AJAX is used to determine whether the user is registered-JS Tutorial-php.cn

This article mainly introduces AJAX in detail to determine whether the user is registered, which has certain reference value. Interested friends can refer to it

On many registration pages, we may We will encounter the following situations. When we register a user name, we may be prompted that the user name has been registered. The implementation is to apply AJAX technology.

First write a login page

    
   用户ID 
 姓名：
 密码：

Copy after login

Then write a servlet Java code

import java.io.IOException; import java.io.PrintWriter; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CheckServlet extends HttpServlet{ public static final String DBDRIVER = "oracle.jdbc.OracleDriver"; public static final String DBURL = "jdbc:oracle:thin:@59.173.240.149:1521:heer"; public static final String DBUSER = "hnsyu_dev"; public static final String DBPASS = "hnsyuok"; public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ this.doPost(request, response); } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ request.setCharacterEncoding("gbk"); response.setContentType("text/html"); Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; PrintWriter out = response.getWriter(); String userid = request.getParameter("userid"); try { Class.forName(DBDRIVER); connection = DriverManager.getConnection(DBURL, DBUSER, DBPASS); String sql = "select count(userid) from userdemo where userid=?"; preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1,userid); resultSet = preparedStatement.executeQuery(); if (resultSet.next()) { if(resultSet.getInt(1)>0){ out.print("false"); System.out.println("true"); }else { out.print("false"); } } out.close(); } catch (Exception e) { e.printStackTrace(); }finally{ try { connection.close(); } catch (Exception e) { e.printStackTrace(); } } } }

Copy after login

You also need to configure it in web.xml

    index.jsp   CheckServlet CheckServlet   CheckServlet /CheckServlet

Copy after login

The above I compiled it for everyone. I hope it will be helpful to everyone in the future.

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