REST API. For example, it may be necessary to disable some endpoints that accept DELETE for external usage. By allowing only certain methods in the route, you can hide functionalities of your microservice that should not be consumable without having to modify the code or configurations of your service.

    Note: localDir and httpMethods are incompatible. The following route is invalid:

    {
      "source": "^/app1/(.*)$",
      "target": "/before/$1/after",
      "localDir": "resources",
      "httpMethods": ["GET", "POST"]
    }

    However, since localDir supports only GET and HEAD requests, returning 405 to requests with any other method, any localDir route is "implicitly" restricted in terms of supported HTTP methods.

    • Route with a scope

    An application specific scope has the following format:

    <application-name>.<scope-name>
    

    It is possible to configure what scope the user needs to possess in order to access a specific resource. Those configurations are per route.

    In this example, the user should have at least one of the scopes in order to access the corresponding resource.

    {
        "source": "^/web-pages/(.*)$",
        "target": "$1",
        "scope": ["$XSAPPNAME.viewer", "$XSAPPNAME.reader", "$XSAPPNAME.writer"]
    }

    For convenience if our route requires only one scope the scope property can be a string instead of an array. The following configuration is valid as well:

    {
        "source": "^/web-pages/(.*)$",
        "target": "$1",
        "scope": "$XSAPPNAME.viewer"
    }

    You can configure scopes for the different HTTP methods (GET, POST, PUT, HEAD, DELETE, CONNECT, TRACE, PATCH and OPTIONS). If some of the HTTP methods are not explicitly set, the behaviour for them is defined by the default property. In case there is no default property specified and the HTTP method is also not specified, the request is rejected by default.

    {
        "source": "^/web-pages/(.*)$",
        "target": "$1",
        "scope": {
          "GET": "$XSAPPNAME.viewer",
          "POST": ["$XSAPPNAME.reader", "$XSAPPNAME.writer"],
          "default": "$XSAPPNAME.guest"
        }
    }

    The application router supports the $XSAPPNAME placeholder. Its value is taken (and then substituted in the routes) from the UAA configuration. You may read more about it here. Note: The substitution is case sensitive.

    You can use the name of the business application directly instead of using the $XSAPPNAME placeholder:

    {
        "source": "^/backend/(.*)$",
        "scope": "my-business-application.viewer"
    }
    • Route with an identityProvider

    For example, we can define several identity providers for different types of users. In this example, there are 2 categories: hospital patients and hospital personnel:

    1. patientsIDP – use for authenticating patients.
    2. hospitalIDP – use for authenticating all hospital personnel (doctors, nurses etc..).

    We can configure 2 routes with the following identityProvider properties:

    [
        { 
    	"source": "^/patients/sap/opu/odata/(.*)",
    	"target": "/sap/opu/odata$1",
    	"destination": "backend",
    	"authenticationType": "xsuaa",
    	"identityProvider": "patientsIDP"
        },
        {
    	"source": "^/hospital/sap/opu/odata/(.*)",
    	"target": "/sap/opu/odata$1",
    	"destination": "backend", "authenticationType": "xsuaa",
    	"identityProvider": "hospitalIDP"
        }
    ]

    So, a patient who tries to log into the system will be authenticated by patientIDP, and a doctor who tries to log in will be authenticated by hospitalIDP.

    Note: After logging in using one of the identity providers, to switch to the other one it is necessary to logout and perform a new log in.

    Note: Currently, dynamic provisioning of the subscriber account identity provider is not supported.

    Note: Identity provider configuration is only supported in the client side login redirect flow.

    • Route with a dynamicIdentityProvider

    For example, we can define a route where the value of identityProvider is patientsIDP and where dynamic identity provider provisioning is enabled by setting dynamicIdentityProvider to true:

    [
        { 
            "source": "^/patients/index.html",
            "target": "/patients-index.html",
            "service": "html5-apps-repo-rt",
            "identityProvider": "patientsIDP",
            "dynamicIdentityProvider": true
        }
    ]

    In this example, the patientsIDP value for the identityProvider is replaced by hospitalIDP if a request with sap_idp=hospitalIDP is executed, for example, if the request is https://shiva.health-center-approuter.cfapps.hana.ondemand.com/healthreport/patients/index.html?sap_idp=hospitalIDP.

    Replacements

    This object configures the placeholder replacement in static text resources.

    Property Type Description
    pathSuffixes Array An array containing the path suffixes that are relative to localDir. Only files with a path ending with any of these suffixes will be processed.
    vars Array A list with the environment variables that will be replaced in the files matching the suffix.
    services Object An object describing bound services that will provide replacement values. Each property of this object is used to lookup a separate service. The property names are arbitrary. Service lookup format is described in Service Query section in @sap/xsenv documentation.

    The supported tags for replacing environment variables are: {{ENV_VAR}} and {{{ENV_VAR}}}. If there is such an environment variable it will be replaced, otherwise it will be just an empty string.

    For services you can specify a property from the credentials section of the service binding which will be replaced. For example {{{my_service.property}}} and {{my_service.property}}

    Every variable that is replaced using two-brackets syntax will be HTML-escaped.

    For example if the value of the environment variable is ab"cd the result will be ab&amp;quot;cd. The triple brackets syntax is used when the replaced values don't need to be escaped and all values will be unchanged.

    For example, if somewhere in your xs-app.json you have a route:

    {
      "source": "^/get/home(.*)",
      "target": "$1",
      "localDir": "resources",
      "replace": {
        "pathSuffixes": ["index.html"],
        "vars": ["escaped_text", "NOT_ESCAPED"],
        "services": {
          "my-sapui5-service": {
            "tag": "ui5"
          }
        }
      }
    }

    and you have the following index.html:

    <html>
      <head>
        <title>{{escaped_text}}</title>
        <script src="{{{NOT_ESCAPED}}}/index.js"/>
        <script src="{{{my-sapui5-service.url}}}"/>
      </head>
    </html>

    then in index.html, {{escaped_text}} and {{{NOT_ESCAPED}}} will be replaced with the values of the environment variables escaped_text and NOT_ESCAPED.

    If you have a service in VCAP_SERVICES like:

    {
      "sapui5_service": [{
        "name": "sapui5",
        "tags": ["ui5"],
        "credentials": {
          "url": "http://sapui5url"
        }
      }]
    }

    then {{{my-sapui5-service.url}}} will be replaced with the url property from sapui5 service - in this case http://sapui5url.

    Note: All index.html files will be processed. If you want to replace only specific files, you have to set the path of the file relative to localDir.

    Note: All files should be UTF-8 encoded.

    Note: If a service is not found an error is thrown on startup.

    Note: If a service and an environment variable from vars have the same name, an error is thrown on startup.

    The returned content type is based on the file extension. Currently the supported file extensions are:

    • .json - application/json
    • .txt - text/plain
    • .html - text/html
    • .js - application/javascript
    • .css - test/css

    If the file extension is different, the default content type is text/html.

    Example for pathSuffixes:

    {
      "pathSuffixes": [".html"]
    }

    The suffix .html means that all files with the extension .html under localDir and it's subfolders will be processed.

    {
      "pathSuffixes": ["/abc/main.html", "some.html"]
    }

    The suffix /abc/main.html means that all files named main.html which are inside a folder named abc will be processed.

    The suffix some.html means that all files which have a name that ends with some.html will be processed. For example: some.html, awesome.html.

