1.20.5 • Public • Published

    baucis v0.20.5

    Baucis enables you to build scalable REST APIs using the open source tools and standards you and your team already know. Like Baucis and Philemon of old, the module provides REST to the weary traveler. Baucis is not the same as Bacchus.

    Baucis is used in production by startups, departments, and at least one Fortune 500 company, not to mention at hackathons and conferences worldwide.

    If you like Baucis, please consider tipping.

    The official baucis documentation is being moved to but is still right here for the moment!


    • Awesomely scalable. Takes full advantage of the inherent power of Node.js and MongoDB.
    • Automatically build APIs through reflection of your Mongoose schemata.
    • Built on Express so adding custom middleware is a snap. 100% compatible with existing middleware such as passport.
    • Supports geolocation and full text search.
    • Highly customizable, simple interface. Can be extended with plugins.
    • Automatically generate interactive Swagger documentation for the API.
    • Perform rich queries of the API using an expressive JSON syntax via query string.
    • Mongoose middleware, inheritence, and validation methods are automatically respected.
    • Version your API using semver.
    • Over 150 Mocha.js tests.

    Coming Soon

    • Real time browser/client subscription with EventSource (server sent events)
    • Web hooks

    Check the change log for info on all the latest features.


    David Rjckaert III - Philemon and Baucis Giving Hospitality to Jupiter and Mercury

    David Rijckaert - Philemon and Baucis Giving Hospitality to Jupiter and Mercury

    Getting Started

    To install:

    npm install baucis

    An example of creating a REST API from a couple Mongoose schemata.

    var Vegetable = new mongoose.Schema({ name: String });
    var Fruit = new mongoose.Schema({ name: String });
    mongoose.model('vegetable', Vegetable);
    mongoose.model('fruit', Fruit);
    // Create a simple controller.'vegetable');
    // Create a controller with custom middleware for update/create.'fruit').request('put post', function (request, response, next) {
      if (request.isAuthenticated()) return next();
      return response.send(401);
    // Create the app and listen for API requests
    var app = express();
    app.use('/api', baucis());

    Later, make requests:

    HTTP Verb /vegetables /vegetables/:id
    GET Get all documents, or documents that match the query conditions. Get the addressed document.
    POST Creates new documents and sends them back. You can POST a single document or an array of documents. n/a
    PUT n/a Update the addressed document.
    DELETE Delete all documents, or documents that match the query conditions. Delete the addressed object.
    HEAD Check what headers would be returned for the given query without sending the request body. Check what headers would be returned for the instance returns an instance of the controller created to handle the schema's API routes. Pass in a mongoose model name:

    var controller ='robot');

    Or, pass in a Mongoose model:

    var controller ='robot'));

    Controllers are Express apps like any other.

    // Add middleware before API routes
    controller.use('/qux', function (request, response, next) {
      // Do something cool…
    controller.get('/readme', function (request, response, next) {
      // Send a readme document about the resource (for example)
    // Do other stuff...
    controller.set('some option name', 'value');

    Customize them with Express middleware, including pre-existing modules like passport. Middleware can be registered like so:

    controller.request(function (request, response, next) {
      if (request.isAuthenticated()) return next();
      return response.send(401);



    This property sets the controller's mongoose model. A string or model object may be passed in. The first time the model is set singular, plural, and path will also be set to defaults based on the mongoose model. The model property is initally set when the controller is first constructed.



    Customize the name used for singular instances of documents associated with this controller. Defaults to the name of the controller's model.



    Customize the name used for groups of documents associated with this controller. Defaults to the plural of the controller's singular name. Uses Mongoose's pluralizer utility method.


    Select or deselect fields for all queries.'foo +bar -password');


    Set to true to enable setting the response Link header with various useful links. Especially useful for paging.



    The unique path used to identify documents for this controller. Defaults to _id.



    Set the Last-Modified HTTP header using the given Date field. Disabl;ed by default.



    Enable optimistic locking. (Disabled by default.) Requires that all PUTs must send the document version (__v by default) and will send a 409 response if there would be a version conflict, instead of performing the update.



    Allow sending an index hint for the query from the client. Disabled by default.



    Allow sending a query comment from the client. Disabled by default.



    Used to disable specific HTTP methods for the controller.

    controller.methods('post put delete', false);


    BYPASSES VALIDATION Use this method to enable non-defualt update operators. The update method can be set using the X-Baucis-Update-Operator header field.

    controller.operators('$push $set', 'foo some.path some.other.path');
    controller.operators('$pull', 'another.path');


    This can be used to add paths under a controller. For example, a teacher schema might define an array of classrooms. controller.vivify lets embed the classrooms associated with a teacher at a URL like /teacher/123/classrooms.

    var teachers ='teacher');
    var classrooms = teachers.vivify('classrooms');


    This can be used to note the path the schema defines that is associated with a vivified URL. For example, in the above example, if the classroom schema didn't use the field teacher to link to the teachers collection, but instead used a name of classTeachers:

    var teachers ='teacher');
    var classrooms = teachers.vivify('classrooms').parentPath('classTeachers');


    Versioning is implemented using semver. Supported releases are specified when calling baucis(). The release(s) that a controller belongs to are specified with the versions controller option.'cat').versions('0.0.1');'cat').versions('>0.0.1 <1.0.0');'cat').versions('~1');'cat').versions('>2.0.0');
    app.use('/api', baucis({ releases: [ '0.0.1', '0.0.2', '1.0.0', '1.1.0', '2.0.0' ]}));

    Later, make requests and set the API-Version header to a semver range, such as ~1, >2 <3, *, etc. Baucis will use the highest release number that satisfies the range. If no API-Version is specified in a request, the highest release will be used.


