§Integrating with JPA

§Exposing the datasource through JNDI

JPA requires the datasource to be accessible via JNDI. You can expose any Play-managed datasource via JDNI 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

§Adding a JPA implementation to your project

There is no built-in JPA implementation in Play 2.0; you can choose any available implementation. For example, to use Hibernate, just add the dependency to your project:

val appDependencies = Seq(
  "org.hibernate" % "hibernate-entitymanager" % "3.6.9.Final"
)

§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:

<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>

§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