JSP通过ajax调用servlet，servlet调用service，service调用dao，dao调用数据库；然后数据库->dao->service->servlet-(json)->jsp
法玮
一、Regist.jsp（Regist.jsp调用AccountExistsServlet）
1.获取前台传过来的username值，通过input[name=username]
2.将username传递给后台AccountExistsServlet并判断当前用户是否存在（前端把数据提交给后台通过json）
3.后台返回flag，判断好值是否存在给用户一个友好的提示
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%
String context = request.getContextPath();// /dt41_javaweb2
String path = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+context+"/";
%>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<base href="<%=path %>">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link type="text/css" rel="stylesheet" href="resources/css/style.css" />
<!--[if IE 6]>
<script src="resources/js/easybuy/iepng.js" type="text/javascript"></script>
<script type="text/javascript">
EvPNG.fix('div, ul, img, li, input, a');
</script>
<![endif]-->
<script type="text/javascript" src="resources/js/easybuy/jquery-1.11.1.min_044d0927.js"></script>
<script type="text/javascript" src="resources/js/easybuy/jquery.bxslider_e88acd1b.js"></script>
<script type="text/javascript" src="resources/js/easybuy/jquery-1.8.2.min.js"></script>
<script type="text/javascript" src="resources/js/easybuy/menu.js"></script>
<script type="text/javascript" src="resources/js/easybuy/select.js"></script>
<script type="text/javascript" src="resources/js/easybuy/lrscroll.js"></script>
<script type="text/javascript" src="resources/js/easybuy/iban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/fban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/f_ban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/mban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/bban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/hban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/tban.js"></script>
<script type="text/javascript" src="resources/js/easybuy/lrscroll_1.js"></script>
<title>尤洪</title>
</head>
<body>
<!--Begin Header Begin-->
<div class="soubg">
<div class="sou">
<span class="fr">
<span class="fl">你好，请<a href="<%=path %>/pages/front/Login.jsp">登录</a> <a href="<%=path %>/pages/front/Regist.jsp" style="color:#ff4e00;">免费注册</a> </span>
<span class="fl">| 关注我们：</span>
<span class="s_sh"><a href="#" class="sh1">新浪</a><a href="#" class="sh2">微信</a></span>
<span class="fr">| <a href="#">手机版 <img src="resources/images/s_tel.png" align="absmiddle" /></a></span>
</span>
</div>
</div>
<!--End Header End-->
<!--Begin Login Begin-->
<div class="log_bg">
<div class="top">
<div class="logo"><a href="Index.html"><img src="resources/images/logo.png" /></a></div>
</div>
<div class="regist">
<div class="log_img"><img src="resources/images/l_img.png" width="611" height="425" /></div>
<div class="reg_c">
<form>
<table border="0" style="width:420px; font-size:14px; margin-top:20px;" cellspacing="0" cellpadding="0">
<tr height="50" valign="top">
<td width="95"> </td>
<td>
<span class="fl" style="font-size:24px;">注册</span>
<span class="fr">已有商城账号，<a href="<%=path %>/pages/front/Login.jsp" style="color:#ff4e00;">我要登录</a></span>
</td>
</tr>
<tr height="50">
<td align="right"><font color="#ff4e00">*</font> 用户名 </td>
<td><input type="text" value="" class="l_user" name="username" placeholder="请输入2-12位数字字母下划线组合" pattern="\w{2,12}" required="required"/><span id="usernameTip"style="color:red "></span></td>
</tr>
<tr height="50">
<td align="right"><font color="#ff4e00">*</font> 密码 </td>
<td><input type="password" value="" class="l_pwd" /></td>
</tr>
<tr height="50">
<td align="right"><font color="#ff4e00">*</font> 确认密码 </td>
<td><input type="password" value="" class="l_pwd" /></td>
</tr>
<tr height="50">
<td align="right"><font color="#ff4e00">*</font> 邮箱 </td>
<td><input type="text" value="" class="l_email" /></td>
</tr>
<tr height="50">
<td align="right"><font color="#ff4e00">*</font> 手机 </td>
<td><input type="text" value="" class="l_tel" /></td>
</tr>
<tr height="50">
<td align="right"> <font color="#ff4e00">*</font> 验证码 </td>
<td>
<input type="text" value="" class="l_ipt" />
<a href="#" style="font-size:12px; font-family:'宋体';">换一张</a>
</td>
</tr>
<tr>
<td> </td>
<td style="font-size:12px; padding-top:20px;">
<span style="font-family:'宋体';" class="fl">
<label class="r_rad"><input type="checkbox" /></label><label class="r_txt">我已阅读并接受《用户协议》</label>
