Using Interceptors
Mule ESB interceptors are useful for attaching behaviors to multiple components. The interceptor pattern is often referred to as practical AOP (Aspect Oriented Programming), as it allows the developer to intercept processing on an object and potentially alter the processing and outcome. (See also Spring AOP). Interceptors are very useful for attaching behavior such as profiling and permission and security checks to your components.
is an envelope filter that will execute before and after the component is invoked. Good for logging and profiling.
Writing Interceptors
If you want to intercept a message flow to a component on the inbound message flow, you should implement the Interceptor interface. It has a single method:
MuleEvent process(MuleEvent event);The event parameter contains the current message. Developers can extract the current MuleMessage from the message and manipulate it as needed. The process method must return a MuleMessage that will be passed on to the component (or to the next interceptor in the chain).
The AbstractEnvelopeInterceptor is an envelope filter that executes before and after the component is invoked. Good for logging and profiling. works in the same way, except that it exposes two methods that get invoked before and after the event processing:
MuleEvent before(MuleEvent event) throws MuleException;
MuleEvent after(MuleEvent event) throws MuleException;Configuring Interceptors
Interceptors can be configured on your components as follows:
<flow name="MyService">
<custom-interceptor class="org.my.CustomInterceptor"/>
<logging-interceptor/>
<interceptor-stack ref="testInterceptorStack"/>
<timer-interceptor/>
<prototype-object class="org.my.ComponentImpl"/>
</flow>
When you configure interceptors, you must specify the object factory explicitly (in this example, <prototype-object>) instead of using the <component class> shortcut.
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You can also define interceptor stacks, which are one or more interceptors that can be referenced using a logical name. To use an interceptor stack, you must first configure it in the global section of the Mule XML configuration file (above the <model> element):
<interceptor-stack name="default">
<custom-interceptor class="org.my.CustomInterceptor"/>
<logging-interceptor/>
</interceptor-stack>You can configure multiple <interceptor> elements on your components, and you can mix using built-in interceptors, custom interceptors, and references to interceptor stacks.