用ServletContext做一个简单的聊天室

这里主要是ServletContext的一个特性：ServletContext是一个公共的空间，可以被所有的客户访问。由此可见ServletContext比cookie和session的作用范围要大【session,cookie，和ServletContext是Servlet中比较重要的几个对象】

用ServletContext做一个简单的聊天室的思路是：把客户欧阳凤所输入的内容，保存在ServletContext中，在客户泗溪中用ServletContext的方法，获取客户欧阳凤所输入的内容。同时，在客户欧阳凤的界面得到客户泗溪所输入的内容。

两个客户的运行时的界面如图所示：

//ClientA的代码如下：

 1 package com.qls2;
 2 
 3 import java.io.IOException;
 4 import java.io.PrintWriter;
 5 import java.net.URLDecoder;
 6 
 7 import javax.servlet.ServletException;
 8 import javax.servlet.http.HttpServlet;
 9 import javax.servlet.http.HttpServletRequest;
10 import javax.servlet.http.HttpServletResponse;
11 
12 public class ClientA extends HttpServlet {
13 
14     
15     public void doGet(HttpServletRequest request, HttpServletResponse response)
16             throws ServletException, IOException {
17 
18         response.setContentType("text/html;charset=utf-8");
19         PrintWriter out = response.getWriter();
20         String clientB = request.getParameter("sixi");
21       
22

String clientB = request.getParameter("sixi");
if (clientB!=null) {
byte[] b = clientB.getBytes("iso-8859-1");
clientB = new String(b, "utf-8");
}

out.println(clientB);

23         out.println("<h1>欧阳凤</h1>");
24         out.println("<form action='/servletContext/CreateServletContext2' method='post'>");
25         out.println("请输入：<input type='text' name='ouyangfeng'/>");
26         out.println("<input type='submit' value='发送'/>");
27         out.println("</form>");
28     }
29 
30     
31     public void doPost(HttpServletRequest request, HttpServletResponse response)
32             throws ServletException, IOException {
33 
34         response.setContentType("text/html;charset=utf-8");
35         PrintWriter out = response.getWriter();
36         this.doGet(request, response);
37     }
38 
39 }

//CreateServletContext2 的代码如下：

 1 package com.qls2;
 2 /**
 3  * 用ServletContext制作一个聊天室。
 4  */
 5 import java.io.IOException;
 6 import java.io.PrintWriter;
 7 import java.net.URLEncoder;
 8 
 9 import javax.servlet.ServletException;
10 import javax.servlet.http.HttpServlet;
11 import javax.servlet.http.HttpServletRequest;
12 import javax.servlet.http.HttpServletResponse;
13 
14 public class CreateServletContext2 extends HttpServlet {
15 
16     public void doGet(HttpServletRequest request, HttpServletResponse response)
17             throws ServletException, IOException {
18 
19         response.setContentType("text/html;charset=utf-8");
20         PrintWriter out = response.getWriter();
21         //获取ClientA输入的内容：
22         String clientA = request.getParameter("ouyangfeng");
23         
24         this.getServletConfig().getServletContext().setAttribute("secreteriat", clientA);
25         request.getRequestDispatcher("/ReadServletContext2").forward(request, response);
26     }
27 
28     
29     public void doPost(HttpServletRequest request, HttpServletResponse response)
30             throws ServletException, IOException {
31 
32         response.setContentType("text/html;charset=utf-8");
33         PrintWriter out = response.getWriter();
34         this.doGet(request, response);
35     }
36 
37 }

//ReadServletContext2的代码如下：

 1 package com.qls2;
 2 
 3 import java.io.IOException;
 4 import java.io.PrintWriter;
 5 import java.net.URLDecoder;
 6 
 7 import javax.servlet.ServletException;
 8 import javax.servlet.http.HttpServlet;
 9 import javax.servlet.http.HttpServletRequest;
10 import javax.servlet.http.HttpServletResponse;
11 
12 public class ReadServletContext2 extends HttpServlet {
13 
14     
15     public void doGet(HttpServletRequest request, HttpServletResponse response)
16             throws ServletException, IOException {
17 
18         response.setContentType("text/html;charset=utf-8");
19         PrintWriter out = response.getWriter();
20         String str=(String) this.getServletContext().getAttribute("secreteriat");
21         
22         out.println(str);
23         out.println("<h1>泗溪</h1>");
24         out.println("<form action='/servletContext/ClientA' method='post'>");
25         out.println("请输入：<input type='text' name='sixi'/>");
26         out.println("<input type='submit' value='发送'/>");
27         out.println("</form>");
28         
29     }
30 
31     
32     public void doPost(HttpServletRequest request, HttpServletResponse response)
33             throws ServletException, IOException {
34 
35         response.setContentType("text/html;charset=utf-8");
36         PrintWriter out = response.getWriter();
37         this.doGet(request, response);
38     }
39 
40 }