THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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JPA
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Component
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The
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jpa
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component
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enables
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you
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to
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store
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and
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retrieve
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Java
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objects
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from
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persistent
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storage
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using
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EJB
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3's
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Java
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Persistence
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Architecture
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(JPA),
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which
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is
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a
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standard
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interface
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layer
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that
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wraps
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Object/Relational
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Mapping
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(ORM)
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products
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such
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as
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OpenJPA,
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Hibernate,
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TopLink,
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and
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so
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on.
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Maven
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users
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will
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need
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to
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add
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the
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following
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dependency
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to
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their
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pom.xml
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for
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this
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component:
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{code:xml} <dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-jpa</artifactId> <version>x.x.x</version> <!-- use the same version as your Camel core version --> </dependency> {code} h3. 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|http://java.sun.com/javaee/5/docs/api/javax/persistence/Entity.html] annotation on it) or a collection or array of entity beans. 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. h3. 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|http://camel.apache.org/maven/current/camel-jpa/apidocs/org/apache/camel/component/jpa/Consumed.html] 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|http://camel.apache.org/maven/current/ |
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 does not contain one of the previous listed types, put a Message Translator in front of the endpoint to perform the necessary conversion first.
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).
URI format
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camel-jpa/apidocs/org/apache/camel/component/jpa/PreConsumed.html] which will be invoked on your entity bean before it has been processed (before routing). h3. URI format {code} jpa:entityClassName[?options] {code} |
For
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sending
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to
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the
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endpoint,
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the
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entityClassName
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is
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optional.
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If
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specified,
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it
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helps
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the
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...
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to
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ensure
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the
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body
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is
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of
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the
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correct
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type.
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For
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consuming,
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the
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entityClassName
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is
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mandatory.
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You
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can
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append
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query
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options
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to
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the
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URI
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in
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the
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following
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format,
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?option=value&option=value&...
Options
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}} h3. Options {div:class=confluenceTableSmall} || Name || Default Value || Description || | {{entityType}} | _entityClassName_ | Overrides the _entityClassName_ from the URI. | | {{persistenceUnit}} | {{camel}} | The JPA persistence unit used by default. | | {{consumeDelete}} | {{true}} | *JPA consumer only:* If {{true}}, the entity is deleted after it is consumed; if {{false}}, the entity is not deleted. | | {{consumeLockEntity}} | {{true}} | *JPA consumer only:* Specifies whether or not to set an exclusive lock on each entity bean while processing the results from polling. | | {{flushOnSend}} | {{true}} | *JPA producer only:* Flushes the [EntityManager|http://java.sun.com/javaee/5/docs/api/javax/persistence/EntityManager.html] after the entity bean has been persisted. | | {{maximumResults}} | {{-1}} | *JPA consumer only:* Set the maximum number of results to retrieve on the [Query|http://java.sun.com/javaee/5/docs/api/javax/persistence/Query.html]. | | {{transactionManager}} | {{null}} | This option is [Registry] based which requires the {{#}} notation so that the given {{transactionManager}} being specified can be looked up properly, e.g. {{transactionManager=#myTransactionManager}}. It specifies the transaction manager to use. If none provided, Camel will use a {{JpaTransactionManager}} by default. Can be used to set a JTA transaction manager (for integration with an EJB container). | | {{consumer.delay}} | {{500}} | *JPA consumer only:* Delay in milliseconds between each poll. | | {{consumer.initialDelay}} | {{1000}} | *JPA consumer only:* Milliseconds before polling starts. | | {{consumer.useFixedDelay}} | {{false}} | *JPA consumer only:* Set to {{true}} to