XMLHttpRequest与Java Servlet交互示例-优快云博客

//main.jsp



<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>xmlhttp请求Java Servlet</title>
</head>
<script type="text/javascript" language="javascript">
	function createXmlRequest(){
		var xmlreq=false;
		if(window.XMLHttpRequest){
			xmlreq=new XMLHttpRequest();
		}else if(window.ActiveXObject){
			try{
				xmlreq=new ActiveXObject("Msxml2.XMLHTTP");
			}catch(e1){
				try{
					xmlreq=new ActiveXObject("Microsoft.XMLHTTP");
				}catch(e2){

				}
			}
		}
		return xmlreq;
	}

	function userNameCheck(){
		var username=document.all.username.value;
		var request=createXmlRequest();
		alert(username);
		alert("上面这是页面的值");
		request.open("post","UserAction?username="+username);
		alert(username);
		request.send();
		request.onreadystatechange=function(){
			if(request.readyState==4)
				if(request.status==200){
					var value=request.responseText;
					alert("传回java段验证的值");
					alert(value);
					if(value=="true"){
						document.all.unc.innerHTML="该用户名已存在";
					}else{
						document.all.unc.innerHTML="OK";
					}
				}

		}
	}


</script>
<body>
用户姓名：
<input type="text" name="username" onblur="userNameCheck()"/>
<font color="red" size="-1" id="unc"></font>


</body>
</html>

//UserAction


package com.java.page;

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

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

public class UserAction extends HttpServlet{
	public UserAction(){
		super();
	}
	protected void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
		this.doPost(request, response);
	}
	protected void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
		response.setContentType("text/html");
		response.setCharacterEncoding("utf-8");
		String username=request.getParameter("username");
	//	if("abin".equals(username)){
			if(username.equals("abin")){
			response.getWriter().print("true");
		//	response.getWriter().write(true);
		}else{
		//	response.getWriter().print(false);
			response.getWriter().print("false");
		}


	}
}

//web.xml


<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

 	<servlet>
 		<servlet-name>UserAction</servlet-name>
 		<servlet-class>com.java.page.UserAction</servlet-class>
 	</servlet>


	<servlet-mapping>
		<servlet-name>UserAction</servlet-name>
		<url-pattern>/UserAction</url-pattern>
	</servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

Ajax Servlet