    {
      "pathSuffixes": ["/some.html"]
    }

    The suffix /some.html means that all files which have the exact name some.html will be processed. For example: some.html, /abc/some.html.

    Note: URL path parameters are not supported for replacements. For example, replacements will not work if the path looks like '/test;color=red/index.html'. For more information regarding path parameters refer to http://tools.ietf.org/html/rfc3986#section-3.3.

    xs-app.json configuration file

    This is the main configuration file of the application router. It contains a JSON object with the following properties:

    Property Type Optional Description
    welcomeFile String x The client is redirected to this page by default, if the request does not have a path. For more information, see welcomeFile.
    authenticationMethod String x If set to none the UAA login roundtrip is disabled. If the property is not set and authentication is defined per route, the value is set to route by default.
    sessionTimeout Number x Used to set session timeout. The default is 15 minutes. If the SESSION_TIMEOUT environment variable is set this property will be overwritten.
    routes Array x Contains all route configurations. The position of a configuration in this array is of significance for the application router in case a path matches more than one source. The first route whose source matches the path of the incoming request gets activated.
    login Object x Contains the configuration for the endpoint of the application router which will be used by the UAA during the OAuth2 authentication routine. By default this endpoint is /login/callback.
    logout Object x Provides options for a Central Logout endpoint and a page to which the client to be redirected by the UAA after logout.
    destinations Object x Additional options for your destinations (besides the ones in the destinations environment variable).
    services Object x Additional options for your business services.
    responseHeaders Array x Contains the optional response headers configuration.
    compression Object x Configuration regarding compressing resources before responding to the client. If the COMPRESSION environment variable is set it will overwrite existing values.
    pluginMetadataEndpoint String x Adds an endpoint that will serve a JSON representing all configured plugins.
    whitelistService Object x Options for the allowlist service preventing clickjack attacks.
    websockets Object x Options for the web socket communication.
    errorPage Array x Optional configuration to set-up a custom error pages whenever the approuter encouters an error.
    cors Array x Contains the configuration for cross-origin resource sharing.

    welcomeFile property

    Approuter will redirect to this URL when /(root path) is requested. This could be a file located inside the static resources folder or a resource hosted at a different location.

    Note: Approuter will serve the content of the resource instead of returning a redirect if the request contains a x-csrf-token: fetch header. See CSRF Protection.

    Example:

    "welcomeFile": "/web-pages/hello-world.html"

    web-pages has to be a part of a local resource or an external destination

    {
        "source": "^/web-pages/(.*)$",
        "localDir": "my-static-resources"
    }

    or

    {
        "source": "^/web-pages/(.*)$",
        "target": "$1",
        "destination": "mydest"
    }

    Note: If there isn't a route with a localDir property, the folloing default is added to the list of routes:

    {
      "source": "^/(.*)$",
      "localDir": "resources"
    }

    authenticationMethod property

    It may have the following values:

    • none - disables authentication for all routes
    • route - authentication type is defined in the route configurations

    The default value is route.

    routes property

    It holds an array of route configuration objects. The order of the configurations is important for the application router. The first route whose source pattern gets matched with the path of the incoming request will be activated. See Routes for more info.

    login property

    A redirect to the application router at a specific endpoint takes place during OAuth2 authentication with UAA. This endpoint can be configured in order to avoid possible collisions. For example:

    "login": {
      "callbackEndpoint": "/custom/login/callback"
    }

    The default endpoint is /login/callback.

    logout property

    In this object you can define your business application's central logout endpoint through the logoutEndpoint property. The value of logout property should be an object with the following properties:

    Property Type Optional Description
    logoutPath String The path to be used when logging out from application router.
    logoutPage String x The logout page url path.
    logoutMethod String x Could be POST or GET. The default value is GET.
    csrfProtection Boolean x Can only be defined if logoutMethod is POST. If logoutMethod is POST and this property is not defined, default is true. It can be set to false – for example if csrfProtection is implemented in backend application.

    For example, if somewhere in your xs-app.json you have:

    "logout": {
      "logoutEndpoint": "/my/logout"
    }

    This will open an endpoint on application router which, when requested, will trigger the central logout routine. Changing the browser location from the client-side JavaScript code:

    window.location.replace('/my/logout');

    will trigger client initiated central Logout.

    In addition, a page to which the user will be redirected by the UAA after logout can be configured using the logoutPage property. It may hold:

    • URL path - the UAA will redirect the user back to the application router and the path will be interpreted according the configured routes.

    The logoutEndpoint can be called with query parameters. For example:

    window.location.replace('/my/logout?siteId=3');

    These parameters will be appended as is to the redirect url set by the logoutPage property. For example, if the logout section is the following:

    "logout": {
        "logoutEndpoint": "/logout",
        "logoutPage": "/logoff.html"
      },
    

    The redirect url will end with:

    /logoff.html?siteId=3
    

    Note: The resource that matches the path should not require authentication. The property authenticationType should be set to none for that particular route.

    Example:

    {
      "authenticationMethod": "route",
      "logout": {
        "logoutEndpoint": "/my/logout",
        "logoutPage": "/logout-page.html"
      },
      "routes": [
        {
          "source": "^/logout-page.html$",
          "localDir": "my-static-resources",
          "authenticationType": "none"
        }
      ]
    }

    In this case my-static-resources (contains logout-page.html) is a folder with static resources in the working directory of the application router.

    Note: Be sure that your main route in your xs-app.json resource that matches the path is not cached by browser. Therefore, the best practice here would be to model cacheControl accordingly:

    {
      "routes": [
        {
          "source": "^/ui/index.html",
          "target": "index.html",
          "localDir": "web",
          "cacheControl": "no-cache, no-store, must-revalidate"
        }
      ]
    }
    • Absolute http(s) URL - the UAA will redirect the user to a page (or application) different from the application router. For example:
    "logout": {
      "logoutEndpoint": "/my/logout",
      "logoutPage": "http://employees.portal"
    }

    Note: UAA will execute redirect only in case redirect URL is a valid redirect-uri in xs-security.json - redirect-uris are maintained as part of the oauth2-configuration section in the UAA application security descriptor JSON file given at the creation of the service instance. For example:

    UAA application security descriptor:

    "oauth2-configuration": {    
        "redirect-uris":
        [
         "http://employees.portal"
        ]    
    }
    

    Using POST method for Logout

    For security reasons it is recommended to model the logout flow using "POST" method and enable CSRF protection.

    In that case, logoutMethod and csrfProtection parameters should be added in logout property:

      "logout": {
        "logoutEndpoint": "/my/logout",
        "logoutPage": "/logout-page.html",
        "logoutMethod": "POST",
        "csrfProtection": true
    }

    Note: For backward compatibility reasons logoutMethod default value is GET. The csrfProtection property can only be set if logoutMethod is POST. If logoutMethod is POST and csrfProtection property is not set, csrfProtection will be enabled by default.

