§Integrating with JPA

§Adding dependencies to your project

First you need to tell play that your project need javaJpa plugin which provide JDBC and JPA api dependencies.

There is no built-in JPA implementation in Play; you can choose any available implementation. For example, to use Hibernate, just add the dependency to your project:
* For Hibernate 4.x:

libraryDependencies ++= Seq(
  javaJpa.exclude("org.hibernate.javax.persistence", "hibernate-jpa-2.0-api"),
  "org.hibernate" % "hibernate-entitymanager" % "4.3.8.Final" // replace by your jpa implementation
)

• For Hibernate 3.6.x:

libraryDependencies ++= Seq(
  javaJpa,
  "org.hibernate" % "hibernate-entitymanager" % "3.6.10.Final" // replace by your jpa implementation
)

§Exposing the datasource through JNDI

JPA requires the datasource to be accessible via JNDI. You can expose any Play-managed datasource via JNDI by adding this configuration in conf/application.conf:

db.default.driver=org.h2.Driver
db.default.url="jdbc:h2:mem:play"
db.default.jndiName=DefaultDS

§Creating a persistence unit

Next you have to create a proper persistence.xml JPA configuration file. Put it into the conf/META-INF directory, so it will be properly added to your classpath.

Here is a sample configuration file to use with Hibernate:

• For Hibernate 4.x:

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"
             version="2.1">

    <persistence-unit name="defaultPersistenceUnit" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <non-jta-data-source>DefaultDS</non-jta-data-source>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
        </properties>
    </persistence-unit>

</persistence>

• For Hibernate 3.6.x:

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
             version="2.0">

    <persistence-unit name="defaultPersistenceUnit" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <non-jta-data-source>DefaultDS</non-jta-data-source>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
        </properties>
    </persistence-unit>

</persistence>

Finally you have to tell Play, which persistent unit should be used by your JPA provider. This is done by the jpa.default property in your application.conf.

jpa.default=defaultPersistenceUnit

§Annotating JPA actions with @Transactional

Every JPA call must be done in a transaction so, to enable JPA for a particular action, annotate it with @play.db.jpa.Transactional. This will compose your action method with a JPA Action that manages the transaction for you:

@Transactional
public static Result index() {
  ...
}

If your action perfoms only queries, you can set the readOnly attribute to true:

@Transactional(readOnly=true)
public static Result index() {
  ...
}

§Using the play.db.jpa.JPA helper

At any time you can retrieve the current entity manager from the play.db.jpa.JPA helper class:

public static Company findById(Long id) {
  return JPA.em().find(Company.class, id);
}

Next: Using the cache