The exception handling mechanism of jBPM only applies to java exceptions. Graph execution on itself cannot result in problems. It is only the execution of delegation classes that can lead to exceptions.

On process-definitions, nodes and transitions, a list of exception-handlers can be specified. Each exception-handler has a list of actions. When an exception occurs in a delegation class, the process element parent hierarchy is serached for an appropriate exception-handler. When it is found, the actions of the exception-handler are executed.

Note that the exception handling mechanism of jBPM is not completely similar to the java exception handling. In java, a caught exception can have an influence on the control flow. In the case of jBPM, control flow cannot be changed by the jBPM exception handling mechanism. The exception is either caught or uncaught. Uncaught exceptions are thrown to the client (e.g. the client that called the token.signal()) or the exception is caught by a jBPM exception-handler. For caught exceptions, the graph execution continues as if no exception has occurred.

Note that in an action that handles an exception, it is possible to put the token in an arbitrary node in the graph with Token.setNode(Node node).