    Consumption example: The POST request should be an AJAX request and include CSRF token.

    async function getToken() {
      return new Promise((resolve) => {
      jQuery.ajax({
        type: "GET",
        url: 'my/logout',
        headers: {
          "X-CSRF-Token": 'fetch',
          contentType: "application/json",
        },
        success: function(data, textStatus, request){
          resolve(request.getResponseHeader('X-CSRF-Token'));
        },
       });
     });
    };
    

    POST request example:

    const token = await getToken();
    jQuery.ajax({
      type: "POST",
      url: "my/logout",
      headers: {
        "X-CSRF-Token": token,
        contentType: "application/json",
      },
      success: function (data) {
        window.location.href = data;
      }
    });
    

    Note: Make sure that url field matches logoutEndpoint.

    destinations property

    Let's say you have a destination called node-backend. You can specify options for it by adding the destinations property in your xs-app.json:

    "destinations": {
      "node-backend": {}
    }

    The value of node-backend should be an object with the following properties:

    Property Type Optional Description
    logoutPath String x The logout endpoint for your destination.
    logoutMethod String x Could be POST, PUT, GET. The default value is POST.

    The logoutPath will be called when Central Logout is triggered or a session is deleted due to timeout. The request to the logoutPath will contain additional headers, including the JWT token. The logoutMethod property specifies the HTTP method with which the logoutPath will be requested. For example:

    {
      "destinations": {
        "node-backend": {
          "logoutPath": "/ui5logout",
          "logoutMethod": "GET"
        }
      }
    }

    services property

    Let's say you have a service called com.sap.appbasic.country. You can specify options for it by adding the services property in your xs-app.json:

    "services": {
      "com.sap.appbasic.country": {}
    }

    The value of com.sap.appbasic.country should be an object with the following properties:

    Property Type Optional Description
    endpoint String x The name of the attribute in the VCAP_SERVICES that contains the URL of the service.
    logoutPath String x The path to be used when logging out from the service.
    logoutMethod String x Could be POST, PUT, GET. The default value is POST.

    The logoutPath will be called when Central Logout is triggered or a session is deleted due to timeout. The request to the logoutPath will contain additional headers, including the JWT token in header authorization and approuter host in header x-approuter-host. The logoutMethod property specifies the HTTP method with which the logoutPath will be requested. For example:

    {
      "services": {
        "com.sap.appbasic.country": {
          "endpoint": "countryservice",
          "logoutPath": "/countrieslogout",
          "logoutMethod": "GET"
        }
      }
    }

    responseHeaders property

    With the custom response header property, you can add headers, which the application router returns to the client in its responses.
    The property is an array of objects, each object having the following properties:

    Property Type Optional Description
    name String response header name
    value String response header value

    Example:

    { "responseHeaders" : [
        {"name": "header1", "value": "value1"},
        {"name": "header2", "value": "value2"}
      ]
    }

    compression property

    By default text resources are compressed before being sent to the client. The default threshold for using compression is 1K. Text resources under this size will not be compressed. If you need to change the compression size threshold, you can add the optional property minSize.

    Here is an example of a compression section (2048 bytes):

    {
      "compression": {
          "minSize": 2048
      }
    }
    Property Type Optional Description
    minSize Number x Text resources larger than this size will be compressed.
    enabled Boolean x Globally disables or enables compression. Default value is true.
    compressResponseMixedTypeContent Boolean x Determines whether response content of multipart/mixed content type should be compressed. The default value is false.

    Note: There are 3 ways to disable compression:

    • Global - within the compression section add "enabled": false
    • Front-End - the client sends a header Accept-Encoding which omits gzip
    • Backend - the application sends a header Cache-Control with the 'no-transform' directive

    Example of globally disabling compression using the environment variable COMPRESSION:

    {
      "enabled": false
    }

    Note: The header field Content-Length is used to determine the resource size. If Content-Length is missing, the chunk size is used to determine whether to compress the resource. For more information, see the npm module compression.

    Here is a complete example of the compression environment variable:

      env:
       COMPRESSION: >
            { 
    	  "enabled": true,
    	  "minSize": 2048,
    	  "compressResponseMixedTypeContent": true
    	  }

    pluginMetadataEndpoint property

    Example:

    {
      "pluginMetadataEndpoint": "/metadata"
    }

    Note: If you request relative path /metadata of your application, you will receive a JSON with configured plugins.

    whitelistService property

    The whitelistService property is used for enabling the allowlist service that prevents clickjack attacks. An endpoint accepting GET requests will be opened at the relative path configured in the endpoint property. For more details see Allowlist service section.

    Example:

    {
      "whitelistService": {
        "endpoint": "/whitelist/service"
      }
    }

    websockets property

    For more details about the web socket communication see Web sockets section.

    Example:

    {
      "websockets": {
        "enabled": true
      }
    }

    To use Websockets when approuter is integrated with HTML5 Application Repository, this property should be added to the xs-app.json of the deployed HTML5 application. When an incoming request for an application in the repository goes through approuter, approuter retrieves the application's configuration from the repository. If this flag is set, approuter creates a websockets connection with the backend (the target url of the request) and acts as a proxy which delivers messages on top of ws protocol from the backend to the user and vice versa.

    errorPage property

    By default, errors originating in the application router are shown the status code of the error. It is also possible to display a custom error page using the errorPage property.

    The property is an array of objects, each object having the following properties:

    Property Type Optional Description
    status Number/Array HTTP status code
    file String File path relative to the working directory of the application router

    Example:

    { "errorPage" : [
        {"status": [400,401,402], "file": "./custom-err-40x.html"},
        {"status": 501, "file": "./http_resources/custom-err-501.html"}
      ]
    }

    In the example above 400, 401 and 402 errors would be shown the content of ./custom-err-4xx.html and for 501 errors the user would see ./http_resources/custom-err-501.html.

    Note: The errorPage conifiguration section has no effect on errors generated outside of the application router.

    cors property

    With the cors property, you can support cross-origin requests.
    If a cross-origin resource sharing (CORS) configuration exists in both the environment variables and the application router configuration file (xs-app.json), the application router gives priority to the CORS configuration in the application router configuration file.
    For more information about the CORS configuration see Cross-Origin Resource Sharing configuration.

    Complete example of an xs-app.json configuration file

    Without HTML5 Application Repository integration:

    {
      "welcomeFile": "index.html",
      "authenticationMethod": "route",
      "sessionTimeout": 10,
      "pluginMetadataEndpoint": "/metadata",
      "routes": [
        {
          "source": "^/sap/ui5/1(.*)$",
          "target": "$1",
          "destination": "ui5",
          "csrfProtection": false
        },
        {
          "source": "/employeeData/(.*)",
          "target": "/services/employeeService/$1",
          "destination": "employeeServices",
          "authenticationType": "xsuaa",
          "scope": ["$XSAPPNAME.viewer", "$XSAPPNAME.writer"],
          "csrfProtection": true
        },
        {
          "source": "^/(.*)$",
          "target": "/web/$1",
          "localDir": "static-content",
          "replace": {
            "pathSuffixes": ["/abc/index.html"],
            "vars": ["NAME"]
          }
        }
      ],
      "login": {
        "callbackEndpoint": "/custom/login/callback"
      },
      "logout": {
        "logoutEndpoint": "/my/logout",
        "logoutPage": "/logout-page.html"
      },
      "destinations": {
        "employeeServices": {
          "logoutPath": "/services/employeeService/logout",
          "logoutMethod": "GET"
        }
      },
      "compression": {
        "minSize": 2048
      },
      "whitelistService": {
        "endpoint": "/whitelist/service"
      },
      "websockets": {
        "enabled": true
      },
      "errorPage": [
        {"status": [400,401,402], "file": "/custom-err-4xx.html"},
        {"status": 501, "file": "/custom-err-501.html"}
      ]
    }

    With HTML5 Application Repository integration (xs-app.json file stored in HTML5 Application Repository):

