Programming Jakarta Struts

Forward Versus Redirect

It’s often necessary for more than one component to share control of a request. For example, one servlet may be responsible for authenticating and authorizing a client, while it’s the job of a different servlet to retrieve some data for the user. The sharing of a request can be accomplished in several different ways.

There are important differences between how a web container processes a forward request versus how it processes a redirect. The Struts front controller servlet, discussed in Chapter 1, will always perform one or the other for a typical request, so it’s important that you understand these differences and the impact that each mechanism will have on your application.

Using a Redirect

When the sendRedirect( ) method is invoked, it causes the web container to return to the browser a response indicating that a new URL should be requested. Because the browser issues a completely new request, any objects that are stored as request attributes before the redirect occurs will be lost. This is one of the biggest differences between a forward and redirect. Figure 2-5 illustrates why this occurs.

Figure 2-5. A redirect causes the browser to issue a new request

Because of the extra round trip that occurs, a redirect is slower than a forward. Example 2-1 provides an example servlet that performs a redirect for a JSP page called result.jsp when a request for ...