AJAX实现注册验证用户名

admin

功能说明
       当用户在注册页面输入用户名并且鼠标焦点离开输入框时，到数据表中去验证该用户名是否已经存在，如果存在提示不可用，否则，提示可用。
接口

复制代码
public interface UserDao {
 public User findName(String name);
}

接口实现类
' x+ H' j' b" R1 V# v3 H

复制代码
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDaoImpl implements UserDao {

 @Override
 public User findName(String name) {
  User user =null;
  Connection conn = DBHelper.getConn();
  String sql = "select * from user where name=?";
  try {
   PreparedStatement ps = conn.prepareStatement(sql);
   ps.setString(1,name);
   ResultSet rs = ps.executeQuery();
   if (rs.next()){
    user = new User();
    user.setId(rs.getInt(1));
    user.setName(rs.getString(2));
    user.setPassword(rs.getString(3));
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return user;
 }
}

servlet
' R& M. t0 [4 }  e% y

复制代码
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 java.io.IOException;

@WebServlet("/findName")
public class FindNameServlet extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  request.setCharacterEncoding("utf-8");
  response.setContentType("text/html;charset=utf-8");
  String name = request.getParameter("name");
  UserDao userDao = new UserDaoImpl();
  User name1 = userDao.findName(name);
  if (name1!=null){
   response.getWriter().write("1");
  }else {
   response.getWriter().write("2");
  }
 }

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

JSP页面

复制代码
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
 <head>
 <title>AJAX实际操作注册验证用户名</title>
 <script src="js/jquery-1.8.3.js"></script>
 </head>
 <body>
 <form action="#" method="post">
 <script type="text/javascript">
  $(function () {
   $("[name=userName]").blur(function () {
    $.ajax({
     type:"get",
     url:"findName?name="+$("[name=userName]").val(),
     dataType:"text",
     success:function (data) {
      //alert(data);
      if (data=="1"){
       $("#show").html("用户已存在！！！")
      }else {
       $("#show").html("用户名可用")
      }
     }
    })
   })
  });
 </script>
 账号<input type="text" name="userName"><span id="show"></span></br>
 密码<input type="password" name="password"></br>
 <input type="submit" value="提交">
 </form>
 </body>
</html>

数据库如下：

运行结果如下：
2 B( V2 t; |6 m% L
) F2 k3 C3 R- ?  Y$ r) ?