use fixed delay between polls, otherwise fixed rate is used. See [ScheduledExecutorService|http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/ScheduledExecutorService.html] in JDK for details. | | {{maxMessagesPerPoll}} | {{0}} | *JPA consumer only:* An integer value to define the maximum number of messages to gather per poll. By default, no maximum is set. Can be used to avoid polling many thousands of messages when starting up the server. Set a value of 0 or negative to disable. | | {{consumer.query}} | | *JPA consumer only:* To use a custom query when consuming data. | | {{consumer.namedQuery}} | | *JPA consumer only:* To use a named query when consuming data. | | {{consumer.nativeQuery}} | | *JPA consumer only:* To use a custom native query when consuming data. You may want to use the option {{consumer.resultClass}} also when using native queries. | | {{consumer.parameters}} | | *Camel 2.12: JPA consumer only:* This option is [Registry] based which requires the {{#}} notation. This key/value mapping is used for building the query parameters. It's is expected to be of the generic type {{java.util.Map<String, Object>}} where the keys are the named parameters of a given JPA query and the values are their corresponding effective values you want to select for. | | {{consumer.resultClass}} | | *Camel 2.7: JPA consumer only:* Defines the type of the returned payload (we will call {{entityManager.createNativeQuery(nativeQuery, resultClass)}} instead of {{entityManager.createNativeQuery(nativeQuery)}}). Without this option, we will return an object array. Only has an affect when using in conjunction with native query when consuming data. | | {{consumer.transacted}} | {{false}} | *Camel 2.7.5/2.8.3/2.9: JPA consumer only:* Whether to run the consumer in transacted mode, by which all messages will either commit or rollback, when the entire batch has been processed. The default behavior (false) is to commit all the previously successfully processed messages, and only rollback the last failed message. | | {{consumer.lockModeType}} | {{WRITE}} | *Camel 2.11.2/2.12:* To configure the lock mode on the consumer. The possible values is defined in the enum {{javax.persistence.LockModeType}}. | | {{usePersist}} | {{false}} | *Camel 2.5: JPA producer only:* Indicates to use {{entityManager.persist(entity)}} instead of {{entityManager.merge(entity)}}. Note: {{entityManager.persist(entity)}} doesn't work for detached entities (where the EntityManager has to execute an UPDATE instead of an INSERT query)! | {div} h3. Message Headers Camel adds the following message headers to the exchange: } |
Message Headers
Camel adds the following message headers to the exchange:
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{div:class=confluenceTableSmall}
|| Header || Type || Description ||
| {{CamelJpaTemplate}} | {{JpaTemplate}} | *Not supported anymore since Camel 2.12:* The {{JpaTemplate}} object that is used to access the entity bean. You need this object in some situations, for instance in a type converter or when you are doing some custom processing. See [CAMEL-5932|https://issues.apache.org/jira/browse/CAMEL-5932] for the reason why the support for this header has been dropped. |
| {{CamelEntityManager}} | {{EntityManager}} | *Camel 2.12: JPA consumer / Camel 2.12.2: JPA producer:* The JPA {{EntityManager}} object being used by {{JpaConsumer}} or {{JpaProducer}}. |
{div}
h3. |
Configuring
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EntityManagerFactory
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Its
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strongly
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advised
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to
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configure
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the
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JPA
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component
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to
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use
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a
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specific
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EntityManagerFactory
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instance.
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If
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failed
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to
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do
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so
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each
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JpaEndpoint
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will
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auto
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create
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their
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own
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instance
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of
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EntityManagerFactory
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which
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most
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often
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is
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not
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what
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you
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want.
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For
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example,
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you
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can
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instantiate
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a
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JPA
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component
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that
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references
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the
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myEMFactory
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entity
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manager
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factory,
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as
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follows:
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{code:xml} <bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent"> <property name="entityManagerFactory" ref="myEMFactory"/> </bean> {code} In *Camel |
In Camel 2.3
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the
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JpaComponent
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will
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auto
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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
Its strongly advised to configure the TransactionManager instance used by the JPA component. If failed to do so each JpaEndpoint will auto create their own instance of TransactionManager which most often is not what you want.
For example, you can instantiate a JPA component that references the myTransactionManager transaction manager, as follows:
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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. h3. Configuring TransactionManager Its strongly advised to configure the {{TransactionManager}} instance used by the JPA component. If failed to do so each {{JpaEndpoint}} will auto create their own instance of {{TransactionManager}} which most often is not what you want. For example, you can instantiate a JPA component that references the {{myTransactionManager}} transaction manager, as follows: {code:xml} <bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent"> <property name="entityManagerFactory" ref="myEMFactory"/> <property name="transactionManager" ref="myTransactionManager"/> </bean> {code} |
In
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Camel
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2.3
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the
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JpaComponent
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will
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auto
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lookup
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the
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TransactionManager
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from
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the
...
