Configuring the persistence.xml File

The persistence.xml file is the deployment descriptor file for persistence using JPA. It specifies the persistence units and declares the managed persistence classes, the object/relation mapping, and the database connection details.

Main Tasks

To configure the persistence.xml file, the following tasks:

Task 1: Use the persistence.xml File
Task 2: Instantiate EntityManagerFactory

Task 1: Use the persistence.xml File

Example 17-2 illustrates a persistence.xml file for a Java SE platform configuration (that is, outside a container).

Example 17-2 A persistence.xml File Specifying the Java SE Platform Configuration

<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 persistence_1_0.xsd" version="1.0">
    <persistence-unit name="my-app" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <exclude-unlisted-classes>false</exclude-unlisted-classes>
        <properties>
            <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>
            <property name="javax.persistence.jdbc.user" value="scott"/>
            <property name="javax.persistence.jdbc.password" value="tiger"/>
        </properties>
    </persistence-unit>
</persistence>

Task 2: Instantiate EntityManagerFactory

An EntityManagerFactory provides an efficient way to construct EntityManager instances for a database. You can instantiate the EntityManagerFactory for the application (illustrated in Example 17-2) by using:

Persistence.createEntityManagerFactory("my-app");