cassandra-jpa

Javascript (Node.js) Persistence API (JPA) for Apache Cassandra

A persistence layer for using Apache Cassandra with Node.js based on the latest DataStax Cassandra Driver.

This module brings features from the Java World (JPA) and try to make life with Cassandra easier, mostly for people coming from the JAVA World.

The idea is to make the API as similar as possible to the latest JPA so that Java - and not only - developers to start easily with cassandra. Last but not least, this modules provides a good base for any Node.js developer for any kind of project that uses cassandra as its reposistory.

Installation

$ npm install cassandra-jpa

Prerequistics

• ES6 (Node.js > 4.1.0)
• CQL 3
• Compatible with Cassandra / Cassandra driver 3

Design

• Flexible configuration
• Datastax Cassandra Driver Configuration
• Configurable entity class, (TODO: allow for not having to extend - interface-like style)
• OOP using classes
• Self explainable Java (JPA) API based/inspired
• NODE.js best practices

Features

• Create, Drop Cassandra Tables programmatically
• Create Indexes
• Persist Javascript entities (JS Class extending Entity or Pure JS Objects)
• Remove Javascript entities
• Flexible configuration
• Datastax Cassandra Driver Configuration
• Configurable base entity class, (or use of Symbol as Interface still TODO)
• Logging through the debug module (set the environment variable DEBUG to cassandra-jpa)
• ES6 (Node.js > 4.0.0)
• OOP using classes
• Self explainable API
• Following NODE.js best practices

Basic usage

Import the cassandra-persistence module

let jpa = require('cassandra-jpa');

Create your Entity Class Extending (optionally, see baseEntityClass in the configuration) the base Entity

Requirements

• toJSON function should return entity property names same with table fields

See more in the foo example

Configure your persistence

configuration = new jpa.JPAConfiguration();
configuration.cassandra.contactPoints = ["localhost"];
configuration.cassandra.keyspace = "tests";

Make sure you defined the TTL - default in config or in every MetaModel. Set undefined if you do not need a TTL

You can use also ENV vars:

$ export CASSANDRA_DBHOST=host1,host2,host3 
$ export CASSANDRA_KEYSPACE=mykeyspace
$ export CASSANDRA_TTL=Number of seconds for default TTL
 

Implement your MetaModel class by extending the MetaModel

If you need to override the default toRow, fromRow function of the MetaModel, you need to extend the MetaModel class.

class FooMetaModel extends MetaModel {
  constructor(jpaConfig)
  {
    super(jpaConfig); 
    this.name = "foo";
    this.fields = new Map([["id", "timeuuid"], ["name", "text"], ["created", "timeuuid"],
        ["entity", "text"], ["entities", "list<text>"], ["simpleObjects", "list<text>"],
        ["enabled", "boolean"]]);
    this.partitionKeys = ["id"];
    this.clusteringColumns = new Map([["name", "ASC"]]);
    this.secondaryIndexes = ["name"];
    this.entityClass = Foo;
    this.ttl = undefined; //no ttl, or X secs, e.g. 86400 for one day
  }
}

See more in the foo example

Building criteriaQuery example

let emFactory = m.Persistence.createEntityManagerFactory("Foo", config);
let entityManager = emFactory.createEntityManager(fooMetaModel);
let cb = entityManager.getCriteriaBuilder();
let cq = cb.createQuery();
let op1 = cb.equal("id", TimeUuid.fromString(foo.id));
let op2 = cb.equal("name", foo.name);
let limit = 1;
let orderBy = "name";
let criteriaQuery = cq.where(cb.and([op1, op2]),limit, orderBy, true);
 
entityManager.findOne(function (error, res)
{
  assert(newFoo instanceof Foo);
  return callback(error, res);
}, criteriaQuery);

See more in the test

Override - extend object model adaptation methods in you MetaModel

This need to be done if the DefaultRowInterceptor does not cover your needs. Alternatively you could extend or replace the DefaultRowInterceptor and maybe also contribute the ideas here.

toRow(entity)
{
 // my specifics
 let row = super.toRow(entity);
  // my specifics
 return row;
}
fromRow(row)
{
 let entity = super.fromRow(row);
 // my specifics
 return entity;
}

See more in the test

When cassandra table should have extra properties comparing to the entity

In our metamodel class, initialize the extra params by giving the param names and an initial value (mostly null).