    {
      "welcomeFile": "index.html",
      "authenticationMethod": "route",
      "routes": [
        {
          "source": "/employeeData/(.*)",
          "target": "/services/employeeService/$1",
          "destination": "employeeServices",
          "authenticationType": "xsuaa",
          "scope": ["$XSAPPNAME.viewer", "$XSAPPNAME.writer"],
          "csrfProtection": true
        },
        {
           "source": "^/odata/v2/(.*)$",
           "target": "$1",
           "service": "com.sap.appbasic.country",
           "endpoint": "countryservice"
        },
        {
          "source": "^(/.*)$",
          "target": "$1",
          "service": "html5-apps-repo-rt",
          "authenticationType": "xsuaa"
        }
      ],
      "logout": {
        "logoutEndpoint": "/my/logout",
        "logoutPage": "/logout-page.html"
      },
      "destinations": {
        "employeeServices": {
          "logoutPath": "/services/employeeService/logout",
          "logoutMethod": "GET"
        }
      },
      "services": {
        "com.sap.appbasic.country": {
          "logoutPath": "/countryService/logout",
          "endpoint": "countryservice",
          "logoutMethod": "GET"
        }
      }
    }

    Note: The route in bold is the route that provides access to the HTML5 Application Repository service.

    Headers

    Forwarding Headers

    The application router passes the following x-forwarding-* headers to the route targets:

    Header Name Description
    x-forwarded-host Contains the Host header which was sent by the client to the application router.
    x-forwarded-proto Contains the protocol which was used by the client to connect to the application router.
    x-forwarded-for Contains the address of the client which connects to the application router.
    x-forwarded-path Contains the original path which was requested by the client.

    If a client performs a path rewriting, it sends the x-forwarded-proto, x-forwarded-host, and the x-forwarded-path headers to the application router. The values of these headers are forwarded to the route targets without modifications instead of being generated from the application router request URL. The x-forwarded-path header of a request does not impact the source pattern of routes in the xs-app.json.

    Hop-by-hop Headers

    Hop-by-hop headers are meaningful only for a single transport-level connection and therefore are not forwarded by the application router. These headers are:

    • Connection
    • Keep-Alive
    • Public
    • Proxy-Authenticate
    • Transfer-Encoding
    • Upgrade

    Custom Headers

    • x-custom-host: Contains the internal reverse proxy host. Relevant only if the application router is used behind an internal reverse proxy as well as an external reverse proxy (EXTERNAL_REVERSE_PROXY environment variable is set to true). Add this header to the request to internal reverse proxy.

    In a multi-tenancy landscape, the application router will calculate the tenant id based on the value of a certain request header as follows:

    • x-custom-host header or host if EXTERNAL_REVERSE_PROXY is true
    • x-forwarded-host header or host if EXTERNAL_REVERSE_PROXY is false or not specified

    Authorization Header

    • Bearer: contains the JSON Web Token (JWT) or Open ID Connect (OIDC) access token.
    • Basic: contains a Base64 encoded set of user/password. Note that Application Router uses these credentials to create a Bearer token using the password grant flow.

    CSRF Protection

    By default the application router enables CSRF protection for any HTTP method that is not HEAD or GET and the route is not public. A path is considered public, if it does not require authentication. This is the case for routes with authenticationType: none or if authentication is disabled completely via the top level property authenticationMethod: none.

    To obtain a CSRF token one must send a GET or HEAD request with a x-csrf-token: fetch header to the application router. The application router will return the created token in a x-csrf-token: <token> header, where <token> will be the value of the CSRF token.

    If a CSRF protected route is requested with any of the above mentioned methods, x-csrf-token: <token> header should be present in the request with the previously obtained token. This request must use the same session as the fetch token request. If the x-csrf-token header is not present or invalid, the application router will return status code 403 Forbidden and a response header x-csrf-token: Required.

    Support of SAP Statistics

    The application router provides performance statistics in an HTTP response header in the following cases:

    • The HTTP request contains an HTTP query parameter (URL parameter) sap-statistics=true.
    • The HTTP request contains an HTTP header field sap-statistics:true.

    If an HTTP request that contains a header field or query parameter with "sap-statistics=true" reaches the application router, the application router forwards an "sap-statistics" header to the corresponding backend. If SAP statistics is implemented for the backend, the backend returns to the application router a response header containing the statistics information from the backend.

    The application router returns the following statistics information in an sap-statistics-approuter response header:

    • total: The time that has passed between the moment when the request entered into the application router and the moment when the application router started writing the response
    • ext (in case of destination forwarding): The time spent in the backend

    Each backend sub-component can add its own response header with the duration measurements when it receives the HTTP header sap-statistics:true.

    Connectivity

    The application router supports integration with SAP Cloud Platform connectivity service. The connectivity service handles proxy access to SAP Cloud Platform cloud connector, which tunnels connections to private network systems. In order to use connectivity, a connectivity service instance should be created and bound to the Approuter application. In addition, the relevant destination configurations should have proxyType=OnPremise. Also, a valid XSUAA login token should be obtained via the login flow.

    SaaS Application Registration in Cloud Foundry

    The application router supports SaaS registration. A SaaS business application based on application router may be registered in the SaaS registry by creating and binding a SaaS Registry service instance. After fulfilling the CIS process to enable application subscription, the SaaS business application will be visible in the SAP Cloud Platform cockpit in the Cloud Foundry environment for all entitled customers. Once a customer is entitled to the SaaS business application, the subaccounts (tenants) created under the global account will be able to view, subscribe to, and unsubscribe from the application. When a tenant is subscribed/unsubscribed to/from an application, the tenant will be subscribed/unsubscribed:

    • In the XSUAA instance of the application itself
    • In the reuse services (e.g.: destination ), if the application is dependent on the reuse service. Also, onboarding and offboarding callbacks will be triggered for the subscribed/unsubscribed application and for the reuse services.

    If you use IAS by binding a multi-tenant application router to an identity service instance, the subscription manager service (SMS) should be used to enable the subscription to a subscriber zone and an IAS tenant.

    How To Expose Approuter for SaaS Subscription

    Multi-tenancy

    The application router should be configured to handle multi-tenant access by maintaining the TENANT_HOST_PATTERN environment configuration.

    Entitle org for SaaS Application consumption

    The SaaS Registry service and / or the Subscription Manager service should be available in your space marketplace.

    Authorize LPS for invoking callbacks

    SaaS business applications should grant LPS the authorization to invoke the application's callbacks. Callback scope should be granted to LPS in the application router’s xs-security.json file:

    xs-security.json:

    ...
     {  
        "name":"$XSAPPNAME.Callback",
        "description":"With this scope set, the callbacks for tenant onboarding, 
         offboarding and getDependencies can be called.",
             "grant-as-authority-to-apps":[  
                "$XSAPPNAME(application,sap-provisioning,tenant-onboarding)"
             ]
      }
    ...  
    

    Authentication with Identity Service (IAS)

    To use IAS authentication an identity service instance of plan application should be created with the following configuration:

    {
       "oauth2-configuration": {
         "redirect-uris": ["https://*.<landscapeDomain>/login/callback?authType=ias"],  //Enable redirect after login
         "post-logout-redirect-uris": ["https://*.<landscapeDomain>/*/logout.html" ]    //Enable redirect after logout
       },
       "xsuaa-cross-consumption":true, //Enable xsuaa trust
       "multi-tenant":true //enable multitenancy
    }
    

    Authentication with IAS should be performed using X.509 certificates. To achieve this the identity service should be bound to approuter using the following configuration:

    {
      "credential-type": "X509_GENERATED"
     }
    

    Register an application in SaaS Registry (SaaS Registry Configuration)

    For a customer to be able to subscribe to an application through the SAP Cloud Platform cockpit, each SaaS business application should register itself on all CF landscapes where it is deployed.