    Baucis takes full advantage of Node streams internally to offer even more performance, especially when dealing with large datasets. Both outgoing and incoming documents are streamed!

    To alter or inspect documents being sent or process, add a through stream that transforms or processes them. As a shortcut, a map function can be passed in. It will be used to create a map stream internally. Here's an example of adding a stream to alter POST'd or PUT'd request bodies:

    controller.request(function (request, response, next) {
      request.baucis.incoming(function (context, callback) { = 'Feverfew';
        callback(null, context);

    For PUT requests, the document is available to the stream. For POSTs context.doc will be set to null.

    controller.request(function (request, response, next) {
      request.baucis.incoming(function (context, callback) {
        if (context.doc.created !== context.incoming.created) {
          callback(baucis.errors.Forbidden('The created date cannot be updated'));
        callback(null, context);

    Passing in through streams is also allowed. Here's an example using the through module to create a stream that checks for a forbidden sort of whiskey and alters the name of incoming (POSTed) documents.

    controller.request(function (request, response, next) {
      request.baucis.incoming(through(function (context) {
        if (context.incoming.whiskey === 'Canadian') {
          // Errors will be passed off to `next` later, and the stream will
          // be stopped.
          this.emit('error', baucis.errors.Forbidden('Too smooth.'));
        } = 'SHAZAM';

    If request.baucis.incoming or request.baucis.outgoing is called multiple times, the multiple through streams will be piped together.

    Here's an example of how a stream that interacts with outgoing documents may be added:

    controller.request(function (request, response, next) {
      request.baucis.outgoing(through(function (context) {
        if (context.doc.owner !== request.user) {
          // Errors will be passed off to `next` later, and the stream will
          // be stopped.
          this.emit('error', baucis.errors.Forbidden());
        delete context.doc.password;

    • For POSTs, if request.body is present, the incoming request will be parsed as a whole, negating many of the benefits of streaming. However, especially when POSTing only one new document at a time, this is not an issue. If you want to POST many objects at once, using the default streaming behavior is highly recommened.
    • If you set request.baucis.documents, this will be streamed out instead of the Mongoose query results.
    • The document stage of middleware has been deprecated. Use an outgoing through stream instead.


    Baucis adds middleware registration functions for two stages of the request cycle:


    This stage of middleware will be called after baucis applies defaults based on the request, but before the Mongoose query is generated.


    This stage of middleware will be called after baucis applies defaults to the Mongoose query object, but before the documents are streamed out through the response. The Mongoose query can be accessed and changed in your custom middleware via request.baucis.query. Query middleware cannot be added explicitly for POST and will be ignored when added for POST implicitly.

    How to use baucis middleware

    To apply middleware to all API routes, just pass the function or array to the method for the appropriate stage:

    controller.request(function (request, response, next) {
      if (request.isAuthenticated()) return next();
      return response.send(401);
    controller.query(function (request, response, next) {

    To add middleware that applies only to specific HTTP methods, use the second form. It adds a paramater that must contain a space delimted list of HTTP methods that the middleware should be applied to.

    controller.query('head get', function (request, response, next) {

    The final form is the most specific. The first argument lets you specify whether the middleware applies to document instances (paths like /cheeses/:id) or to collection requests (paths like /cheeses).

    controller.request('instance', 'head get del', middleware);
    controller.request('collection', 'post', middleware);


    Here's how to use swagger. First, install the plugin:

    npm install --save baucis-swagger

    Next, download the swagger-ui client.

    git clone
    open swagger-ui/dist/index.html

    Then, create your API as normal, but be sure to require baucis-swagger.

    var baucis = require('baucis');
    var swagger = require('baucis-swagger');
    app.use('/api', baucis());

    Point the swagger client at your API:


    Now you have documentation and a test client!

    To customize the swagger definition, simply alter the controler's swagger data directly:

    var controller ='sauce');
      'path': '/sauces/awesome',
      'description': 'Awesome sauce.',
      'operations': [
          'httpMethod': 'GET',
          'nickname': 'getAwesomeSauce',
          'responseClass': 'Sauce',
          'summary': 'Carolina BBQ Sauce.'

    HTTP Headers


    Header Field Notes
    API-Version Set this to a valid semver range to request a specific version or range of versions for the requested controller.
    X-Baucis-Update-Operator Use this to perform updates (that BYPASS VALIDATION) using a special update operator such as $set, $push, or $pull. The fields that may be updated must be whitelisted per controller.


