Programming Jakarta Struts, Second Edition

Struts Controller Components

The controller component in an MVC application has several responsibilities, including receiving input from a client, invoking a business operation, and coordinating the view to return to the client. Of course, the controller may perform many other functions, but these are a few of the primary ones.

For an application built using the JSP Model 2 approach, the controller is implemented by a Java servlet. This servlet is the centralized point of control for the web application. The controller servlet maps user actions into business operations and then helps to select the view to return to the client based on the request and other state information. As a reminder, Figure 3-5 shows the figure used in Chapter 1 to illustrate how this works.

Figure 3-5. The Struts framework uses a servlet as a controller

In the Struts framework, however, the controller responsibilities are implemented by several different components, one of which is an instance of the org.apache.struts.action.ActionServlet class.

The Struts ActionServlet

The ActionServlet extends the javax.servlet.http.HttpServlet class and is responsible for packaging and routing HTTP traffic to the appropriate handler in the framework. The ActionServlet class is not abstract and therefore can be used as a concrete controller by your applications. Prior to Version 1.1 of the Struts framework, the ActionServlet ...