在java Web中如何用Ajax实现用户名已存在

答案：数据库操作类(mysql数据库)
1.import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class BaseDao{
 protected Connection conn;
 protected Statement sta;
 protected ResultSet rs;
 protected PreparedStatement ps;
 
 public void setConnection(){
  try {
   Class.forName("com.mysql.jdbc.Driver");
   String url = "jdbc:mysql://localhost:3306/dianlv";
   conn = DriverManager.getConnection(url,"root","root");
  } catch (ClassNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
 public void closeAll(){
  try{
   
   if(rs!=null){
    rs.close();
   }if(ps!=null){
    ps.close();
   }if(sta!=null){
    sta.close();
   }if(conn!=null){
    conn.close();
   }
   
  }catch(SQLException e){
   e.printStackTrace();
  }
 }
}
2.UserDao类集成baseDao类，实现对数据库中的数据名字超找：
import java.sql.SQLException;
public class UserDao extends BaseDao {
 
 /**
  * 验证用户名是否成功；如果成功了返回true；
  * 
  * **/
 public boolean checkUserName(String userName){
  boolean flag = false;
  this.setConnection();
  String sql ="select * from users where userName = ?";
  
  try {
   ps = conn.prepareStatement(sql);
   ps.setString(1,userName);
   rs = ps.executeQuery();
   if(rs.next()){
    
    flag = true;
   }
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  
  
  
  return flag;
 }
3.上面代码实现应该有一个user实体：创建user实体类：
public class User {
 private String userName;
 private int id;
 private String password;
 public String getUserName() {
  return userName;
 }
 public void setUserName(String userName) {
  this.userName = userName;
 }
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public String getPassword() {
  return password;
 }
 public void setPassword(String password) {
  this.password = password;
 }
}
4.写一个servlet用户验证用户名是否重复;
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.fz.dao.UserDao;
public class CheckUserNameServlet extends HttpServlet {
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  doPost(request, response);
 }
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  request.setCharacterEncoding("utf-8");
  
  response.setContentType("text/html;charset=utf-8"); 
5:jsp页面用于用户的操作，上面用到ajax技术用户验证用户名是否重复
<%@ 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=>    
    <title>My JSP 'Login.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/jquery-1.7.1.min.js"></script>
 <script type="text/javascript">
  function checkUnique(){
    var content = $('#userName').val(); //获取文本框中输入的内容
    var url = 'servlet/CheckUserNameServlet';
    
    $.post(
     url, //处理请求的url
     {'name':content}, //传递的参数
     function(data){ //请求处理完毕之后的回调函数
      if(data == 'true'){//返回的是字符串不能用data = false这样比较
       $("#s1").text("用户名不唯一");```````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````
      }else if(data == 'false'){
       $("#s1").text("用户名可用");
      }
      
     }
    );
   }
 
 
 </script>
  </head>
  
  <body>
    <% request.setCharacterEncoding("utf-8"); 
     
    %>
    
    <form action="">
     用户名：<input  type="text" name="uerName" onblur="checkUnique();" id = "userName"/>  <span id="s1"></span><br/>
     密码：<input type="pas
上一个：怎样将这个JAVA程序的变量改成不用static修饰？
下一个：初学JAVA，几个不懂的问题
更多图片编程知识: