How to Configure Exception Handling in Mule

An exception is a difficulty that arises during the implementation of a program. An exception can occur for many different reasons, including the following :

• A user has entered invalid data.

• A file that needs to be opened cannot be found.

• A network connection has been lost in the middle of communications or the JVM has run out of memory.

Some of these exceptions are caused by user error, others by programmer error, and others by physical resources that have failed in some manner. There are different type of exception in Mule.

 

1. Default Connector Exception Strategy

 

Let us say for example we have a file inbound and the data are send as form of mail.

So <default-connector-exception-strategy/> automatically takes care of the exception that is taking care of it.

 

2. Default Service Exception Strategy

 

It throws exception for all Services on behalf of it.

<model name="randomGeneratorModel">
<default-service-exception-strategy/>
<service name="RandomIntegerGenerator">
<inbound>
<vm:inbound-endpoint path="RIG.In" />
</inbound>
<component>
<no-arguments-entry-point-resolver>
<include-entry-point method="nextInt"/>
</no-arguments-entry-point-resolver>
<singleton-object class="java.util.Random" />
</component>
</service>
..
</model>

 

3. Sending all service level exceptions to JMS queue

 

Here is the following example for exception handling

Not always we send all excpetions to get handled internally in some cases we may need our own logic to handle exceptions.

For (ex)
<model name="randomGeneratorModel">
<default-connector-exception-strategy>
<jms:outbound-endpoint queue="transport-errors"/>
</default-connector-exception-strategy>
<default-service-exception-strategy>
<jms:outbound-endpoint queue="business-errors"/>
</default-service-exception-strategy>
<service name="RandomIntegerGenerator">
<inbound>
<vm:inbound-endpoint path="RIG.In" />
</inbound>
<component>
<no-arguments-entry-point-resolver>
<include-entry-point method="nextInt"/>
</no-arguments-entry-point-resolver>
<singleton-object class="java.util.Random" />
</component>
</service>

 

4.Rollback Strategy Exception Handling

 

In this type of strategy, failure may cause at any point of time and you need to re-execute  the use case for the defined number of times it may be 1, 2, …, n.

Consider we are having a case in which  we are not able to connect to server now we want to perform this action for 5 times and if we do not get succeeded in those attempts then we will try to get connected to another server.

So for Looped execution we will write

       <rollback-exception-strategy maxRedeliveryAttempts="3">
    and for maximum exceeded attempts we need to execute     
        <on-redelivery-attempts-exceeded>
For ex.
<jms:activemq-connector name="activeMQ"/>
<flow>
   <jms:inbound-endpoint queue="in">
      <jms:transaction action="ALWAYS_BEGIN"/>
   </jms:inbound-endpoint>
   <processor ref="processor"/>
   <rollback-exception-strategy maxRedeliveryAttempts="3">
      <on-redelivery-attempts-exceeded>
         <jms:outbound-endpoint queue="dlq">
            <jms:transaction action="ALWAYS_JOIN"/> 
         </jms:outbound-endpoint>
      </on-redelivery-attempts-exceeded>
   </rollback-exception-strategy>
</flow>

http://www.mulesoft.org/documentation/display/current/Rollback+Exception+Strategy+Behavior

http://www.mulesoft.org/documentation/display/current/Rollback+Exception+Strategy+Documentation