ajax异步调用

1、构建数据库连接的工具类

package com.icss.DAO;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.Statement;import java.util.Properties;import javax.naming.Context;import javax.naming.InitialContext;import javax.sql.DataSource;/** * 类的作用是加载驱动，建立连接，释放资源，增删改操作 * @author fly * */public class BaseDao {    //创建一个连接对象，返回connection    public static Connection getConnection(){        Connection connection = null;        //从连接池中取连接对象        Context cxtContext = null;        DataSource dsDataSource = null;        try {            cxtContext = new InitialContext();            dsDataSource = (DataSource)cxtContext.lookup("java:comp/env/myschoolConn");            connection = dsDataSource.getConnection();        } catch (Exception e) {            System.out.println("连接不成功");        }        return connection;    }    public static boolean executeUpdate(String sql,Object ...obj){        Connection connection  = getConnection();        PreparedStatement pst = null;        int result = 0;        try {            pst = connection.prepareStatement(sql); //预编译            //判断是否有参数传入，如果没有，则obj数组是null            if(obj!=null){                for(int i =0;i<obj.length;i++){                    pst.setObject(i+1, obj[i]);                }            }                           result = pst.executeUpdate();        } catch (Exception e) {            System.out.println("数据库增删改有问题");        }finally{            closeAll(connection,pst,null);        }        return result>0;    }    public static void closeAll(Connection conn,Statement st,ResultSet rs){        try {            if(rs!= null) rs.close();            if(st!= null)st.close();            if(conn!=null) conn.close();        } catch (Exception e) {            System.out.println("关闭资源");        }    }}

2、连接池的设置
在WebRoot下的META-INF中创建一个context.xml文件

<?xml version='1.0' encoding='utf-8'?><Context><Resource         name ="myschoolConn"        auth="Container"        type="javax.sql.DataSource"        maxActive="100"        maxIdle="30"        maxWait="10000"        username="root"        password="123456"        driverClassName="com.mysql.jdbc.Driver"        url="jdbc:mysql://127.0.0.1:3306/myschool?characterEncoding=utf-8"/></Context>

3、创建Ajaxl对象

package com.icss.entity;public class Admin {    private int id;    private String loginId;    private String loginPwd;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getLoginId() {        return loginId;    }    public void setLoginId(String loginId) {        this.loginId = loginId;    }    public String getLoginPwd() {        return loginPwd;    }    public void setLoginPwd(String loginPwd) {        this.loginPwd = loginPwd;    }}

4、创建dao层方法

package com.icss.DAO;import com.icss.entity.Admin;public interface AdminDao {    public Admin getAdminByLoginId(String loginId);}

5、dao层方法的实现

package com.icss.Imp;import java.sql.Connection;import java.sql.ResultSet;import java.sql.Statement;import com.icss.DAO.AdminDao;import com.icss.DAO.BaseDao;import com.icss.entity.Admin;public class AdminDaoImp implements AdminDao {    @Override    public Admin getAdminByLoginId(String loginId) {        Connection connection = BaseDao.getConnection();        Statement statement = null;        ResultSet resultSet = null;        Admin admin = null;        String sqlString = "select * from admin where loginid = '"+loginId+"'";        try {            statement = connection.createStatement();            resultSet = statement.executeQuery(sqlString);            if(resultSet.next()){                admin = new Admin();                admin.setId(resultSet.getInt(1));                admin.setLoginId(resultSet.getString(2));                admin.setLoginPwd(resultSet.getString(3));            }        } catch (Exception e) {        }finally{            BaseDao.closeAll(connection, statement, resultSet);        }        return admin;    }}

6、调用dao层方法

package com.icss.service;import com.icss.DAO.AdminDao;import com.icss.Imp.AdminDaoImp;import com.icss.entity.Admin;public class AdminService {    AdminDao dao = new AdminDaoImp();    public Admin getAdminByLoginId(String loginId){        return dao.getAdminByLoginId(loginId);    }}

7、Servlet方法

package com.icss.Servlet;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 com.icss.entity.Admin;import com.icss.service.AdminService;public class AdminServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        String loginId = request.getParameter("loginId");        Admin admin = new AdminService().getAdminByLoginId(loginId);        if(admin == null){  //表示用户名不存在，则用户名可用            //向客户端返回信息            response.getWriter().write("yes");        }else{  //表示用户名不可用            response.getWriter().write("no");        }    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

8、采用JavaScript实现

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%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%>">    <style>        #div1{width:400px;margin:0 auto;}       </style>    <script type="text/javascript">        //1、获取XMLHttpRequest对象的函数        function getXMLHttpRequest(){            if(window.XMLHttpRequest){                return new XMLHttpRequest();            }        }        var xhr;        //文本框失去焦点触发函数        function inputLogin(txt){            xhr = getXMLHttpRequest();  //调用方法创建XMLHttpRequest对象            var loginId = txt.value;    //取文本框的值            xhr.onreadystatechange=resultFunction; //设置回调函数            //初始化XMLHttpRequest对象            xhr.open("GET", "AdminServlet?loginId="+loginId,true);            //XMLHttpRequest对象发送请求            xhr.send(null);        }        //回调函数        function resultFunction(){            var s = document.getElementById("s");            if(xhr.readyState == 4){                if(xhr.status == 200){                    var data = xhr.responseText;                    if(data == "yes"){                        s.style.color = "green";                        s.innerHTML="用户名可用";                    }else{                        s.style.color = "red";                        s.innerHTML="用户名已存在";                    }                }            }        }    </script>  </head>  <body>    <div id="div1">        <h2>管理员添加</h2>        <from action="" method="post">            <fieldset>                <legend>注册信息</legend>                <p>用户名:<input type="text" name="loginId"onblur="inputLogin(this)" id="loginId"/><span id="s"></span></p>                <p>密    码:<input type="password" name="loginPwd"/></p>                <p><input type="submit" value="注册"></p>            </fieldset>        </from>     </div>  </body></html>

9、采用jquery实现
方法一：

    <script type="text/javascript">        //文本框失去焦点触发函数        function inputLogin(txt){            var id = $("#loginId").val(); //取文本框值            var sp = $("#s"); //取span标签            $.ajax({                type:"GET",                url:"AdminServlet",                data:"loginId="+id,                dataType:"text",                success:function(d){                    if(d == "yes"){                        sp.css("color","green").html(" 用户名可用...");                    }else{                        sp.css("color","red").html(" 用户名已存在...");                    }                }            });        }    </script>

方法二：
通过get方法

function inputLogin(txt){            var id = $("#loginId").val(); //取文本框值            var sp = $("#s"); //取span标签            $.get(                "AdminServlet",                {loginId:id},                function(d){                    if(d == "yes"){                        sp.css("color","green").html(" 用户名可用!");                    }else{                        sp.css("color","red").html(" 用户名已存在!");                    }                },                "text"            );        }

也可以用post方法

function inputLogin(txt){            var id = $("#loginId").val(); //取文本框值            var sp = $("#s"); //取span标签            $.post(                "AdminServlet",                {loginId:id},                function(d){                    if(d == "yes"){                        sp.css("color","green").html(" 用户名可用!");                    }else{                        sp.css("color","red").html(" 用户名已存在!");                    }                },                "text"            );        }