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Development Standards in Apache Struts
by Keld H. Hansen
Apache Struts is a great framework
for developing the front-end of Web applications. With smaller apps, it's hardly worthwhile to setup precise standards for how to define action classes and flow. However, the issue of standardization becomes more important as an application grows more complex. This is especially true when there are more developers on a team—then standardization becomes crucial. Most of the functionality in Struts can be implemented in many ways using Struts and having many developers working on the same project without standards will inevitable lead to an non-homogeneous and difficult to maintain system.
If you're an experienced Struts developer looking for ways to standardize a Struts application architecture, this article offers several pieces of advice to help improve development speed and the quality of your applications.
All code shown and described in the article can be downloaded here. JDK 5.0 and Eclipse 3.1.1 has been used to test
the examples.
Extending Struts' Action Class
Every action class must extend Struts' Action class, and it's always a good idea to first create your own extension of Struts' Action class, and then let all the Action classes extend this class instead. This "application Action class," which will be referred to as "MyAction" can be used for various useful tasks:
- To control authentification and logon for the users. Since all actions go through
MyAction, it's easy to validate the users in one spot only.
- It serves as a container for various utility functions.
- It can perform logging and tracing.
Extending the Struts Action class can be illustrated by implementing a trace function that shows when every Action class is entered and exited. Since every action class must implement the execute method, the extended Action class starts like this:
import javax.servlet.http.*;
import org.apache.struts.action.*;
public abstract class MyAction extends Action {
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws Exception {
System.out.println("Entering action: " + mapping.getPath() +
" (class=" + mapping.getType() + ")");
ActionForward forward = myExecute(mapping, form, request, response);
if (forward == null) {
throw new Exception("Trying to exit with a null forward object.");
}
System.out.println("Exiting action : " + mapping.getPath() +
" (forward=" + forward.getName() +
", path=" + forward.getPath() + ")");
return forward;
}
public abstract ActionForward myExecute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws Exception;
With a setup like this, every action must extend MyAction and implement
myExecute. The trace produced by the System.out statements will be shown when the test application described below is completed.
While you're setting up MyAction, add a nice utility method called
doForward. It's used instead of the usual "return
mapping.findForward()" statement, which returns a null object if the forward string is not found. This results in a blank page in the browser—not very informative. doForward throws
an exception instead of returning a null object. The exception text describes the cause of the error.
public ActionForward doForward(
ActionMapping mapping,
String fwd) throws Exception {
ActionForward forward = mapping.findForward(fwd);
if (forward == null) {
throw new Exception("No forward defined for string=" + fwd +
" in class " + getClass().getName());
}
return forward;
}
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