JAVA

Finishing the Project: Java Web Development in Eclipse and Tomcat

Last week, I introduced you to some of the fundamental concepts you need for working with Java web components. For this project we'll be working with JSP and servlets. I walked you through getting the appropriate downloads installed and setting up your work space. We stopped after just creating the web project. In this part, we will add our content, including HTML, JSP, and servlets.

Author Info:

By: Gangyi

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May 29, 2007

TABLE OF CONTENTS:

<% Œ
String secreteUser = "user";
String secretePass = "pass";
String username = request.getParameter("username"); Ž
String password = request.getParameter("password");
%>
<%if(!(username.equals(secreteUser) || password.equals(secretePass))) {%>
Wrong username / password
<%} else {%>
Welcome aboard <%=username%>!
<%}%> '

Now you have figured out the relationship between JSP and Servlet! Let's go a step further to prove that JSP actually is the text form of the Servlet class.

package org.apache.jsp;

import Javax.servlet.*;
import Javax.servlet.http.*;
import Javax.servlet.jsp.*;

public final class welcome_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {

private static Java.util.Vector _jspx_dependants;

public Java.util.List getDependants() {
return _jspx_dependants;
}

public void _jspService(HttpServletRequest request, HttpServletResponse response)
throws Java.io.IOException, ServletException {

    JspFactory _jspxFactory = null;
    PageContext pageContext = null;
    HttpSession session = null;
    ServletContext application = null;
    ServletConfig config = null;
    JspWriter out = null;
    Object page = this;
    JspWriter _jspx_out = null;
    PageContext _jspx_page_context = null;

    try {
      _jspxFactory = JspFactory.getDefaultFactory();
      response.setContentType("text/html");
      pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("<html>n");
      out.write("<head>rn");
      out.write("n");
      out.write("<title>Welcome page</title>n");
      out.write("</head>n");
      out.write("<body>rn");
      out.write("<pre>n");

      String secreteUser = "user";
      String secretePass = "pass";
      String username = request.getParameter("username");
      String password = request.getParameter("password");

      out.write('r');
      out.write('n');
      if(!(username.equals(secreteUser) || password.equals(secretePass))) {
        out.write("rn");
        out.write("Wrong username / passwordrn");
      } else {
        out.write("rn");
        out.write("Welcome aboard ");
        out.print(username);
        out.write(" !rn");
      }
      out.write("rn");
      out.write("</pre>n");
      out.write("</body>n");
      out.write("</html>");
    } catch (Throwable t) {
      if (!(t instanceof SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          out.clearBuffer();
        if (_jspx_page_context != null)
          _jspx_page_context.handlePageException(t);
      }
    } finally {
        if (_jspxFactory != null)
          _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

Now let's do a little more work to prove that JSP actually is a Servlet. Modify login.html's form part

Next, expand WebContent -> WEB-INF, and Click web.xml. This is the web application configuration file. Modify the content to the following:

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>JavaWebDev_Tutorial_1</display-name>
<servlet>
    <description></description>
    <display-name>welcome_jsp</display-name>
    <servlet-name>welcome_jsp</servlet-name>
    <servlet-class>org.apache.jsp.welcome_jsp</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>welcome_jsp</servlet-name>
    <url-pattern>/welcome_jsp</url-pattern>
</servlet-mapping>
</web-app>

The web.xml defines the Servlet we just imported from and the servlet-mapping's url-pattern pointed to the org.apache.jsp.welcome_jsp.welcome_jsp servlet with the short name welcome_jsp corresponding to login.htm action part here:

If you run the application again, you'll get the same result.

To explain it further, the welcome_jsp actually extends org.apache.jasper.runtime.HttpJspBase

public final class welcome_jsp extends org.apache.jasper.runtime.HttpJspBase

Here is the class hierarchy:

(http://tomcat.apache.org/tomcat-4.1-
doc/jasper/docs/api/org/apache/jasper/runtime/HttpJspBase.html)

java.lang.Object
extended by javax.servlet.GenericServlet
javax.servlet.http.HttpServlet
org.apache.jasper.runtime.HttpJspBase

So the welcome_jsp is indeed a Servlet and it's generated from welcome.jsp by the Eclipse environment.

Summary

In this short tutorial, we introduced the Integrated Java Web Development environment with Eclipse and how to develop, test, and configure a web application. We are ready to move to the next in upcoming articles.

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