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：

 package com.qls2;

 import java.io.IOException;
 import java.io.PrintWriter;
 import java.net.URLDecoder;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 public class ClientA extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();
         String clientB = request.getParameter("sixi");

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

out.println(clientB);

         out.println("<h1>欧阳凤</h1>");
         out.println("<form action='/servletContext/CreateServletContext2' method='post'>");
         out.println("请输入：<input type='text' name='ouyangfeng'/>");
         out.println("<input type='submit' value='发送'/>");
         out.println("</form>");
     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();
         this.doGet(request, response);
     }

 }

//CreateServletContext2 的代码如下：

 package com.qls2;
 /**
  * 用ServletContext制作一个聊天室。
  */
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.net.URLEncoder;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 public class CreateServletContext2 extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();
         //获取ClientA输入的内容：
         String clientA = request.getParameter("ouyangfeng");

         this.getServletConfig().getServletContext().setAttribute("secreteriat", clientA);
         request.getRequestDispatcher("/ReadServletContext2").forward(request, response);
     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();
         this.doGet(request, response);
     }

 }

//ReadServletContext2的代码如下：

 package com.qls2;

 import java.io.IOException;
 import java.io.PrintWriter;
 import java.net.URLDecoder;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 public class ReadServletContext2 extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();
         String str=(String) this.getServletContext().getAttribute("secreteriat");

         out.println(str);
         out.println("<h1>泗溪</h1>");
         out.println("<form action='/servletContext/ClientA' method='post'>");
         out.println("请输入：<input type='text' name='sixi'/>");
         out.println("<input type='submit' value='发送'/>");
         out.println("</form>");

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         PrintWriter out = response.getWriter();
         this.doGet(request, response);
     }

 }