    To register a SaaS application in LPS, a service instance of saas-registry should be created and the SaaS business application should be bound to it. The instance of saas-registry is created with a configuration json - saas-config.json:. In the configuration.json file a url for the getDependencies and onSubscription callbacks must be provided. Note that the path segment of these urls are configurable however the tenantId url variable in onSubscription callback must be provided anyway.

    {
    	"appId" : "<appId>",  # xsappname generated by XSUAA - can be obtained by checking the xsuaa-> xsappname by executing: cf env <application name>
    	"appName" : "<appName>",  # Business application name to be shown to subscribers 
    	"appUrls": { 
    		"getDependencies" : "<approuter-host>/callback/v1.0/dependencies",
    	    "onSubscription" : "<approuter-host>/callback/v1.0/tenants/{tenantId}" 
    	},
    	"providerTenantId" : "<tenant>"  # Approuter provider account tenant ID.
    }   
    
    

    Register an application in Subscription Manager (Subscription Manager Configuration)

    To register an SaaS application in the subscription manager service, a service instance of the subscription manager has to be created and the SaaS business application has to be bound to it. The instance of subscription manager is created with a configuration json file - sms-config.json:. In the configuration.json file, a url for the getDependencies callbacks and the onSubscription callbacks must be provided. Note that the path segments of these urls are configurable.

    {
      "iasServiceInstanceName" : ["ias-provider-ias"], #Name of the related IAS instance
      "applicationType": "application",
      "xsuaaSaasApplicationServiceInstanceId": "88afb2a5-5ab3-409a-9c0c-b70e2b86b1cf", #SaaS Registry service instance id
      "appCallbacks" : {
        "dependenciesCallbacks" : {
          "url" : "https://<providerZoneId>--<providerIASTenantId>.<approuterHost>.cert.<landscapeDomain>/v1.0/callback/zones/{zoneId}/dependencies"
        },
        "subscriptionCallbacks" : {
          "url" : "https://<providerZoneId>--<providerIASTenantId>.<approuterHost>.cert.<landscapeDomain>/v1.0/callback/zones/{zoneId}"
        }
      }
    }
    

    Note that in order to provide certificates the url domain should contain a "cert" segment. In addition the TENANT_HOST_PATTERN environment variable should be modified to support requests with the "cert" segment. For example:

    ^(.*).<approuterHost>.(cert.)?<landscapeDomain>
    

    Mutual TLS Authentication (mTLS) and Certificates Handling

    Application router supports certificates usage for token creation and mTLS handshake in backend connections. To enable that the XSUAA or IAS instance bound to the application router should provide in its credentials a certificates chain and a private key

    Note that application router also supports providing private key via environment variables: XSUAA_PRIVATE_KEY (XSUAA) and IAS_PRIVATE_KEY (IAS).

    In case certificates and private key exists, application router fetches XSUAA/IAS tokens providing certificates chain and private key. When forwarding request to business services, application router also uses certificates to create a client_credentials token or exchange the login token.

    If certificates available, HTTP connection to backend is created using private key and a concatenation of intermediate and client certificates, enabling mTLS handshake.

    Cloud Foundry: client certificate is propagated via the x-forwarded-client-cert header. In order to enable that the backend url should contain a .cert segment in its domain.

    Integration with HTML5 Application Repository

    The application router supports seamless integration with the HTML5 Application Repository service. When the application router interacts with HTML5 Application Repository to serve HTML5 Applications, all static content and routes (xs-app.json) are retrieved from HTML5 Application Repository. In case application router needs to route to non HTML5 Applications, it is possible to model that in the xs-app.json of the application router.

    To integrate HTML5 Application Repository to an application router based it is required to create an instance of html5-apps-repo service of plan app-runtime and bind it to the application. xs-app.json routes that are used to retrieve static content from HTML5 Application Repository may be modeled in the following format:

     { 
         "source": "^(/.*)",                                    
         "target": "$1",                                        
         "service": "html5-apps-repo-rt", 
         "authenticationType": "xsuaa"                      
     }
    

    HTML5 Application Repository Multitenancy

    The HTML5 Application Repository is a multitenant service. Non-public HTML5 Applications are visible only to the application providers (with provider subaccounts) and the consumers subscribed to the applications (with consumer subaccounts).

    When a multitenant application router is subscribed to a subaccount, the HTML5 Application Repository app-runtime instance that is bound to the application router is returned as a dependency, which triggers the subscription to the app-runtime instance. You can also bind HTML5 Application Repository app-host service instances to the application router to enable the subscription of the corresponding HTML5 applications. During runtime, the application router creates an HTML5 Application Repository app-runtime client_credentials token using the tenant URL that the application router determines from the TENANT_HOST_PATTERN environment variable.

    Note: The creation of the token can fail if the app-runtime instance is not subscribed to the subaccount, which happens if, for example, the application router was subscribed to the subaccount before the HTML5 Application Repository became a multitenant service. In this case the application router will create the token using the provider subaccount.

    You can trigger the subscription to the HTML5 Application Repository app-runtime instance by using the SAAS Provisioning API: see https://api.sap.com/api/APISaasManagerService/resource

    PATCH /saas-manager/v1/application/tenants/{tenantId}/subscriptions
    

    Note: If you have an old application router version, the HTML5 Application Repository app-runtime client_credentials token is created by using HTML5 application provider subaccount.

    Blocked HTML5 Application Names

    The following strings are used as predefined direct routing URIs, which lead the request to the routing configuration file of the application router: "favicon.ico", "login". Therefore, do not name your HTML5 applications "favicon.ico" or "login"!

    Known Gaps in Integration with HTML5 Application Repository

    The following limitations apply when application router is bound to HTML5 Application Repository service:

    1. It is not possible to implement the "first" middleware slot to provide routes dynamically.
    2. No option apart from workingDir can be provided in application router start.
    3. External session management via extensibility is not supported

    Note: Mixed scenario of modeling part of the static content in local resources folder and also retrieving static content from HTML5 Application Repository is not supported. Note: This feature is only supported in Cloud Foundry. There is no HTML5 Application Repository service in XSA.

    Runtime Processing

    During runtime, based on request url path (see URL Format), application router will try to fetch the xs-app.json file from the corresponding HTML5 Application in HTML5 Application Repository and use it for routing the request. The following algorithm is applied for request processing:

    • If no HTML5 Application is found in HTML5 Application Repository for current request, central application router xs-app.json will be used for routing
    • If HTML5 Application exists in HTML5 Application Repository but no xs-app.json file is returned, an error message will be issued and request processing will be stopped.

