1、创建index.jsp页面如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>2、js文件如下：
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script type="text/javascript" src="js/index.js"></script>
</head>
<body>
<form action="CheckUserName" method="post">
用户名：<input type="text" id="userName" onblur="checkUserName(this.value)" />
<lable id="result"></lable><br/>
密 码：<input type="password" name="password" />
</form>
<br/>
</body>
</html>
function createAjax(){
var ajax = null;
try{
ajax = new XMLHttpRequest();
}catch(e1){
var versions=['Microsoft.XMLHTTP', 'MSXML.XMLHTTP', 'Msxml2.XMLHTTP.7.0','Msxml2.XMLHTTP.6.0','Msxml2.XMLHTTP.5.0', 'Msxml2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP'];
for(var i = 0;i<versions.length;i++){
try{
ajax = new ActiveXObject(versions[i]);
break;
}catch(ex){
}
}
}
return ajax;
}
function checkUserName(value){
var ajax = new createAjax();
ajax.open("GET","servlet/CheckUserName?userName="+value);
ajax.onreadystatechange = function(){
if(ajax.readyState==4&&ajax.status==200){
document.getElementById("result").innerHTML = ajax.responseText;
}
}
ajax.send();
}
3、逻辑处理的servlet
package edu.uestc.servlet;配置文件如下：
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 CheckUserName extends HttpServlet {
/**
* Constructor of the object.
*/
public CheckUserName() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//System.out.println("Do Get......");
String username = request.getParameter("userName");
//解决Get方法的乱码问题
username = new String(username.getBytes("ISO-8859-1"), "UTF-8");
System.out.println(username);
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
if ("zsz".equals(username)){
out.println("用户名重复");
}else{
out.println("用户名可用");
}
out.flush();
out.close();
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// Put your code here
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
<servlet>
<servlet-name>CheckUserName</servlet-name>
<servlet-class>edu.uestc.servlet.CheckUserName</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CheckUserName</servlet-name>
<url-pattern>/servlet/CheckUserName</url-pattern>
</servlet-mapping>