What are Interceptor Stacks in Struts 2x ?

Interceptors can be grouped into named Interceptor Stacks.

Several stacks come pre-defined in struts-default.xml

Example (defaultStack)

<interceptor-stack name="defaultStack">

   <interceptor-ref name="static-params"/>

   <interceptor-ref name="params"/>

   <interceptor-ref name="conversionError"/>

</interceptor-stack>

Example (validationWorkflowStack including defaultStack)

<interceptor-stack name="validationWorkflowStack">

   <interceptor-ref name="defaultStack"/>

   <interceptor-ref name="validation"/>

   <interceptor-ref name="workflow"/>

</interceptor-stack>

Stacks can be built of other stacks and interceptors.