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In Example 2.4, the jpaTxManager bean is a local JPA transaction manager instance, of JpaTransactionManager type. The JPA transaction manager requires a reference to an entity manager factory bean (in this example, the entityManagerFactory bean).

If you deploy your application into an OSGi container, however, you might want to consider using a JtaTransactionManager instead. See Table 2.2.

Example 2.5 shows a sample persistence.xml file for configuring an OpenJPA JPA provider layered over a Derby database.

Example 2.5. Sample persistence.xml File

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns=""

  <persistence-unit name="camel" transaction-type="RESOURCE_LOCAL">
        The default provider can be OpenJPA, or some other product.
        This element is optional if OpenJPA is the only JPA provider
        in the current classloading environment, but can be specified
        in cases where there are multiple JPA implementations available.
    <provider> 1

    <class>org.apache.camel.examples.MultiSteps</class> 2

    <properties> 3
      <property name="openjpa.ConnectionURL" value="jdbc:derby:target/derby;create=true"/>
      <property name="openjpa.ConnectionDriverName" value="org.apache.derby.jdbc.EmbeddedDriver"/>
      <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema"/>
      <property name="openjpa.Log" value="DefaultLevel=WARN, Tool=INFO, SQL=TRACE"/>



The provider element can be used to specify the OpenJPA provider implementation class. If the provider element is omitted, the JPA layer simply uses the first JPA provider it can find. Hence, it is recommended to specify the provider element, if there are multiple JPA providers on your class path.

To make a JPA provider available to an application, simply add the provider's JAR file to the class path and the JPA layer will auto-detect the JPA provider.


Use the class elements to list all of the Java types that you want to persist using the JPA framework.


Use the properties element to configure the underlying JPA provider. In particular, you should at least provide enough information here to configure the connection to the underlying database.

The following code example shows how the org.apache.camel.examples.SendEmail class referenced in Example 2.5 should be annotated to turn it into a persistent entity bean (so that it is persistible by JPA):

// Java
package org.apache.camel.examples;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

 * Represents a task which is added to the database, then removed from the database when it is consumed
 * @version $Revision$
public class SendEmail {
    private Long id;
    private String address;

    public SendEmail() {

    public SendEmail(String address) {

    public String toString() {
        return "SendEmail[id: " + getId() + " address: " + getAddress() + "]";

    public Long getId() {
        return id;

    public void setId(Long id) { = id;

    public String getAddress() {
        return address;

    public void setAddress(String address) {
        this.address = address;

The preceding class has the following JPA annotations:


Specifies that the following class is persistible by the JPA.


The following bean property must be used as the primary key (for locating objects of this type in the database).


Specifies that the primary key values should be automatically generated by the JPA runtime (you can optionally set attributes on this annotation to configure the ID generation algorithm as well).

For the complete list of JPA annotations, see the API for the javax.persistence package.

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