</span>
</td>
</tr>
<tr height="60">
<td> </td>
<td><input type="submit" value="立即注册" class="log_btn" /></td>
</tr>
</table>
</form>
</div>
</div>
</div>
<!--End Login End-->
<!--Begin Footer Begin-->
<div class="btmbg">
<div class="btm">
备案/许可证编号：蜀ICP备12009302号-1-www.dingguagua.com Copyright © 2015-2018 尤洪商城网 All Rights Reserved. 复制必究 , Technical Support: Dgg Group <br />
<img src="resources/images/b_1.gif" width="98" height="33" /><img src="resources/images/b_2.gif" width="98" height="33" /><img src="resources/images/b_3.gif" width="98" height="33" /><img src="resources/images/b_4.gif" width="98" height="33" /><img src="resources/images/b_5.gif" width="98" height="33" /><img src="resources/images/b_6.gif" width="98" height="33" />
</div>
</div>
<!--End Footer End -->
</body>
<script type="text/javascript">
$("input[name=username]").blur(function(){
//alert("哈哈");
//1、获取username的值
//var username=$("input[name=username]").val();
//2、将username传递给后台判断当前的用户名是否存在
//这里实现只能用ajax
$.ajax({//前端去请求servlet
url:'<%=path%>/AccountExistsServlet',
type:'post',
data:{
username:$("input[name=username]").val()
}, //前端把数据提交给后台通过json,注意ajax这里不需要添加双引号
dataType:'json',//是告诉ajax从Servlet中返回到jsp中ajax是什么数据类型
success:function(result){
var flag=result.flag;
//alert(flag);
if(flag){//用户名存在，则给用户一个友好的提示
$("#usernameTip").html("亲，此用户名已存在");
}else{
$("#usernameTip").html("");
}
}
});
});
</script>
<!--[if IE 6]>
<script src="//letskillie6.googlecode.com/svn/trunk/2/zh_CN.js"></script>
<![endif]-->
</html>
二、AccountExistsServlet
1.jsp调用servlet用的是doGet方法
2.servlet获取ajax（jsp中）传递过来的信息
3.接下来servlet会调用service业务方法，通过Boolean类型判断username是否存在。
4.然后判断完之后，**再通过json方式给ajax（即jsp）
response.getOutputStream().write(json.toString().getBytes(“utf-8”));**返回
且jsp通过ajax里的json方式接收数据，放到result里面
package cn.java.servlet;
import java.io.IOException;
import java.net.ResponseCache;
import java.sql.SQLException;
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 org.json.JSONObject;
import cn.java.service.UserService;
import cn.java.service.impl.UserServiceImpl;
/**
* Servlet implementation class AccountExistsServlet
*/
@WebServlet("/AccountExistsServlet")
public class AccountExistsServlet extends HttpServlet {
private UserService us=new UserServiceImpl();
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
//1、获取ajax传递过来的参数信息
String username=request.getParameter("username");
//2、调用业务方法，判断username是否存在着
boolean flag=us.isUserExists(username);
//3、 给ajax(Regist.jsp)返回数据（必须是json类型），把flag封装成json
JSONObject json=new JSONObject("{flag:"+flag+"}");//这里的json是个对象
response.getOutputStream().write(json.toString().getBytes("utf-8"));//如何把字符串变成字节数组
} catch (Exception e) {
e.printStackTrace();//try catch除了打印错误干不了别的，不能把错误解决掉
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
三、UserServiceImpl
1.写一个可以被AccountExistsServlet调用的Boolean类型的方法isUserExists（返回到servlet中是true或者false）
，然后在该方法中调用UserDaoImpl中的int类型的isUserExists方法
package cn.java.service.impl;
import java.sql.SQLException;
import java.util.Map;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.MapHandler;
import cn.java.dao.UserDao;
import cn.java.dao.impl.UserDaoImpl;
import cn.java.service.UserService;
import cn.java.utils.JdbcUtils;
public class UserServiceImpl implements UserService{
private UserDao ud=new UserDaoImpl();
//判断指定的用户是否已经存在
@Override
public boolean isUserExists(String username) throws SQLException{
int num=ud.isUserExists(username);
if(num>=1){
return true;
}
return false;
}
}
四、UserDaoImpl
1.dao层用来连接数据库，并且执行查询，然后结果是map类型的含num为整数的结果，然后通过Integer强制转换成int 类型，这样被service层调用容易判断
package cn.java.dao.impl;
import java.sql.SQLException;
import java.util.Map;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.MapHandler;
import cn.java.dao.UserDao;
import cn.java.utils.JdbcUtils;
public class UserDaoImpl implements UserDao {
private QueryRunner qr=new QueryRunner();
//判断指定的用户是否已经存在
/* (non-Javadoc)
* @see cn.java.dao.impl.UserDao#isUserExists(java.lang.String)
*/
@Override
public int isUserExists(String username) throws SQLException{
Map<String,Object> mp=qr.query(JdbcUtils.getConnection(),
"SELECT COUNT(*) AS num FROM `front_users` WHERE username='" + username + "'", new MapHandler());
return Integer.parseInt(mp.get("num")+"");
}
}
类似资料：