Tutorials : Strictly Struts :

Strictly Struts

Introduction

Hello readers. Yes this is an article on Struts. However, the purpose of this article is not to teach Struts. There are many great tutorials posted on this site and others, which have been very helpful for all others and me. In this article, I will address a few issues in development with Struts and some tricks hidden deep inside the Struts framework. This is an attempt to consolidate a few of the common problems faced in form based web application development using Struts. I will address issues with designing Action classes, multi-page form validations, handling cancel button and a few other design issues with Struts Action classes. Ok, let’s get started.

Designing Action classes

At first glance, writing Action classes is pretty simple. This just takes extending the Struts Action class and overriding the execute() method and then return the appropriate forward names so that the Struts framework can then forward the application to the next stage. After thinking a bit longer we realize there are many issues while writing your own Action classes. For example,

• What should go within the body of the execute()method? Can we perform the business logic within this method or not?
• What happens if there is an exception thrown inside the body of the execute() method?
• Can we write any other method than execute() and if yes, how do we invoke that method?

The isolation of data and display

Well, the fact is that you can do anything and everything you want to do within your Action classes. However, the overall impact analysis will show us what we should and should not do within our Action classes. Let’s take an example at this level.

Let's imagine we are creating a student registration system. The functionality we need is to be able to Create, Find, Update and Delete any particular student registration record. Now definitely, this application requires some database activity to be performed. Is it right to embed the database access code within the Action class? If you do so, the impact is that anytime you need to change the data access implementation, you have to come back to the Action class and change it. This is not desirable, as Action class should purely be used for Presentation layer and it should not care about how the data access happens. For example,

 
public class SomeAction extends Action
{
     public ActionForward execute(ActionMapping mapping, ActionForm form,
                                                HttpServletRequest req, 
HttpServletResponse res) throws Exception
{
      Connection conn = ApplicationResource.getConnection();
      String sql = “Select * from student”;
      Statement stmt = conn.createStatement();
      Resultset rs = stmt.executeQuery(str);
      List studentList = DataUtils.getList(rs);
      session.setAttribute(“studentList”, studentList);
      return mapping.findForward(“success”);
  }
 
}

The previous code is an example of the bad practice of embedding business process within the Action class.

Let's think why the MVC pattern came about. The sole purpose is to achieve a clear separation between presentation and data. By embedding the data access code within Action classes, we lose such separation. In the end, how will the Action classes interact with the data access layer? The answer is to use a Business Delegate object to perform such operations. So the first principle we learn here is:

Lesson 1: Action classes must always strictly follow the presentation related activities and should not perform any business process. Use a Business Delegate to perform any business specific operations.

How to Add Java Applets to Your Site

New on the Java Boutique:

New Review:

Time Management Made Easy with the Quartz Enterprise Job Scheduler
Why not just use the Java timer API? This open source scheduling API boasts simplicity, ease-of-integration, a well-rounded feature set, and it's free!

New Applet:

Reverse Complement
Reverse Complement is a simple applet that converts DNA or RNA sequences into three useful formats.

Elsewhere on internet.com:

WebDeveloper Java
Lots of Java information on webdeveloper.com

WDVL Java
Thorough Java resource at the Web Developer's Virtual Library.

ScriptSearch Java
Hundreds of free Java code files to download.

jGuru: Your View of the Java Universe
Customizable portal with online training, FAQs, regular news updates, and tutorials.