...
which
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means
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you
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do
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not
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need
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to
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configure
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this
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on
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the
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JpaComponent
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as
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shown
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above.
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You
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only
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need
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to
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do
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so
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if
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there
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is
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ambiguity,
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in
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which
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case
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Camel
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will
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log
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a
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WARN.
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Using
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a
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consumer
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with
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a
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named
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query
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For
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consuming
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only
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selected
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entities,
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you
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can
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use
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the
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consumer.namedQuery
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URI
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query
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option.
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First,
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you
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have
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to
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define
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the
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named
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query
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in
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the
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JPA
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Entity
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class:
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} @Entity @NamedQuery(name = "step1", query = "select x from MultiSteps x where x.step = 1") public class MultiSteps { ... } {code} |
After
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that
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you
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can
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define
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a
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consumer
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uri
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like
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this
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one:
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} from("jpa://org.apache.camel.examples.MultiSteps?consumer.namedQuery=step1") .to("bean:myBusinessLogic"); |
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:
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{code} h3. 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: {code} 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"); {code} h3. 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 |
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:
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option: {code} from("jpa://org.apache.camel.examples.MultiSteps?consumer.nativeQuery=select * from MultiSteps where step = 1") .to("bean:myBusinessLogic"); {code} |
If
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you
...
use
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the
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native
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query
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option,
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you
...
will
...
receive
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an
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object
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array
...
in
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the
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message
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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:
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h3. Example See [Tracer Example] for an example using [JPA] to store traced messages into a database. h3. 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
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we
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have
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to
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setup
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a
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org.springframework.orm.jpa.JpaTemplate
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which
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is
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used
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by
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the
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org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository:
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}}: {snippet:id=e1|lang=xml|url=camel/trunk/components/camel-jpa/src/test/resources/org/apache/camel/processor/jpa/spring.xml} |
Afterwards
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we
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can
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configure
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our
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org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository:
| Wiki Markup |
|---|
}}: {snippet:id=jpaStore|lang=xml|url=camel/trunk/components/camel-jpa/src/test/resources/org/apache/camel/processor/jpa/fileConsumerJpaIdempotentTest-config.xml} |
And
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finally
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we
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can
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create
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our
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JPA
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idempotent
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repository
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in
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the
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spring
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XML
...
file
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as
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well:
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{code:xml} <camelContext xmlns="http://camel.apache.org/schema/spring"> <route id="JpaMessageIdRepositoryTest"> <from uri="direct:start" /> <idempotentConsumer messageIdRepositoryRef="jpaStore"> <header>messageId</camel:header> <to uri="mock:result" /> </idempotentConsumer> </route> </camelContext> {code} {info:title=When running this Camel component tests inside your IDE} In case you run the [tests of this component|https://svn.apache.org/repos/asf/camel/trunk/components/camel-jpa/src/test] directly inside your IDE (and not necessarily through Maven itself) then you could spot exceptions like: {code:java} |
| Info | ||||||||||||
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In case you run the tests of this component directly inside your IDE (and not necessarily through Maven itself) then you could spot exceptions like:
The problem here is that the source has been compiled/recompiled through your IDE and not through Maven itself which would [enhance the byte-code at build time|https://svn.apache.org/repos/asf/camel/trunk/components/camel-jpa/pom.xml]. To overcome this you would need to enable [dynamic byte-code enhancement of OpenJPA|http://openjpa.apache.org/entity-enhancement.html#dynamic-enhancement]. As an example assuming the current OpenJPA version being used in Camel itself isMaven itself which would enhance the byte-code at build time. To overcome this you would need to enable dynamic byte-code enhancement of OpenJPA. As an example assuming the current OpenJPA version being used in Camel itself is 2.2.1, then as running the tests inside your favorite IDE you would need to pass the following argument to the JVM: {
Then it will all become green again |
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