Chapter 2. Getting started with transactions on Karaf (OSGi)

Implementation of this Camel application has the following prerequisites:

You can download the quickstarts from the Fuse Software Downloads page.

Extract the contents of the zip file to a local folder, for example a new folder named quickstarts.

You can then build and install the /camel/camel-jms example as an OSGi bundle. This bundle contains a Blueprint XML definition of a Camel route that sends messages to an AMQ 7 JMS queue.

In the following example, $FUSE_HOME is the location of the unzipped Fuse distribution. To build this project:

Camel routes are using the following endpoint URIs:

<route id="file-to-jms-route">
...
    <to uri="jms:queue:incomingOrders?transacted=true" />
</route>

<route id="jms-cbr-route">
    <from uri="jms:queue:incomingOrders?transacted=true" />
...
</route>

The jms component is configured by using this snippet:

<bean id="jms" class="org.apache.camel.component.jms.JmsComponent">
    <property name="connectionFactory">
        <reference interface="javax.jms.ConnectionFactory" />
    </property>
    <property name="transactionManager" ref="transactionManager"/>
</bean>

While the transactionManager reference is:

<reference id="transactionManager" interface="org.springframework.transaction.PlatformTransactionManager" />

As you can see, both the JMS connection factory and the Spring interface of PlatformTransactionManager are only references. There is no need to define them in Blueprint XML. These services are exposed by Fuse itself.

You have already seen that javax.jms.ConnectionFactory was created by using etc/org.ops4j.connectionfactory-amq7.cfg.

The transaction manager is:

karaf@root()> service:list org.springframework.transaction.PlatformTransactionManager
[org.springframework.transaction.PlatformTransactionManager]
------------------------------------------------------------
 service.bundleid = 21
 service.id = 527
 service.scope = singleton
Provided by :
 Red Hat Fuse :: Fuse Modules :: Transaction (21)
Used by:
 Red Hat Fuse :: Quickstarts :: camel-jms (256)

Check for other interfaces under which the actual transaction manager is registered:

karaf@root()> headers 21

Red Hat Fuse :: Fuse Modules :: Transaction (21)
------------------------------------------------
...
Bundle-Name = Red Hat Fuse :: Fuse Modules :: Transaction
Bundle-SymbolicName = fuse-pax-transx-tm-narayana
Bundle-Vendor = Red Hat
...

karaf@root()> bundle:services -p 21

Red Hat Fuse :: Fuse Modules :: Transaction (21) provides:
----------------------------------------------------------
objectClass = [org.osgi.service.cm.ManagedService]
service.bundleid = 21
service.id = 519
service.pid = org.ops4j.pax.transx.tm.narayana
service.scope = singleton
 ----
objectClass = [javax.transaction.TransactionManager]
provider = narayana
service.bundleid = 21
service.id = 520
service.scope = singleton
 ----
objectClass = [javax.transaction.TransactionSynchronizationRegistry]
provider = narayana
service.bundleid = 21
service.id = 523
service.scope = singleton
 ----
objectClass = [javax.transaction.UserTransaction]
provider = narayana
service.bundleid = 21
service.id = 524
service.scope = singleton
 ----
objectClass = [org.jboss.narayana.osgi.jta.ObjStoreBrowserService]
provider = narayana
service.bundleid = 21
service.id = 525
service.scope = singleton
 ----
objectClass = [org.ops4j.pax.transx.tm.TransactionManager]
provider = narayana
service.bundleid = 21
service.id = 526
service.scope = singleton
 ----
objectClass = [org.springframework.transaction.PlatformTransactionManager]
service.bundleid = 21
service.id = 527
service.scope = singleton

The transaction manager is available from these interfaces:

You can use any of them in any context that you need. For example camel-jms requires that the org.apache.camel.component.jms.JmsConfiguration.transactionManager field be initialized. This is why the example uses:

<reference id="transactionManager" interface="org.springframework.transaction.PlatformTransactionManager" />

instead of, for example:

<reference id="transactionManager" interface="javax.transaction.TransactionManager" />