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  • 最简单的Servlet继承HttpServlet查询数据库登录验证

    <%--
      Created by IntelliJ IDEA.
      User: yunqing
      Date: 2017-12-06
      Time: 9:11
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
      <head>
        <title>login</title>
      </head>
      <body>
          <form action="/LoginFromMysql" method="post">
            用户名:<input type="text" name="username">
            密码:<input type="password" name="password">
            <input type="submit" value="submit">
          </form>
    
      </body>
    </html>

    web.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
             version="3.1">
        <!-- 从数据库查询登录-->
        <servlet>
            <servlet-name>fromMysql</servlet-name>
            <servlet-class>com.yunqing.servlet.LoginFromMysql</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>fromMysql</servlet-name>
            <url-pattern>/LoginFromMysql</url-pattern>
        </servlet-mapping>
    </web-app>

    LoginFromMysql.java

    package com.yunqing.servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.sql.*;
    
    public class LoginFromMysql extends HttpServlet {
    
        public static final String url = "jdbc:mysql://localhost:3306/mybatis";
        public static final String name = "root";
        public static final String pass = "5678";
    
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         //获取前端表单中的数据 String username
    = req.getParameter("username"); String password = req.getParameter("password"); try { //需要添加mysql-connector-java-xxx-bin.jar(在idea中需要把jar包放到TomCAT的lib目录中) Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection(url,name,pass); String sql = "SELECT COUNT(id) FROM t_user t WHERE t.name = ? AND t.gender = ?"; ps = conn.prepareStatement(sql); ps.setString(1,username); ps.setString(2,password); rs = ps.executeQuery(); while (rs.next()) { int count = rs.getInt(1); if (count > 0) { resp.getWriter().print("Success=" + username); } else { resp.getWriter().print("Error=" + username + "BCZ"); } } } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } finally { try { if (rs != null) { rs.close(); } if (ps != null) { ps.close(); } if (conn != null) { conn.close(); } } catch (SQLException e) { e.printStackTrace(); } } } }
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  • 原文地址:https://www.cnblogs.com/yunqing/p/8026326.html
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