9.3. Demarcation by UserTransaction

Overview

It is possible to demarcate a transaction by accessing the UserTransaction service directly and calling its begin(), commit() and rollback() methods. But you should be careful to call these methods only when it is really necessary. Usually, in a Apache Camel application, a transaction would be started either by a transactional endpoint or by the transacted() marker in a route, so that explicit invocations of UserTransaction methods are not required.

Accessing UserTransaction from Apache Camel

In the case of Apache Camel applications deployed in an OSGi container, you can easily obtain a reference to the UserTransaction OSGi service by looking it up in the CamelContext registry. For example, given the CamelContext instance, camelContext, you could obtain a UserTransaction reference as follows: 
// Java
import javax.transaction.UserTransaction;
...
UserTransaction ut =
    (UserTransaction) camelContext.getRegistry().lookup(UserTransaction.class.getName());
For more details of how the registry is integrated with OSGi, see Integration with Apache Camel.

Example with UserTransaction

The following example shows how to access a UserTransaction object and use it to demarcate a transaction, where it is assumed that this code is part of a Apache Camel application deployed inside an OSGi container. 
// Java
import javax.transaction.UserTransaction;
...
UserTransaction ut =
    (UserTransaction) camelContext.getRegistry().lookup(UserTransaction.class.getName());

try {
  ut.begin();
  ...
  // invoke transactional methods or endpoints
  ...
  ut.commit();
}
catch (Exception e) {
  ut.rollback();
}