// add the extra field to the db schema
this.fields.set("newField", "text");
// allow for taking into account when querying
this.extraParams.set("newField", null);

See more in the action

Then when persisting we add the extra params like this:

fooMetaModel.extraParams.set("newField", "some value");

And when we select from db we get of course the entity (missing the extra params) but we can get the extra ones doing:

fooMetaModel.extraParams.get("newField")

See more in the action

API

EntityManger

Function	Arguments	Returns	Description
persist	entity, callback, [metaModel]	callback(error, result)	Persist an entity
persistAll	entities, callback, [metaModel]	callback(error, result)	Persist an arry of entities
updateByCriteria	entity, callback, criteriaQuery, [metaModel]	callback(error, result)	Update Row based on criteriaQuery
removeByCriteria	callback, criteriaQuery, [metaModel]	callback(error, result)	Update Row(s) based on criteriaQuery
findOne	callback, criteriaQuery, [metaModel]	callback(error, result)	Find one entity based on criteriaQuery
findAll	callback, criteriaQuery, [metaModel]	callback(error, result)	Find all entities based on criteriaQuery
query	queryObject, callback	callback(error, result)	general cassandra driver query
truncate	queryObjects, callback	callback(error, result)	Truncate a table based on MetaModel
createTable	callback, [metaModel]	callback(error, result)	Create a table based on MetaModel
insertIndexes	callback, [metaModel]	callback(error, result)	Create indexes based on MetaModel
dropIndexes	callback, [metaModel]	callback(error, result)	Drop indexes based on MetaModel
dropTable	callback, [metaModel]	callback(error, result)	Drop Table based on MetaModel
getCriteriaBuilder	[metaModel]	CriteriaBuilder	get the CriteriaBuilder
getCriteriaQuery	[metaModel]	CriteriaQuery	get the CriteriaQuery

Note: When an EntityManger is initiated using metaModel argument, the [metaModel] can be ommited.

CriteriaBuilder

Function	Arguments	Returns	Description
and	expressions:array	q:string	combine expressions with and AND
equal	x:string, y:ALL	q:string	Tests whether two expressions are equal
gt	x:string, y:ALL	q:string	Tests whether the first numeric expression is greater than the second numeric expression
ge	x:string, y:ALL	q:string	Tests whether the first numeric expression is greater than or equal to the second numeric expression
lt	x:string, y:ALL	q:string	Tests whether the first numeric expression is less than the second numeric expression
le	x:string, y:ALL	q:string	Tests whether the first numeric expression is less than or equal to the second numeric expression

CriteriaQuery

Function	Arguments	Returns	Description
from	q	q:string
where	q, [limit:Number] , [orderBy:String], [allowFiltering:boolean]	q:string

Extending

DefaultRowInterceptor

The DefaultRowInterceptor is the defaul and abstract way that jpa maps the entity field to cassandra rows depending on the field type defined in MetaModel. The following types are supported:

• uuid mapped to require('cassandra-driver').types.TimeUuid
• timeuuid mapped to require('cassandra-driver').types.TimeUuid
• text mapped to JSON.stringnify string
• varchar mapped to JSON.stringnify string
• list mapped to array of JSON.stringnify
• list mapped to array of require('cassandra-driver').types.TimeUuid

The ones not listed are kept as they are, i.e. native support like string, Map etc...

The DefaultRowInterceptor can be extended and overriden.

TODO Features

• Count Results
• Count time

Licence

See license file.