Struts 2 interceptor stack example

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Often times, same set of interceptors may apply to different action classes, for example,

<package name="default" namespace="/" extends="struts-default">    <action name="checkInAction"     class="com.mkyong.common.action.CheckInAction" >    <interceptor-ref name="timer"/>        <interceptor-ref name="logger"/>    <interceptor-ref name="defaultStack" />    <result name="success">pages/checkIn.jsp</result>    </action>    <action name="checkOutAction"     class="com.mkyong.common.action.CheckOutAction" >    <interceptor-ref name="timer"/>        <interceptor-ref name="logger"/>    <interceptor-ref name="defaultStack" />    <result name="success">pages/checkOut.jsp</result>    </action></package>

In above case, it has many duplicated works and not reusable at all.

Fortunately, Struts 2 comes with interceptor stack to allow developer to group a set of interceptors into a single unit called “stack name“, and the actions can reference it via the “stack name“.

Best practice

It’s always recommended to group the same set of interceptors into an interceptor stack to get rid of the duplicated works, and increase the reusebility in your project.

<package name="default" namespace="/" extends="struts-default">     <interceptors>        <interceptor-stack name="defaultStackWithLog">             <interceptor-ref name="timer"/>             <interceptor-ref name="logger"/>         <interceptor-ref name="defaultStack" />        </interceptor-stack>    </interceptors>    <action name="checkInAction"     class="com.mkyong.common.action.CheckInAction" >    <interceptor-ref name="defaultStackWithLog"/>    <result name="success">pages/checkIn.jsp</result>    </action>    <action name="checkOutAction"     class="com.mkyong.common.action.CheckOutAction" >    <interceptor-ref name="defaultStackWithLog"/>    <result name="success">pages/checkOut.jsp</result>    </action></package>

In above updated example, declares an interceptor stack, named “defaultStackWithLog“, which includes the “timer“, “logger” and “defaultStack” interceptors, and reference it as a normal interceptor via “interceptor-ref” element.

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