The Problem with Servlets over JSP
The Problem with Servlets
In many Java servlet-based applications, processing the request and generating the response are both handled by a single servlet class.
A typical servlet class
public class OrderServlet extends HttpServlet
{
public void doGet((HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter( );
if (isOrderInfoValid(request))
{
saveOrderInfo(request);
out.println("<html>");
out.println(" <head>");
out.println(" <title>Order Confirmation</title>");
out.println(" </head>");
out.println(" <body>");
out.println(" <h1>Order Confirmation</h1>");
renderOrderInfo(request);
out.println(" </body>");
out.println("</html>");
}
...
If you're not a programmer, don't worry about all the details in this code. The point is that the servlet contains request processing and business logic (implemented by methods such as isOrderInfoValid() and saveOrderInfo( )), and also generates the response HTML code, embedded directly in the servlet code using println( ) calls. A more structured servlet application isolates different pieces of the processing in various reusable utility classes and may also use a separate class library for generating the actual HTML elements in the response. Even so, the pure servletbased approach still has a few problems:
- Thorough Java programming knowledge is needed to develop and maintain all aspects of the application, since the processing code and the HTML elements are lumped together.
- Changing the look and feel of the application, or adding support for a new type of client (such as a WML client), requires the servlet code to be updated and recompiled.
- It's hard to take advantage of web page development tools when designing the application interface. If such tools are used to develop the web page layout, the generated HTML must then be manually embedded into the servlet code, a process which is time consuming, error prone, and extremely boring.
Adding JSP to the puzzle lets you solve these problems by separating the request processing and business logic code from the presentation. Instead of embedding HTML in the code, place all static HTML in a JSP page, just as in a regular web page, and add a few JSP elements to generate the dynamic parts of the page. The request processing can remain the domain of the servlet, and the
business logic can be handled by JavaBeans and EJB components.
As I mentioned before, separating the request processing and business logic from presentation makes it possible to divide the development tasks among people with different skills. Java programmers implement the request processing and business logic pieces, web page authors implement the user interface, and both groups can use best-of-breed development tools for the task at hand. The result is a much more productive development process. It also makes it possible to change different aspects of the application independently, such as changing the business rules without touching the user interface.
Labels: Advanced Java ( Unit 4 )
posted by Swapna @ 3:04 PM
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