JavaJPA

Integrating with JPA

First, expose the datasource through JNDI

JPA requires to retrieve the datasource from 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

Add 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 Hibernate dependency to your project:

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

Create 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>

Annotate 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. It will compose your action method with a JPA Action that will manage 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() {
  ...
}

Use 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