AJAX is used to determine whether a user is registered. ajax is used to determine whether a user is registered.
On many registration pages, we may encounter the following situations. When registering a user name, we may prompt that the user name has been registered. The implementation is to apply AJAX technology.
First, write a login page.
<Html>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();}}}}You also need to configure in web. xml
<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name></display-name> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>CheckServlet</servlet-name> <servlet-class>CheckServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CheckServlet</servlet-name> <url-pattern>/CheckServlet</url-pattern> </servlet-mapping> </web-app>The above is all the content of this article. I hope it will be helpful for your learning and support for helping customers.
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