    Header Field Notes
    ETag Used for HTTP caching based on response body. Supported automatically for single object endpoints.
    Last-Modified Used for HTTP caching. Can be set automatically by Baucis for single object endpoints.
    Accept Set to application/json for all responses.
    Allow Set automatically, correctly removing HTTP methods when those methods have been disabled.
    Location Set to the URL of the created/edited entity for PUT and POST responses.
    Link Optionally, baucis can add related links to the header for you. Especially useful for paging through a query. first, last, next, and previous links are added when paging through a collection when using the limit & skip query options.

    Query Options

    Use query options from the client to make dynamic requests. Query options can be mixed as you see fit.


    Set the Mongoose query's find or remove arguments. This can take full advtange of the MongoDB query syntax, using geolocation, regular expressions, or full text search. Special query operators are fine, and in fact geolocation, regular expression, and full text search capabilities are available to your API clients by default!

    GET /api/people?conditions={ "location": { "$near": [44, -97] } }
    GET /api/people?articles={ "summary": { "$text": "dog bites man" } }
    GET /api/cats?sort=-name&limit=1&conditions={ "features": "stripes" }
    DELETE /api/people?conditions={ "name": { "$regex": "^Bob W", $flags: "i" } }


    Skip sending the first n matched documents in the response. Useful for paging.

    GET /api/horses?skip=3


    Limit the response document count to n at maximum.

    GET /api/horses?limit=3

    If both limit and skip are used on a request, the response Link header will be set with extra relations that give URLs for paging.


    Sort response documents by the given criteria. Here's how you'd sort the collection by name in ascending order, then by age in descending order.

    GET /api/cheeses?sort=name -age


    Set which fields should be selected for response documents.

    GET /api/phones?select=-_id -year

    It is not permitted to use the select query option to select deselected paths. This is to allow a mechanism for hiding fields from client software.

    You can deselect paths in the Mongoose schema definition using select: false or in the controller by calling e.g.'-foo'). Your server middleware will be able to select these fields as usual using, while preventing the client from selecting the field.


    Set which fields should be populated for response documents. See the Mongoose population documentation for more information. The string or object syntax can be used:

    GET /api/boats?populate=captain
    GET /api/cities?populate={ "path": "captain", "match": { "age": "44" } }

    The select option of populate is disallowed. Only paths deselected at the model level will be deselected in populate queries.


    May be set to true for GET requests to specify that a count should be returned instead of documents

    GET /api/stereos?count=true


    Set to a path name to retrieve an array of distinct values.

    GET /api/restaurants?distinct=category


    Add an index hint to the query (must be enabled per controller).

    GET /api/pools?hint={ name: 1 }


    Add a comment to a query (must be enabled per controller).

    GET /api/wrenches?comment=Something informative

    Errors & Status Codes

    Baucis supports a rich array of error responses and status codes. For more information on status codes see RFC2616 the HTTP sepcification.


    4xx status codes mean that the client, for example a web browser made a mistake an needs to fix the response.

    400 Bad Request

    The client made a bad request and should fix the request before trying again. This is also sent when a deprecated command is used.


    403 Forbidden

    Sent when the requested action is disallowed for a controller.


    404 Not Found

    Sent when the query does not match any document, or when the requested resource does not exist.


    405 Method Not Allowed

    The request HTTP method (i.e one of HEAD, GET, POST, PUT, DELETE) is disabled for this resource. This can be done by e.g. controller.methods('post put del', false).


    406 Not Acceptable

    The Accept header specified in the request could not be fulfilled. By default JSON is supported. Baucis is pluggable to allow adding formatters for additional content types.


    409 Conflict

    If a controller has optimistic locking enabled, baucis will automatically check each updated document's version and give a 409 error if another API client modified the document before the requester was able to send their update.

    In this case, a client could reload the document, present the user with a description of the conflict, and ask them how to procede.


    415 Unspported Media Type

    The request body content type was not able to be parsed. By default JSON is supported. Baucis is pluggable to allow adding parsers for additional content types.


    422 Unprocessable Entity

    This status indicates a validation error ocurred, or that the entity sent to the server was invalid semantically in another way.


    Baucis will send a response body with error 422 that indicates what validation failed for which fields.

        "name": {
          "message": "Path `name` is required.",
          "name": "ValidatorError",
          "path": "name",
          "type": "required"
        "score": {
          "message": "Path `score` (-1) is less than minimum allowed value (1).",
          "name": "ValidatorError",
          "path": "score",
          "type": "min",
          "value": -1);

    Technically, this error is from RFC4918, the WebDAV specification.


    Where as 4xx errors mean the requester messed up, 5xx errors mean the server messed up :)

    500 Internal Server Error

    This means that baucis is misconfigured, or that the server tried to perform the requested action but failed.


    501 Not Implemented

    The requested functionality is not implemented now, but may be implented in the future.



    Q2 2014

    • v1.0.0 Release candidates
    • Improve documentation
    • Begin a cookbook-style guide with lots of code examples.
    • v1.0.0
    • Express 4


    The baucis-json plugin is bundled with baucis by default. It's a good example for writing your own plugins, and for parsing or outputting custom content types.


    © 2012-2014 William P. Riley-Land


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