An action class is simply a class which processes a message.

An action can be as simple as a class which prints some of the contents of the message or as complex as one that triggers process flows based upon the message. An action class is activated by the service receiving a message.

As part of a service, actions are generally combined in an action chain, where a single message will be processed by multiple actions. Actions classes usually perform a single atomic action upon a message, but the combination of action classes within an action chain allows services to perform complex tasks and processing of messages.

Action classes are externally configured by properties and settings within the jboss-esb.xml configuration file. The configuration appears within the action class as a ConfigTree object.

An action class usually has initialize and destroy methods, which set up and clean up resources. Additionally there is a process method that performs some sort of stateless action upon the message.