Creating Custom (Own) Request Processor in Struts 1.x

Struts 1.x framework can be extended in many  ways. One of the way is creating custom (own) request processor. Why we need to create custom request processor?. There may common tasks to be done on every request. For example 1) to check an user is logged in by checking the userName attribute in the session  before executing every request (i.e Validating user Session) 2) Checking roles of a user whether the particular user has rights to access the particular action method 3) capturing user activities in log table, etc..

Processing of a Request:

ActionServlet is the only servlet in Struts framework which is responsible for handling all of the requests. Whenever it receives a request, it creates a object of the RequestProcessor class ( i.e before redirecting to the programmer’s action, ActionServlet creates an object of RequestProcessor) and calls its process() method by passing HttpServletRequest and HttpServletResponse objects. The RequestProcessor class in the Struts has many methods like process(),processPreprocess(),processContent(). You can override any of the methods to do any common activities for each request.

For example, default implementation of process() method is as follows.

You have to do two things to implement custom request processor in struts.

1. Add the following lines to your struts-config.xml file after the element <action-mappings>   …. </action-mappings> to inform Struts that OwnRequestProcessor should be used as the RequestProcessor class.

<controller>
         <set-property property="processorClass" value="util.OwnRequestProcessor " />
</controller>

2. Create a class for example OwnRequestProcessor extending class RequestProcessor and override the method processPreprocess for example. The processPreprocess always return true. Returning false from this method will abort request processing. For example if user is not valid for the requested action then you may return false.

Before going to the implementation, let us see the sequence of processing a request in struts. Suppose user is requesting the action UserAction.

user request -> ActionServlet -> RequestProcessor -> if processPreprocess return true -> UserAction

Now let us  override processPreprocess method of RequestProcessor in OwnRequestProcessor for controlling  user access. Create your own OwnCustomRequestProcessor class under util package, which will extend the RequestProcessor class as given below.

 

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