Revision as of 10:51, 15 June 2010

persistence.xml

A persistence unit configures various details that are required when you acquire an entity manager. You specify a persistence unit by name when you acquire an entity manager factory.

You configure persistence units in the JPA persistence descriptor file: persistence.xml. This file should be in the meta-inf/ directory of your persistence unit jar file, or classpath.

In this file, you can specify the vendor extensions that this reference describes by using a <properties> element.

<persistence-unit name="default" transaction-type="RESOURCE_LOCAL">
  <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
 
  <!-- By default your mappings can be defined in orm.xml file, -->
  <!-- which is discovered automatically.                       -->                                     
  <mapping-file>META-INF/my-mappings.xml</mapping-file>
  ...
  <jar-file>my-additional-jar.jar</jar-file>
  ...
  <!-- Enables auto discovery of persistent classes, -->
  <!-- otherwise they must be listed using <class>  -->
  <exclude-unlisted-classes>false</exclude-unlisted-classes>
 
  <properties>
    ...
  </properties>
</persistence-unit>

How to Specify the Persistence Unit Name

If you are developing your application in a Java EE environment, ensure that the persistence unit name is unique within each module. For example, you can define only one persistence unit with the name "EmployeeService" in an emp_ejb.jar file. The following example shows how to define the name of the persistence unit:

<persistence-unit name="EmployeeService">

For more information, see Section 6.2.1.1 "name" of the JPA Specification.

JPA	Configuration	Annotations
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