Section 3.5.3,  Accessing DB2 via JDBC  on page 83 provides a

discussion on accessing DB2 database using the servlet.

  Section 3.5.4,  Accessing Domino data in Linux with Java  on page 93

discusses the way we access a Domino data using the servlet.

3.5.1 Servlets

Servlet is the Java replacement of the cgi programming for Java enabled Web

servers. The servlet can be viewed as a server side Java program that

performs enhanced functions for the Web server. Servlet is implemented

based on the Sun specification that can be found at:

http://java.sun.com/docs/servlet

The following codes are required when creating a servlet:

  Creating a Java servlet requires the following imports:

import javax.servlet.*;

import javax.servlet.http.*

  The class must extend the HttpServlet class as follows:

public class  extends HttpServlet

  We must at least implement either the doGet or doPost method.

Therefore, the minimal code required to implement a servlet and service an

HTTP POST request is shown in Figure 65.

import javax.servlet.*;

import javax.servlet.http.*;

public class UselessServlet extends HttpServlet {

public void doPost(HttpServletRequest req, HttpServletResponse res)

throws ServletException {

// service POST here

}

}

Figure 65. Minimum code for servlet implementing HTTP GET request

As another example, we want to implement both GET and POST operation

similarly. Since both methods will access the same code base, we

accomplish this by implementing both doGet and doPost and passing the

parameters to another method called doService. This is illustrated by the

code in Figure 66 on page 80.

Chapter 3. Building the Web server

79