    URL Format

    A valid request to application router that uses HTML5 Application Repository must have the following format:

    https://<tenantId>.<appRouterHost>.<domain>/<bsPrefix>.<appName-appVersion>/<resourcePath>
    
    

    bsPrefix (business service prefix) - Optional

    • It should be used in case the application is provided by a business service bound to this approuter

    appName (application name) - Mandatory

    • Used to uniquely identify the application in HTML5 Application Repository persistence
    • Must not contain dots or special characters

    appVersion (application version) - Optional

    • Used to uniquely identify a specific application version in HTML5 Application Repository persistence
    • If no version provided, default application version will be used

    resourcePath (path to file)

    • The path to the file as it was stored in HTML5 Application Repository persistence

    Query Parameters:

    skipXSAppJsonCache - Optional

    • Value: true
    • Supports skipping the usage of cache when getting the xsApp configuration, bringing it remotely and re-setting the cache.
    • Note that the query parameter is removed from request url before route processing.

    Cache Buster Handling

    A cache buster allows the application router to notify the browser to refresh the resources only when the application resources have been changed. Otherwise the resources are always fetched from the browser's cache. This flow applies to requests that should be forwarded to HTML5 Application Repository. If requests are forwarded to backend applications that return data, cache buster handling is not applied.

    • When the second path segment of the request url contains the pattern “timestamp”, this segment is removed from the subsequent request to HTML5 Application Repository
    • In case the request had a cache buster segment, application router adds to corresponding response the header: Cache-Control: public, max-age=31536000

    Note: Cache buster flow is only supported in HTML5 Application Repository integration flow.

    Integration with Business Services

    Application router supports integration with Business Services. Business Services are a flavour of reuse-services that expose specific information in VCAP_SERVICES credentials block that enable application router to serve Business Service UI and/or data.

    • Business Service UI must be stored in HTML5 Application Repository to be accessible from application router
    • Business Service UI must be defined as "public" to be accessible from an application router in a different space than the one from where the UI was uploaded
    • Business Service data can be served using two grant types:
      1. User Token Grant: Application router performs a token exchange between login JWT token and Business Service token and uses it to trigger a request to the Business Service endpoint
      2. Client Credentials Grant: Application router generates a client_credentials token and uses it to trigger a request to the Business Service endpoint

    Business Service Credentials

    While binding a Business Service instance to application router the following information should be provided in VCAP_SERVICES credentials:

    • sap.cloud.service: Service name as referenced from xs-app.json route and business service prefix (if Business Service UI provided) - Mandatory
    • sap.cloud.service.alias: Short service name alias for user friendly URL business service prefix- Optional
    • endpoints: One or more endpoints that can be used to access Business Service data.
    • html5-apps-repo: html5-apps-repo.app_host_id contains one or more html5-apps-repo service instance GUIDs that can be used to retrieve Business Service UIs - Optional
    • saasregistryenabled: flag that indicates that this Business Service supports SaaS Registry subscription. If provided, application router will return this Business Service xsappname in SaaS Registry getDependencies callback - Optional
    • grant_type: the grant type that should be used to trigger requests to the Business Service. Allowed values: user_token or client_credentials. Default value, in case this attribute is not provided, user_token - Optional
    • forwardiastoken: flag that indicates if, in addition to the exchanged xsuaa token, the IAS token should be forwarded as well. IAS token is forwarded in request header: x-ias-token

    The value of endpoints should be an object with the following properties:

    Property Type Optional Default Description
    url String URL to access the Business Service data.
    timeout Number x 30000ms Positive integer representing the maximum wait time for a response (in milliseconds) from the Business Service.

    For example:

    "country": [
       {
        ...
        "credentials": {
         "sap.cloud.service": "com.sap.appbasic.country", 
         "sap.cloud.service.alias": "country",            
         "endpoints": {                                   
          "countryservice": { "url": https://icf-countriesapp-test-service.cfapps.sap.hana.ondemand.com/odata/v2/countryservice"},
          "countryconfig":  { 
                "url": https://icf-countriesapp-test-service.cfapps.sap.hana.ondemand.com/rest/v1/countryconfig",
                "timeout": 120000 
          }
         },
         "html5-apps-repo": {                           
          "app_host_id": "1bd7c044-6cf4-4c5a-b904-2d3f44cd5569, 1cd7c044-6cf4-4c5a-b904-2d3f44cd54445"
         },
         "saasregistryenabled": true,
         "grant_type": "user_token"
       ....
    

    Accessing Business Service Data

    To access Business Service data xs-app.json configuration file should have a route referencing a specific sap.cloud.service or sap.cloud.service.alias via the service attribute. If an endpoint attribute is also modeled, it will be used to get the service url otherwise the fallback url or uri attribute will be used.

    For example:

    "routes": [
        {
          "source": "^/odata/v2/(.*)$",
          "target": "$1",
          "service": "com.sap.appbasic.country",
          "endpoint": "countryservice"
        },
    
    

    In order to support JWT token exchange, the login JWT token should contain the uaa.user scope. For that the xs-security configuration must contain a role template that references the uaa.user scope. For example:

    {
        "xsappname"   : "simple-approuter",
        "tenant-mode" : "shared",
        "scopes": [
            {
                "name": "uaa.user",
                "description": "UAA"
            },
            {
                "name": "$XSAPPNAME.simple-approuter.admin",
                "description": "Simple approuter administrator"
            }
        ],
        "role-templates": [
            {
                "name": "Token_Exchange",
                "description": "UAA",
                "scope-references": [
                    "uaa.user"
                ]
            },
            {
                "name": "simple-approuter-admin",
                "description": "Simple approuter administrator",
                "scope-references": [
                    "$XSAPPNAME.simple-approuter.admin"
                ]
            }
        ]
    }
    

    Accessing Business Service UI

    Business Service UI's must be stored in HTML5 Application Repository and defined in their manifest.json files as "public: true" in order to be accessible from an application router application that is typically running in a different space than the Business Service space. In addition dataSources uris must be relative to base url (no slash as first character).

    Business Service manifest.json example:

    {
      “sap.app”: {
        “id”:“com.sap.appbasic.country.list”,
        “applicationVersion: {
        “version”: “1.0.0”
      },
      "dataSources": {
        "mainService":{
          "uri": "odata/v2/countryservice",
          "type": "OData"
        }
      },
      “sap.cloud”: {
        "public": true,
        “service”: “com.sap.appbasic.country“
      }
    }
    

    A Business Service that exposes UI must provide one or more app-host GUIDs in an html5-apps-repo block in VCAP_SERVICES credentials (see Business Service credentials).

    To access Business Service UI the request url that hits application router must contain a business service prefix as described above.

    Request URL example:

      https://approuter-repo-examples.cfapps.sap.hana.ondemand.com/comsapappbasiccountry.comsapappbasicscountrylist/test/flpSandbox.html
    
    

    In this example "comsapappbasiccountry" is the business service prefix which matches the sap.cloud.service attribute in country service VCAP_SERVICES credentials (without dots). The "comsapappbasicscountrylist" is the name of the HTML5 Application as defined in the app.id attribute in the manifest.json (without dots).

    Web Sockets

    The application router is capable of forwarding web socket communication. In order to use the web socket communication, it should be enabled through the websockets property. If the backend service requires authentication then the upgrade request should contain a valid session cookie. The destination schemas "ws" and "wss" are supported in addition to "http" and "https". When the application router receives an upgrade request, it verifies that the Origin header holds the URL of the application router. If this is not the case, then an HTTP response with status 403 is returned to the client. This origin verification can be further configured via the environment variable WS_ALLOWED_ORIGINS. It contains the allowed origins the application router verifies against. It's structure is the same as CJ_PROTECT_WHITELIST.

    Note: A current limitation is that a web socket ping is not forwarded to the backend service.

