Struts Controller

ActionServlet

For those of you familiar with MVC architecture, the ActionServlet represents the C - the controller. The job of the controller is to:

• process user requests,
• determine what the user is trying to achieve according to the request,
• pull data from the model (if necessary) to be given to the appropriate view, and
• select the proper view to respond to the user.

Our controller delegates most of this grunt work to the Request Processor and Action classes.

In addition to being the front controller for your application, the ActionServlet instance also is responsible for initialization and clean-up of resources. When the controller initializes, it first loads the application config corresponding to the "config" init-param. It then goes through an enumeration of all init-param elements, looking for those elements who's name starts with config/. For each of these elements, the framework loads the configuration file specified by the value of that init-param, and assigns a "prefix" value to that module's ModuleConfig instance consisting of the piece of the init-param name following "config/". For example, the module prefix specified by the init-param config/foo would be "foo". This is important to know, since this is how the controller determines which module will be given control of processing the request. To access the module foo, you would use a URL like:

http://localhost:8080/myApp/someAction.do

For each request made of the controller, the method process(HttpServletRequest, HttpServletResponse) will be called. This method simply determines which module should service the request and then invokes that module's RequestProcessor's process method, passing the same request and response.