JavaScript学习4---ajax的使用

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JavaScript学习4---ajax的使用

function getXMLHttpRequest(){
    //IE浏览器
    var client = getXMLHttpRequestFromIE();
    if(client == null){
        //非IE浏览器
        client = new XMLHttpRequest();
    }

    return client;
}

function getXMLHttpRequestFromIE(){
    var namePrefixes = ["Msxml3", "Msxml2", "Msxml", "Microsoft"];
    for(var i = 0; i < namePrefixes.length; i++){
        var name = namePrefixes[i] + ".XMLHTTP";
        try{
          return new ActiveXObject(name);
        }catch(e){
        }
    }

    return null;
}

jsp文件：

<%@ page pageEncoding="gbk"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath}/style/style.css"></link>
<style type="text/css">

    #content div{
   margin: 10px 0px;
}

div.submit{
   text-align:center;
}

label{
   80px;
   display:block;
   float:left;
}

fieldset{
      300px;
      margin:auto;
      margin-top:20px;
      display:block;
}

fieldset select{
   120px;
}

fieldset input{
   120px;
}

</style>
<title>登录</title>
<script type="text/javascript" src="${pageContext.request.contextPath}/js/client.js"></script>
<script type="text/javascript">
        var client = getXMLHttpRequest();

        function login(form){
            var username = form.username.value;
            var password = form.password.value;

            var requestURL = "${pageContext.request.contextPath}/login.do?username=" + username + "&password=" + password;
            requestURL += "&time=" + new Date().getTime();

            client.open("GET", requestURL, true);
            client.onreadystatechange = function(){
                if(client.readyState == 4){
                    if(client.status == 200){
                        var result = parseInt(client.responseText);
                        if(result == 0){
                               document.getElementById("message").innerHTML = "用户不存在或密码不正确!" ;
                        }else{
                          window.location = "${pageContext.request.contextPath}/memberCenter.jsp";
                        }
                    }
                }
            }
            client.send(null);
        }

        function clearMessage(){
            document.getElementById("message").innerHTML = "";
        }
</script>
</head>
<body>
<div id="container">
<div id="header">
    <ul>
      <li><a href="#">帮助</a></li>
    </ul>
</div>
<div id="menu">
    <ul>
      <li><a href="index.html">首页</a></li>
      <li><a href="roomPrice.html">设施与价格</a></li>
      <li><a href="memberCenter.html">会员中心</a></li>
    </ul>
</div>
<div id="content">
<form>
    <fieldset>
      <legend>登录信息</legend>
      <div>
        <label for="username">用户名</label>
        <input type="text" name="username" id="username" onfocus="clearMessage()"/>
      </div>
      <div>
        <label for="password">密码</label>
        <input type="text" name="password" id="password"   onfocus="clearMessage()"/>
      </div>
    </fieldset>
    <div id="message"></div>
    <div class="submit">
      <input type="button" value="登录" onclick="login(this.form)"/>
      <p>如果您还没有注册，请<a href="${pageContext.request.contextPath}/register.jsp">点击这里注册</a>成为会员。</p>
    </div>
</form>
</div>
<hr />
<div id="footer">
    <p>本系统做为Java Web教学设计使用。未经允许，不得做为它用，版权所有Allan<br />联系方式：javamedia@live.cn</p>
</div>
</div>
</body>
</html>

servlet 代码

package action;

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;
import javax.servlet.http.HttpSession;

import util.RequestUtil;
import biz.Member;
import biz.MemberBiz;

public class ActionServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  String path = request.getServletPath();
  path = path.substring(0, path.indexOf("."));
  if (path.equals("/register")) {
   register(request, response);
  } else if (path.equals("/login")) {
   login(request, response);
  } else if (path.equals("/validateusername")) {
   validateUsername(request, response);
  }
}

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

public void register(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  Member member = new Member();
  RequestUtil.setProperties(request, member);
  MemberBiz memberBiz = new MemberBiz();
  Member m = memberBiz.find(member.getUsername());
  if (m != null) {
   request.setAttribute("message", "username " + m.getUsername()
     + " has already existed.");
   getServletContext().getRequestDispatcher("/register.jsp").forward(
     request, response);
  } else {
   memberBiz.add(member);
   getServletContext().getRequestDispatcher("/success.jsp").forward(
     request, response);
  }
}

public void validateUsername(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  response.setContentType("text/plain;charset=gbk");
  PrintWriter out = response.getWriter();

  String username = request.getParameter("username");
  MemberBiz memberBiz = new MemberBiz();
  Member m = memberBiz.find(username);
  if (m == null) {
   out.println(0);
  } else {
   out.println(1);
  }
  out.close();
}

public void login(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  response.setContentType("text/plain;charset=gbk");
  PrintWriter out = response.getWriter();

  String username = request.getParameter("username");
  String password = request.getParameter("password");
  MemberBiz memberBiz = new MemberBiz();
  Member m = memberBiz.find(username, password);
  if(m == null){
   out.println(0);
  }else{
   HttpSession session = request.getSession();
   session.setAttribute("user", m);
   out.println(1);
  }
  out.close();
}

}

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原文地址：https://www.cnblogs.com/alaricblog/p/3278294.html