Mule Exception Strategy

1. Mule Exception Strategies
Mule fall into one of two
tupes: System Exceptions,
and Messaging Exceptions.

2. • Mule’s default exception strategy — which
implicitly applies to all Mule applications —
manages errors (such as, thrown exceptions)
in Mule flows.
• Implicitly applied by default to handle all
messaging exceptions that are thrown in Mule
applications

3. System Exceptions
• Mule invokes a System Exception Strategy when an
exception is thrown at the system-level (i.e., when no
message is involved, exceptions are handled by system
exception strategies). For example, system exception
strategies handle exceptions that occur:
• During application at start-up
• connection to an external system fails

4. Catch exception strategy
• Define a catch exception strategy to customize
the way Mule handles any exception. Catch
exception strategies consume inbound
messages, as opposed to rolling them back.

5. • When a system exception occurs, Mule sends
an exception notification to registered
listeners, logs the exception
• When a message being processed through a
Mule flow throws an exception, normal flow
execution stops. Mule transfers the message
to the message processor sequence within the
exception strategy.

6. Rollback exception strategy
• Define a rollback exception strategy to ensure
that a message that throws an exception in a
flow is rolled back for reprocessing (if the
message source supports redelivery). Rollback
exception strategies do not consume inbound
messages.

7. Reference exception strategy
• Define a reference exception strategy to refer
and adhere to the error handling parameters
defined in a global catch, rollback or choice
exception strategy.

8. Choice exception strategy
• Define a choice exception strategy to
customize the way Mule handles a message
that throws an exception based on the
message’s content at the moment it throws
the exception.

9. Characteristics of Messaging Exception Strategies
• Each flow can contain only one exception strategy.
• Each exception strategy can contain any number of message processors.
• Choice exception strategies can contain one or more catch and/or rollback
exception strategies. (Rollback and catch exception strategies cannot,
however, contain other exception strategies.)
• You can create one or more global exception strategies to reuse in flows
throughout your entire Mule application.
• A Transactional Scope may include its own exception strategy, regardless
of what you define at Flow level