    Session Handling

    The application router establishes a session with the client (browser) using a session cookie.

    The application router intercepts all session cookies, sent by backend services and stores them in its own session. Backend session cookies are not sent to the client in order to prevent cookie collisions. Upon subsequent requests the application router sends back the cookies to the respective backend services so they can establish their own sessions. Note: Non-session cookies from backend services are forwarded to the client. Cookie collisions may occur and the application should be able to handle them.

    If a pending request is canceled, the request cancellation will be propagated to the backend service.

    If there is no session in the application router, either because there has been a session timeout or because no session has been created yet, and if the incoming request matches a non-public route, the application router triggers a redirect to the authentication service (UAA or IAS). After a successful login, a redirect back to application router takes place using the login callback endpoint, which triggers the creation of a new session. If the incoming request is an AJAX request (has the request header X-Requested-With: XMLHttpRequest) or if the HTTP verb is not GET and no session exists (there is no session cookie and the request doesn’t have an x-approuter-authorization header), the application router returns the response code 401 - Unauthorized. This enables the client application to handle the 401 response before it navigates to the authentication service. For example, the application can store data entered by the user and prevent data loss. When the handling of the 401 response is completed, the client application should send a request without an xmlhttprequest object to trigger the application router authentication flow.

    Session Contents

    • CSRF token - the generated CSRF token so it can be verified against the token in the request, see CSRF Protection above.
    • OAuth token - JSON Web Token (JWT) fetched from UAA and forwarded to backend services in the Authorization header. The client never gets this token. The application router refreshes the JWT automatically before it expires (if the session is valid). By default this routine is triggered 5 minutes before the expiration of the JWT. This can also be configured via the JWT_REFRESH environment variable (the value is in minutes). If JWT_REFRESH is set to 0 then the refresh is disabled.
    • OAuth scopes - scopes owned by the current user, used to check if the user has the scope required for each request. See scope in Routes.
    • Backend session cookies - all session cookies sent by backend services.
    • Business Services OAuth tokens - JSON Web Token (JWT) exchanged and used to access re-use services bound to the application router

    Note: If the JWT is close to expiration and the session is still active a JWT refresh will be triggered in JWT_REFRESH minutes before expiration. JWT_REFRESH is an environment variable stating the number of minutes before the JWT expiration the refresh will be triggered. The default value is 5 minutes.

    External Session Management

    The application router supports a backup of user sessions in an external session store. This enables the session recovery in case the application router instance that stores a session crashes and another application router instance has to continue handling the running user session.
    To enable this capability, you must bind a service instance of a service that supports a fast persistence store, such as Redis. When such a service is bound, the application router backs up the in-memory session information into the external persistency store.
    If, in subsequent requests, the session information is not found in the in-memory session store, the application router tries to rebuild the in-memory session information from the external persistency store.

    The sessions are stored compressed. For capacity planning, you can assume 50 Kb per session storage in the fast persistence store.

    External Session Management Configuration

    In order to use this feature, you have to set the following environment variable:

    EXT_SESSION_MGT

    The variable value must be defined in the JSON format and provide the following properties:

    • instanceName (mandatory) - the name of the service instance of the storage service.
    • storageType (mandatory) - the type of the storage, for example - "redis". Note that if no custom storage driver is used, only “redis” is allowed.
    • sessionSecret (mandatory) - a secret to be used to generate a session cookie. Please generate a unique string with at least 64 characters.
    • defaultRetryTimeout - the maximum duration for automatic retries of failed Redis operations in milliseconds. The default value is 2000 ms.
    • backOffMultiplier - a multiplier of the Redis-defined pause that determines the time between consecutive automatic retries of failed Redis operations. The default value is 50.

    For example:

    {
        "instanceName": "approuter-redis",
        "storageType": "redis",
        "sessionSecret": "someuniquesessionsecret",
        "defaultRetryTimeout": 10000,
        "backOffMultiplier": 10
    }

    NOTE: Currently, the application router supports only a Redis store

    Configuration of a Custom Storage Driver

    For information about the configuration of a custom storage driver, see Configuring a custom storage driver

    Service to Application Router

    The application router can receive a consumer service JWT token created by the SAP Authorization and Trust Management (xsuaa) service or an OIDC access token created by Identity Authentication service and use it to access the UI and the data. The token is passed to the application router in the "x-approuter-authorization" header of the request. For more information, see Authorization Header.

    Cookie Handling: In this flow client cookies are merged to backend cookies in case a backend cookie with the same key does not exist.

    If you have configured external session management, an external session is created for each token in the external session management service (for example, in Redis). Such an external session has the same expiration time as the token for which it was created. The application router uses the external session to store cached data, such as the exchanged tokens and destination configurations, to improve the performance by reducing roundtrips to the authentication and destination services.

    Note: The XSUAA JWT token or the OIDC token are generated with the same XSUAA service instance or the same Identity service instance that is bound to the application router.

    Central Logout

    Central Logout can be client initiated or can be triggered due to session timeout.

    • Client initiated
      • Deletes the user session.
      • Requests all backend services logout paths (if configured in the destinations property).
      • Request all business services logout paths (if configured in the services property).
      • Redirects the client to logout from UAA.
      • If configured, redirects back to a custom page (for XS OnPremise Runtime only). For more information, see logout-property.
    • Session timeout
      • Deletes the user session.
      • Requests all backend services logout paths (if configured in the destinations property).
      • Requests all business services logout paths (if configured in the services property).

    The session timeout can be configured with the SESSION_TIMEOUT variable through the environment.

    Allowlist Service

    A protection concept is designed in SAP that uses UI libraries and an allowlist service for proper clickjack protection of applications. The general idea is that when an html page needs to be rendered in a frame, a check is done by calling the allowlist service to validate if the parent frame is allowed to render the content in a frame. The actual check is provided by the allowlist service.

    Enable the service

    To enable the allowlist service and to open the service endpoint you need to configure the whitelistService property in xs-app.json.

    Configuring allowed hostnames / domains

    The allowlist service reads allowed hostnames and domains from the environment variable CJ_PROTECT_WHITELIST. The content is a JSON array of object with the following properties:

    Property Type Optional Description
    protocol String x URI scheme, for example http.
    host String Hostname / domain - valid hostname, or domain defined with a star (*), for example some.concrete.hostname, or *.example.domain.
    port String / Number x Port string or number containing a valid port.

    Example:

    [
      {
        "protocol": "http",
        "host": "*.example.domain",
        "port": 12345
      },
      {
        "host": "some.concrete.hostname",
      }
    ]

    Matching is done against provided properties. For example if only host is provided then the service will return framing: true for all and matching will be for all schemas and protocols.

    Return value

    The service accepts only GET requests and the response is a JSON object. The allowlist service call uses the parent origin as URI parameter (URL encoded) as follows:

    GET url/to/whitelist/service?parentOrigin=https://parent.domain.com
    

    The response is a JSON object with following properties:

    {
        "version" : "1.0",
        "active"  : true | false,                   // indicates whether framing control is switched on
        "origin"  : "<same as passed to service>",
        "framing" : true | false                    // if active, describes if framing should be allowed
    }
    

    The property active will have value false only in case CJ_PROTECT_WHITELIST is not provided.

    Note: Keep in mind that the application router sends by default the X-Frame-Options header with value SAMEORIGIN, in the case the allowlist service is enabled, this header value probably needs to be changed, see the X-Frame-Options header section for details how to change it.

