Filters vs Interceptors in Struts 2

Question

What\'s the difference, really, between filters and interceptors? I realize that interceptors fire before and after an action, recursively, and filters can be configured to fir

Answer 1

What is Interceptor ?

The Struts 2 Framework uses the concept of Interceptors to share the solution for some common concerns by different actions.

As we know the framework invokes a particular Action object on the submssion of a request for it. But before executing of Action, the invocation is intercepted by some other object to provide additional processing required.

Similarly after the execution of Action, the invocation can be intercepted again. This intercepting object is known as Interceptor.

So the purpose of using Interceptor is to allow greater control over controller layer and separate some common logic that applies to multiple actions.

Struts 2 framework has already provided its own set of Interceptors which can be used in the application to provide required processing before and after the Action classs execution.

One of those is "Alias Interceptor" that I am going to discuss here.

Alias Interceptor:

Alias Interceptor is used in case of Action chaining. Action chaining means one Action calls other Action after successful execution of first action.

This interceptor aliases a named parameter to a different parameter name. In action chaining, when two different action classes share a common parameter with a different name, this Interceptor is used to give an alias name to a parmeter of first action class, which matches the parameter name in the second action class.

The alias expression of action should be in the form of :

             #{ 'name1' : 'alias1' , 'name2' : 'alias2' }