Database table structure:
The table has a record:
Project Structure:
Register. jsp
<% @ 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>Checkservlet. Java
package com.xu.servlets;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 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 = "org.gjt.mm.mysql.Driver";public static final String DBURL = "jdbc:mysql://localhost:3306/mydb";public static final String DBUSER = "root";public static final String DBPASS = "root";private static final long serialVersionUID = 7502494116656742257L;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("utf-8");response.setContentType("text/html");Connection conn = null;PreparedStatement pstmt = null;ResultSet rs = null;PrintWriter out = response.getWriter();String userid = request.getParameter("userid");try{Class.forName(DBDRIVER);conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS);String sql = "SELECT COUNT(userid) FROM user WHERE userid = ?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, userid);rs = pstmt.executeQuery();if(rs.next()){if(rs.getInt(1)>0){out.print("true");}else{out.print("false");}}out.close();}catch (Exception e) {e.printStackTrace();}finally{try{conn.close();}catch (Exception e) {e.printStackTrace();}}}}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> <servlet> <description>This is the description of my J2EE component</description> <display-name>This is the display name of my J2EE component</display-name> <servlet-name>CheckServlet</servlet-name> <servlet-class>com.xu.servlets.CheckServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CheckServlet</servlet-name> <url-pattern>/CheckServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list></web-app>Running result:
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