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Introduction

So far our tutorials have not delved into the inner workings of the Struts 2 framework. But in this tutorial we'll introduce a key set of classes the Struts 2 framework relies upon to do most of the work whenever an Action is executed. In this tutorial's example project there is a register link that is mapped in the Struts XML configuration file (struts.xml) to the execute method of class Register. Before that execute method is called much work is done behind the scenes by the Struts 2 framework. For example:

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Sometime the Struts 2 default stack of interceptors are not exactly what you need for a particular action. You may want to use interceptors that are not part of the Struts 2 default stack. For an individual Action or for the entire package of Actions, you can specify a different stack of interceptors that the Action or package should use. Below is how you would specify that the register Action should use both the logger and timer interceptors in addition to the interceptors provided by the default stack.

<action name="register" class="org.apache.struts.register.action.Register" method="execute">
	<interceptor-ref name="timer" />
	<interceptor-ref name="logger" />
	<interceptor-ref name="defaultStack">
		<param name="exception.logEnabled">true</param>
		<param name="exception.logLevel">ERROR</param>
	</interceptor-ref>
	<result name="success">thankyou.jsp</result>
	<result name="input">register.jsp</result>
</action>

The logger interceptor logs the start and end of the execution of an Action. The timer interceptor logs the amount of time (in milliseconds) for execution of the Action. These two interceptors used together can provide developers useful feedback.

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Note the param nodes. These nodes are used to provide a value to the setLogEnabled and setLogLevel methods of the exception interceptor Exception Interceptor. Providing the values of true and ERROR will cause the Struts 2 framework to log any exceptions not caught by the application's code and to log those exceptions at the ERROR level.

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Nov 20, 2010 9:55:48 AM com.opensymphony.xwork2.util.logging.jdk.JdkLogger info

INFO: Executed action //register!execute took 177 ms.

If you wanted to have the logger and timer interceptors executed for all Actions in a package you would use the following in struts.xml:

<package name="basicstruts2" extends="struts-default" > 


       <interceptors> 

         <interceptor-stack name="appDefault"> 

            <interceptor-ref name="timer" /> 

            <interceptor-ref name="logger" /> 

            <interceptor-ref name="defaultStack" /> 

         </interceptor-stack> 

        </interceptors> 

         

        <default-interceptor-ref name="appDefault" /> 

       <!-- rest of package omitted --> 


</package> 

In the code above we use the interceptors node to define a new stack of interceptors that includes the timer, logger, and defaultStack interceptors. We give this new interceptor stack a name of appDefault. Then we use the default-interceptor-ref node to specify that for all Actions defined inside this package node the appDefault stack of interceptors are to be used. Thus the timer and logger interceptor will be executed for each Action in this package.

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