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Transaction Oriented Endpoints (Camel Toes) like JMS support using a transaction for both inbound and outbound message exchanges. Endpoints that support transactions will participate in the current transaction context that they are called from.

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<route>
  <from uri="activemq:queue:foo"/>
  <transacted ref="required"/>
  <to uri="activemq:queue:bar"/>
</route>

Camel 1.x - Database Sample

In this sample we want to ensure that two endpoints is under transaction control. These two endpoints inserts data into a database.
The sample is in its full as a unit test.

First of all we setup the usual spring stuff in its configuration file. Here we have defined a DataSource to the HSQLDB and a most importantly
the Spring DataSoruce TransactionManager that is doing the heavy lifting of ensuring our transactional policies. You are of course free to use any
of the Spring based TransactionMananger, eg. if you are in a full blown J2EE container you could use JTA or the WebLogic or WebSphere specific managers.

We use the required transaction policy that we define as the PROPOGATION_REQUIRED spring bean. And as last we have our book service bean that does the business logic
and inserts data in the database as our core business logic.

{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/interceptor/transactionalClientDataSource.xml}

In our Camel route that is Java DSL based we setup the transactional policy, wrapped as a Policy.

{snippet:id=e1|lang=java|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/interceptor/TransactionalClientDataSourceTest.java}

Then we are ready to define our Camel routes. We have two routes: 1 for success conditions, and 1 for a forced rollback condition.
This is after all based on a unit test.

{snippet:id=e2|lang=java|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/interceptor/TransactionalClientDataSourceTest.java}

As its a unit test we need to setup the database and this is easily done with Spring JdbcTemplate

{snippet:id=e5|lang=java|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/interceptor/TransactionClientDataSourceSupport.java}

And our core business service, the book service, will accept any books except the Donkeys.

{snippet:id=e1|lang=java|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/interceptor/BookService.java}

Then we are ready to fire the tests. First to commit condition:

{snippet:id=e3|lang=java|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/interceptor/TransactionalClientDataSourceTest.java}

And lastly the rollback condition since the 2nd book is a Donkey book:

{snippet:id=e4|lang=java|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/interceptor/TransactionalClientDataSourceTest.java}

Camel 1.x - JMS Sample

In this sample we want to listen for messages on a queue and process the messages with our business logic java code and send them along. Since its based on a unit test the destination is a mock endpoint.

This time we want to setup the camel context and routes using the Spring XML syntax.

{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-jms/src/test/resources/org/apache/camel/component/jms/tx/JMSTransactionalClientTest.xml}

Since the rest is standard XML stuff its nothing fancy now for the reader:

{snippet:id=e2|lang=xml|url=camel/trunk/components/camel-jms/src/test/resources/org/apache/camel/component/jms/tx/JMSTransactionalClientTest.xml}

Our business logic is set to handle the incomming messages and fail the first two times. When its a success it responds with a Bye World message.

{snippet:id=e2|lang=java|url=camel/trunk/components/camel-jms/src/test/java/org/apache/camel/component/jms/tx/JMSTransactionalClientTest.java}

And our unit test is tested with this java code. Notice that we expect the Bye World message to be delivered at the 3rd attempt.

{snippet:id=e1|lang=java|url=camel/trunk/components/camel-jms/src/test/java/org/apache/camel/component/jms/tx/JMSTransactionalClientTest.java}

Camel 1.x - Spring based configuration

In Camel 1.4 we have introduced the concept of configuration of the error handlers using spring XML configuration. The sample below demonstrates that you can configure transaction error handlers in Spring XML as spring beans. These can then be set as global, per route based or per policy based error handler. The latter has been demonstrated in the samples above. This sample is the database sample configured in Spring XML.

Notice that we have defined two error handler, one per route. The first route uses the transaction error handler, and the 2nd uses no error handler at all.

{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-jms/src/test/resources/org/apache/camel/component/jms/tx/TransactionErrorHandlerBuilderAsSpringBeanTest.xml}

The following snippet is the Spring XML configuration to setup the error handlers in pure spring XML:

{snippet:id=e2|lang=xml|url=camel/trunk/components/camel-jms/src/test/resources/org/apache/camel/component/jms/tx/TransactionErrorHandlerBuilderAsSpringBeanTest.xml}

DelayPolicy (@deprecated)

DelayPolicy is a new policy introduced in Camel 1.5, to replaces the RedeliveryPolicy used in Camel 1.4. Notice the transactionErrorHandler can be configured with a DelayPolicy to set a fixed delay in millis between each redelivery attempt. Camel does this by sleeping the delay until transaction is marked for rollback and the caused exception is rethrown.

This allows a simple redelivery interval that can be configured for development mode or light production to avoid a rapid redelivery strategy that can exhaust a system that constantly fails.

The DelayPolicy is @deprecated and removed in Camel 2.0. All redelivery configuration should be configured on the back system.

We strongly recommend that you configure the backing system for correct redelivery policy in your environment.

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Database Sample

In this sample we want to ensure that two endpoints is under transaction control. These two endpoints inserts data into a database.
The sample is in its full as a unit test.

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That is all that is needed to configure a Camel route as being transacted. Just remember to use the transacted DSL. The rest is standard Spring XML to setup the transaction manager.

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JMS Sample

In this sample we want to listen for messages on a queue and process the messages with our business logic java code and send them along. Since its based on a unit test the destination is a mock endpoint.

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