Ajax解决多余刷新的两种方法(总结)

控制器Servlet则提供了简单的改变：

对于Ajax系统而言，服务器响应无须是整个页面内容，可以仅是

必需的数据，控制器不能将数据请求转发到jsp页面。

此时控制器有两个选择：

1、直接生成简单的响应数据。

在这种模式下，Servlet直接通过response获取页面输出流，通过

输出流生成字符响应。

package pers.zkr.chat.web;

import java.io.IOException;
import java.io.PrintWriter;

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

import pers.zkr.chat.service.ChatService;


@WebServlet(urlPatterns={"/chat.do"})
public class ChatServlet extends HttpServlet {

 @Override
 public void service(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {
 // TODO Auto-generated method stub
 
 request.setCharacterEncoding("utf-8");
 
 
 String msg=request.getParameter("chatMsg");
 System.out.println(msg);
 
 if(msg!=null&&!msg.equals("")){
  String user=(String)request.getSession().getAttribute("user");
  System.out.println(user+"user");
  ChatService.instance().addMsg(user, msg);
  
 }
 
 //设置响应内容的类型
 <strong>response.setContentType("text/html;charset=utf-8");
 // 获取页面输出流
 PrintWriter out = response.getWriter();
 //直接生成响应
 out.println(ChatService.instance().getMsg());</strong>
 
 request.setAttribute("msg",ChatService.instance().getMsg());
 
 forward("/chat.jsp", request , response);
 }

 private void forward(String url, HttpServletRequest request,
  HttpServletResponse response) throws ServletException, IOException {
 // TODO Auto-generated method stub
 
 request.getRequestDispatcher(url)
   .forward(request , response);  
 }
 
}    

2、转向一个简单的jsp使用JSP页面生成简单的响应。

控制器将请求转发到另外的JSP页面，而JSP页面仅仅负责输出聊天信息

在这里需要一个jsp页面来接收控制器发来的数据，也是服务器的响应文本，而在

原来的页面，只需：

1）创建XMLHttpRequest对象

2) 发送请求

3）接收服务器的响应

package org.crazyit.chat.web;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;

import java.io.*;

import org.crazyit.chat.service.*;

/**
 * Description:
 * <br/>网站: <a href=//www.jb51.net>易采站长站</a>
 * <br/>Copyright (C), 2001-2014, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @version 1.0
 */
@WebServlet(urlPatterns={"/chat.do"})
public class ChatServlet extends HttpServlet
{
 public void service(HttpServletRequest request,
 HttpServletResponse response)throws IOException,ServletException
 {
 // 设置使用GBK字符集来解析请求参数
 request.setCharacterEncoding("utf-8");
 String msg = request.getParameter("chatMsg");
 if ( msg != null && !msg.equals(""))
 {
  // 取得当前用户
  String user = (String)request.getSession(true)
  .getAttribute("user");
  // 调用ChatService的addMsg来添加聊天消息
  ChatService.instance().addMsg(user , msg);
 }
 // 将全部聊天信息设置成request属性
 <strong>request.setAttribute("chatList" ,
  ChatService.instance().getMsg());</strong>
 // 转发到chatreply.jsp页面
 forward("/chatreply.jsp" , request , response);
 }
 // 执行转发请求的方法
 private void forward(String url , HttpServletRequest request,
 HttpServletResponse response)throws ServletException,IOException
 {
 // 执行转发
 request.getRequestDispatcher(url)
  .forward(request,response);
 }
}

								 
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