    User API Service

    The application router exposes a user API that returns the details of the user who is logged in. This API supports two endpoints: /currentUser and /attributes. The /currentUser endpoint returns all details of logged in users, while the /attributes endpoint returns the main user properties. The user API can be implemented by modelling an xs-app.json route using service sap-approuter-userapi.

    Note: The following applies if the route has the authentication type “xsuaa”:

    • User scopes from the xsuaa access token will be added to the response of both endpoints.
    • User attributes from the identity provider (IdP) chosen for the authentication will be added to the response of the “/attributes” endpoint. If a custom IdP is configured for Identity Authentication Service (IAS), the custom user attributes are also added to the response of the “/attributes” endpoint. For more information about the definition of custom properties in IAS, see Configure the Default Attributes Sent to the Application on the SAP Help Portal.
    • In order to get the user attributes from the custom IdP, the following property should be added to application router xs-security.json file - "foreign-scope-references": ["user_attributes"]

    Examples:

    Handle both endpoints

    {
        "source": "^/user-api(.*)",
        "target": "$1",
        "service": "sap-approuter-userapi"
    },
    

    Handle /currentUser endpoint only

    {
        "source": "^/user-api/currentUser$",
        "target": "/currentUser",
        "service": "sap-approuter-userapi"
    },
    

    The /currentUser endpoint response has the following format:

    {
       "firstname": "John",
       "lastname": "Doe",
       "email": "john.doe@sap.com",
       "name": "john.doe@sap.com",
       "displayName": "John Doe (john.doe@sap.com)",
       "scopes": "openid,user_attributes,uaa.user" (See the note above about routes with authentication type “xsuaa”.)
    }
    

    The /attributes endpoint response has the following format:

    {
       "firstname": "John",
       "lastname": "Doe",
       "email": "john.doe@sap.com",
       "name": "john.doe@sap.com",
       "scopes": "openid,user_attributes,uaa.user", (See the note above about routes with authentication type “xsuaa”.)
       <user attributes, including custom attributes> (See the note above about routes with authentication type “xsuaa”.)
    }
    

    Note that the "name" property is the user ID in the identity provider, which in many cases is also the email address.

    Scaling

    The application router keeps all established sessions in local memory and does not sync them across multiple instances. In order to scale the application router to multiple instances, session stickiness should be enabled. This means that each HTTP session is handled by the same application router instance.

    In Cloud Foundry's router, session stickiness is enabled from version 0.1.0.

    In SAP HANA XS Advanced OnPremise Runtime session stickiness is enabled, if SAP Web Dispatcher is used as a router. This is set by default from version 0.1535 of SAP HANA XS Advanced runtime. If your on-premise runtime uses nginx as router, you can switch to SAP Web Dispatcher by passing the command line option --router=webdispatcher to xs-controller.

    Sizing Guide for Application Router

    The memory consumption of the application router is described in the sizing guide.

    Configure server-side HTTPS

    You can configure application router to accept only HTTPS connections. See httpsOptions option of start function.

    Audit-Log Service

    The application router logs information regarding unauthorized requests. To avoid exposure of private information such as user id and IP address, you must bind the consuming application to an instance of the audit-log service.

    If you do not bind the consuming application to the audit-log service, the application router will log this information to the console output, using asterisks to mask the user id and IP address. (This is the default behavior.)

    Troubleshooting

    The application router uses @sap/logging package so all of its features are available to control logging. For example to set all logging and tracing to finest level set XS_APP_LOG_LEVEL environment variable to debug.

    If the application is deployed on Cloud Foundry, you can change the log level by running command:

    cf set-env <application-name> XS_APP_LOG_LEVEL debug

    If the application is deployed on XS Advanced On-premise Runtime, you can change the log level without restarting the application. For example this command will set all logging and tracing to finest level.

    xs set-logging-level <application-name> "*" debug

    See @sap/logging documentation for details.

    You can enable additional traces of the incoming and outgoing requests by setting the environment variable REQUEST_TRACE to true. When enabled they will log basic information for every incoming and outgoing request of the application router. This could have a performance impact.

    Some of the libraries used by this package employ other tracing mechanisms. For example many use the popular debug package. This means that by setting DEBUG environment variable, you can enable additional traces. Set it to * to enable all of them, but be careful as the output may be overwhelming. In addition internal Node.js traces can be enabled via NODE_DEBUG environment variable. This post describes it in more detail.

    Warning: Enabling some of these options may trace security sensitive data, so use with caution.

    The @sap/logging package sets the header 'x-request-id' in the application router's responses. This is useful if you would like to search entries belonging to a particular request execution in the application router's logs and traces. Note that the application router does not change the headers received from the backend and being forwarded to the client. If the backend is a Node.js application which uses the @sap/logging package (and also sets the 'x-request-id' header), then the value of the header that the client will receive will be the one coming from the backend and not the one of the application router itself.

    Getting Support

    Create a BCP ticket on component BC-XS-APR

    Extending Application Router

    See extending for information how to extend the application router with custom logic.

    Best practices

    Security best practices

    Content-Security-Policy

    Setting the Content-Security-Policy header - this is a response header which informs browsers (capable of interpreting it) about the trusted sources from which an application expects to load resources. This mechanism allows the client to detect and block malicious scripts injected into an application. A value can be set via the httpHeaders environment variable in the additional headers configuration. The value represents a security policy which contains directive-value pairs. The value of a directive is an allowlist of trusted sources. In case content-security-policy headers are returned from backend, they will override httpHeaders configuration. To enable returning both (backend and local content-security-policy headers), configure environment variable MERGE_CSP_HEADERS.

    Refer to the Content-Security-Policy specification for more information on the header's value.

    Note: Usage of the Content-Security-Policy header is considered second line of defense. An application should always provide proper input validation and output encoding.

    Identity Provider Configuration Best Practices

    Modelling options:

    1. If you to enable login in same browser window as doctor and patient you can create 2 cf routes to same approuter: https://approuter-doctors.cfapps.hana.com/myapp/doctors/index.html
    {
      "source": "^/doctors(/.*)",
      "target": "$1",
      "service": "html5-apps-repo-rt",
      "authenticationType": "xsuaa",
      "identityProvider": "doctorsIDP"
    }

    https://approuter-patients.cfapps.hana.com/myapp/patients/index.html

    {
      "source": "^/patients(/.*)",
      "target": "$1",
      "service": "html5-apps-repo-rt",
      "authenticationType": "xsuaa",
      "identityProvider": "patrientsIDP"
    }
    1. If you to enable single access at a time (force logout from doctors idp and re-login to patients idp), create a single cf route https://approuter-hospital.cfapps.hana.com/myapp/doctors/index.html
    {
      "source": "^/doctors(/.*)",
      "target": "$1",
      "service": "html5-apps-repo-rt",
      "authenticationType": "xsuaa",
      "identityProvider": "doctorsIDP"
    }

    https://approuter-hospital.cfapps.hana.com/myapp/patients/index.html

    {
      "source": "^/patients(/.*)",
      "target": "$1",
      "service": "html5-apps-repo-rt",
      "authenticationType": "xsuaa",
      "identityProvider": "patrientsIDP"
    }

    Keywords

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    Install

    npm i @sap/approuter

    DownloadsWeekly Downloads

    23,299

    Version

    11.5.0

    License

    SEE LICENSE IN LICENSE

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    Total Files

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