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68

Chapter 3 Handling the Client Request: Form Data

Figures 3 1 and 3 2 show the result of the HTML front end and the serv 

let, respectively. 

Listing 3.1 ThreeParams.java 

package coreservlets;

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class ThreeParams extends HttpServlet {

  public void doGet(HttpServletRequest request,

                    HttpServletResponse response)

      throws ServletException, IOException {

    response.setContentType("text/html");

    PrintWriter out = response.getWriter();

    String title = "Reading Three Request Parameters";

    out.println(ServletUtilities.headWithTitle(title) +

                "\n" +

                "
" + title + "
\n" +

                "
\n" +

                "  
param1: "

                + request.getParameter("param1") + "\n" +

                "  
param2: "

                + request.getParameter("param2") + "\n" +

                "  
param3: "

                + request.getParameter("param3") + "\n" +

                "\n" +

                "");

  }

}

Although you are required to specify response settings (see Chapters 6 and

7) before beginning to generate the content, there is no requirement that you

read the request parameters at any particular time. 

If you're accustomed to the traditional CGI approach where you read

POST

 data through the standard input, you should note that you can do the

same thing with servlets by calling 

getReader

 or 

getInputStream

 on the

HttpServletRequest

 and then using that stream to obtain the raw input.

This is a bad idea for regular parameters since the input is neither parsed

(separated into entries specific to each parameter) nor URL decoded

(translated so that plus signs become spaces and %XX gets replaced by the

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.