A default routing rule can be either a sequential rule or a parallel rule. A default routing rule, whether sequential or parallel, is guaranteed to be executed when no other routing rule condition is satisfied. When the default rule is executed, the Mediator audit trail shows that the filter conditions of all the routing rules failed, and the filter condition of the default routing rule passed and was executed. The following example provides details:

ActivityJan 7, 2010 4:35:15 PM 
Message onCase "fileout2.Write" 
Jan 7, 2010 4:35:15 PM 
Message Evaluation of xpath condition " No Filter (DEFAULT CASE) " resulted 
true

You can define all routing rules, including default routing rules, as either sequential or parallel routing rules, so the expected behavior of routing rules varies. The following sections discuss each combination and the expected behavior:

Sequential Default Routing Rule

You can have the following possible scenarios with a sequential default routing rule:

• All the other routing rules of the Mediator are sequential: This is the simplest case in which all the routing rules, including the default routing rule, are of a sequential type. Runtime evaluates the filter conditions of all routing rules and, if none of the filter conditions are matched, then the default sequential routing rule is executed. Default sequential routing rule execution happens in the same transaction as the incoming message. After the default rule is executed, a post Java callout occurs.

• At Least One of the Routing Rules of the Mediator are parallel: This is a complex case in which the default routing rule is sequential and at least one of the other routing rules is parallel. The default behavior at runtime is to execute all sequential routing rules first and then execute parallel routing rules. Therefore, this is a tricky situation because a default rule should be executed only after all other routing rules are evaluated to be false.

  In this case, the server first evaluates the filter condition of parallel rules before evaluating the default routing rule filter condition. If none of the other filter conditions are matched, then the default sequential routing rule is executed.

Parallel Default Routing Rule

You can have the following possible scenarios with a parallel default routing rule:

• All the other routing rules of the Mediator are parallel: This is a straightforward case. The default routing rule is not executed if any of the filter conditions specified in the other routing rules are matched. If none of the filter conditions are matched, then the default routing rule is executed asynchronously.

• Other Routing Rules of the Mediator are sequential or parallel: This is a complex but common use case in which there are other sequential or parallel routing rules available, and the default routing rule is parallel. The default routing rule is not executed if any of the other sequential or parallel routing rule criteria is matched. If none of the conditions are matched, then the default routing rule is executed asynchronously.