JPA

The jpa component enables you to store and retrieve Java objects from persistent storage using EJB 3's Java Persistence Architecture (JPA), which is a standard interface layer that wraps Object/Relational Mapping (ORM) products such as OpenJPA, Hibernate, TopLink, and so on.

You can store a Java entity bean in a database by sending it to a JPA producer endpoint. The body of the In message is assumed to be an entity bean (that is, a POJO with an @Entity annotation on it) or a collection or an array of entity beans.

If the body does not contain one of the preceding types, put a Message TranslatorMessage Translator in front of the endpoint to perform the necessary conversion first.

Consuming messages from a JPA consumer endpoint removes (or updates) entity beans in the database. This allows you to use a database table as a logical queue: consumers take messages from the queue and then delete/update them to logically remove them from the queue.

If you do not wish to delete the entity bean when it has been processed (and when routing is done), you can specify consumeDelete=false on the URI. This will result in the entity being processed each poll.

If you would rather perform some update on the entity to mark it as processed (such as to exclude it from a future query) then you can annotate a method with @Consumed which will be invoked on your entity bean when the entity bean when it has been processed (and when routing is done).

From Camel 2.13 onwards you can use @PreConsumed which will be invoked on your entity bean before it has been processed (before routing).

jpa:entityClassName[?options]

For sending to the endpoint, the entityClassName is optional. If specified, it helps the Type Converter to ensure the body is of the correct type.

For consuming, the entityClassName is mandatory.

You can append query options to the URI in the following format, ?option=value&option=value&...

Apache Camel adds the following message headers to the exchange:

You are strongly advised to configure the JPA component to use a specific EntityManagerFactory instance. If you do not do so, each JpaEndpoint will auto-create its own EntityManagerFactory instance.For example, you can instantiate a JPA component that references the myEMFactory entity manager factory, as follows:

<bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent">
   <property name="entityManagerFactory" ref="myEMFactory"/>
</bean>

In Camel 2.3 the JpaComponent will auto lookup the EntityManagerFactory from the Registry which means you do not need to configure this on the JpaComponent as shown above. You only need to do so if there is ambiguity, in which case Camel will log a WARN.

Since Camel 2.3 the JpaComponent will auto lookup the TransactionManager from the Registry. If Camel does not find any TransactionManager instance registered, it will also look up for the TransactionTemplate and try to extract TransactionManager from it. If no TransactionTemplate is available in the registry, JpaEndpoint will auto-create its own instance of TransactionManager.

If more than a single instance of the TransactionManager is found, Camel logs a WARN message. In such cases, you might want to instantiate and explicitly configure a JPA component that references the myTransactionManager transaction manager, as follows:

<bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent">
   <property name="entityManagerFactory" ref="myEMFactory"/>
   <property name="transactionManager" ref="myTransactionManager"/>
</bean>

For consuming only selected entities, you can use the consumer.namedQuery URI query option. First, you have to define the named query in the JPA Entity class:

@Entity
@NamedQuery(name = "step1", query = "select x from MultiSteps x where x.step = 1")
public class MultiSteps {
   ...
}

After that you can define a consumer uri like this one:

from("jpa://org.apache.camel.examples.MultiSteps?consumer.namedQuery=step1")
.to("bean:myBusinessLogic");

For consuming only selected entities, you can use the consumer.query URI query option. You only have to define the query option:

from("jpa://org.apache.camel.examples.MultiSteps?consumer.query=select o from org.apache.camel.examples.MultiSteps o where o.step = 1")
.to("bean:myBusinessLogic");

For consuming only selected entities, you can use the consumer.nativeQuery URI query option. You only have to define the native query option:

from("jpa://org.apache.camel.examples.MultiSteps?consumer.nativeQuery=select * from MultiSteps where step = 1")
.to("bean:myBusinessLogic");

If you use the native query option, you will receive an object array in the message body.

See the Tracer Example for an example using JPA to store traced messages into a database.

In this section we will use the JPA based idempotent repository.

First we need to setup a persistence-unit in the persistence.xml file:

<persistence-unit name="idempotentDb" transaction-type="RESOURCE_LOCAL">
   <class>org.apache.camel.processor.idempotent.jpa.MessageProcessed</class>
 
   <properties>
     <property name="openjpa.ConnectionURL" value="jdbc:derby:target/idempotentTest;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"/>
   </properties>
 </persistence-unit>

Second we have to setup a org.springframework.orm.jpa.JpaTemplate which is used by the org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository:

<!-- this is standard spring JPA configuration -->
 <bean id="jpaTemplate" class="org.springframework.orm.jpa.JpaTemplate">
     <property name="entityManagerFactory" ref="entityManagerFactory"/>
 </bean>
 
 <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
     <!-- we use idempotentDB as the persitence unit name defined in the persistence.xml file -->
     <property name="persistenceUnitName" value="idempotentDb"/>
 </bean>

Afterwards we can configure our org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository:

<!-- we define our jpa based idempotent repository we want to use in the file consumer -->
 <bean id="jpaStore" class="org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository">
     <!-- Here we refer to the spring jpaTemplate -->
     <constructor-arg index="0" ref="jpaTemplate"/>
     <!-- This 2nd parameter is the name  (= a cateogry name).
          You can have different repositories with different names -->
     <constructor-arg index="1" value="FileConsumer"/>
 </bean>

And finally we can create our JPA idempotent repository in the spring XML file as well:

<camelContext xmlns="http://camel.apache.org/schema/spring">	
    <route id="JpaMessageIdRepositoryTest">
        <from uri="direct:start" />
        <idempotentConsumer messageIdRepositoryRef="jpaStore">
            <header>messageId</header>
            <to uri="mock:result" />
        </idempotentConsumer>
    </route>
</camelContext>