JPA Component

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.

Maven users will need to add the following dependency to their pom.xml for this component:

Sending to the endpoint

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 array of entity beans.

If the body is a List of entities, make sure to use entityType=java.util.ArrayList as a configuration passed to the producer endpoint.

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

From Camel 2.19 onwards you can use query, namedQuery and nativeQuery option for the producer as well to retrieve a set of entities or execute bulk update/delete.

Consuming from the endpoint

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).

If you are consuming a lot (100K+) of rows and experience OutOfMemory problems you should set the maximumResults to sensible value.

Note: Since Camel 2.18, JPA now includes a JpaPollingConsumer implementation that better supports Content Enricher using pollEnrich() to do an on-demand poll that returns either none, one or a list of entities as the result.

URI format

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&...

Options

Message Headers

Camel adds the following message headers to the exchange:

Configuring EntityManagerFactory

Its strongly advised to configure the JPA component to use a specific EntityManagerFactory instance. If failed to do so each JpaEndpoint will auto create their own instance of EntityManagerFactory which most often is not what you want.

For example, you can instantiate a JPA component that references the myEMFactory entity manager factory, as follows:

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.

Configuring TransactionManager

Since Camel 2.3 the JpaComponent will auto lookup the TransactionManager from the Registry. If Camel won't find any TransactionManager instance registered, it will also look up for the TransactionTemplate and try to extract TransactionManager from it.

If none TransactionTemplate is available in the registry, JpaEndpoint will auto create their own instance of TransactionManager which most often is not what you want.

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

Using a consumer with a named query

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:

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

Using a consumer with a query

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

Using a consumer with a native query

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

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

Using a producer with a named query

For retrieving selected entities or execute bulk update/delete, you can use the namedQuery URI query option. First, you have to define the named query in the JPA Entity class:

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

Using a producer with a query

For retrieving selected entities or execute bulk update/delete, you can use the query URI query option. You only have to define the query option:

Using a producer with a native query

For retrieving selected entities or execute bulk update/delete, you can use the nativeQuery URI query option. You only have to define the native query option:

If you use the native query option without specifying resultClass, you will receive an object array in the message body.

Example

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

Using the JPA based idempotent repository

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

First we need to setup a persistence-unit in the persistence.xml file:{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-jpa/src/test/resources/META-INF/persistence.xml}Second we have to setup a org.springframework.orm.jpa.JpaTemplate which is used by the org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository:{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-jpa/src/test/resources/org/apache/camel/processor/jpa/spring.xml}Afterwards we can configure our org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository:{snippet:id=jpaStore|lang=xml|url=camel/trunk/components/camel-jpa/src/test/resources/org/apache/camel/processor/jpa/fileConsumerJpaIdempotentTest-config.xml}And finally we can create our JPA idempotent repository in the spring XML file as well:

Endpoint See Also

• Tracer Example