Home >Web Front-end >JS Tutorial >Two ways to solve unnecessary refresh using Ajax
Below I will bring you two methods of Ajax to solve redundant refreshes. Let me share it with you now and give it as a reference for everyone.
The controller Servlet provides simple changes:
For Ajax systems, the server response does not need to be the entire page content, it can just be
Required data, the controller cannot forward the data request to the jsp page.
The controller has two options at this time:
1. Directly generate simple response data.
In this mode, the Servlet directly obtains the page output stream through response and generates a character response through the
output stream.
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. Turn to a simple jsp and use the JSP page to generate a simple response.
The controller forwards the request to another JSP page, and the JSP page is only responsible for outputting chat information
Here you need a jsp page to receive the information sent by the controller The data is also the server's response text, and on the
original page, just:
1) Create an XMLHttpRequest object
2) Send a request
3) Receive the server’s response
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=http://www.jb51.net>脚本之家</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);
}
}Page to receive data
<%@ page contentType="text/html;charset=GBK" errorPage="error.jsp"%>
<%-- 输出当前的聊天信息 --%>
${requestScope.chatList}html page
<!DOCTYPE html>
<html>
<head>
<meta name="author" content="Yeeku.H.Lee(CrazyIt.org)" />
<meta http-equiv="Content-Type" content="text/html; charset=GBK" />
<title>聊天页面</title>
</head>
<body onload="sendEmptyRequest();">
<p style="width:780px;border:1px solid black;text-align:center">
<h3>聊天页面</h3>
<p>
<textarea id="chatArea" name="chatArea" cols="90"
rows="30" readonly="readonly"></textarea>
</p>
<p align="center">
<input id="chatMsg" name="chatMsg" type="text"
size="90" onkeypress="enterHandler(event);"/>
<input type="button" name="button" value="提交"
onclick="sendRequest();"/>
</p>
</p>
<script type="text/javascript">
var input = document.getElementById("chatMsg");
input.focus();
var XMLHttpReq;
// 创建XMLHttpRequest对象
function createXMLHttpRequest()
{
if(window.XMLHttpRequest)
{
// DOM 2浏览器
XMLHttpReq = new XMLHttpRequest();
}
else if (window.ActiveXObject)
{
// IE浏览器
try
{
XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try
{
XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e)
{
}
}
}
}
// 发送请求函数
function sendRequest()
{
// input是个全局变量，就是用户输入聊天信息的单行文本框
var chatMsg = input.value;
// 完成XMLHttpRequest对象的初始化
createXMLHttpRequest();
// 定义发送请求的目标URL
var url = "chat.do";
// 通过open方法取得与服务器的连接
// 发送POST请求
XMLHttpReq.open("POST", url, true);
// 设置请求头-发送POST请求时需要该请求头
XMLHttpReq.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded");
// 指定XMLHttpRequest状态改变时的处理函数
XMLHttpReq.onreadystatechange = processResponse;
// 清空输入框的内容
input.value = "";
// 发送请求，send的参数包含许多的key-value对。
// 即以：请求参数名=请求参数值 的形式发送请求参数。
XMLHttpReq.send("chatMsg=" + chatMsg);
}
//定时请求服务器
function sendEmptyRequest()
{
// 完成XMLHttpRequest对象的初始化
createXMLHttpRequest();
// 定义发送请求的目标URL
var url = "chat.do";
// 发送POST请求
XMLHttpReq.open("POST", url, true);
// 设置请求头-发送POST请求时需要该请求头
XMLHttpReq.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded");
// 指定XMLHttpRequest状态改变时的处理函数
XMLHttpReq.onreadystatechange = processResponse;
// 发送请求,，不发送任何参数
XMLHttpReq.send(null);
// 指定0.8s之后再次发送请求
setTimeout("sendEmptyRequest()" , 800);
}
// 处理返回信息函数
function processResponse()
{
// 当XMLHttpRequest读取服务器响应完成
if (XMLHttpReq.readyState == 4)
{
// 服务器响应正确（当服务器响应正确时，返回值为200的状态码）
if (XMLHttpReq.status == 200)
{
// 使用chatArea多行文本域显示服务器响应的文本
document.getElementById("chatArea").value
= XMLHttpReq.responseText;
}
else
{
// 提示页面不正常
window.alert("您所请求的页面有异常。");
}
}
}
function enterHandler(event)
{
// 获取用户单击键盘的“键值”
var keyCode = event.keyCode ? event.keyCode
: event.which ? event.which : event.charCode;
// 如果是回车键
if (keyCode == 13)
{
sendRequest();
}
}
</script>
</body>
</html>The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
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