HttpServlet练习

在MySQL数据库中创建一个test_users数据表，添加3个字段：id，user，password。并录入几条记录。

定义一个login.html,里边定义两个请求字段：user，password。发送请求到loginServlet

在创建一个LoginServlet(需要继承自HttpServlet，并重写其doPost方法)，

在其中获取请求的user，password

利用JDBC从test_users中查询有没有和页面输入的user，password对应的记录

若有，响应Hello：xxx，若没有，响应Sorry：xxx 　　xxx为user。

数据库：

HttpServlet练习

JSP：

<%--
  Created by IntelliJ IDEA.
  User: dell
  Date: 2019/5/26
  Time: 17:08
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<form action="LoginServlet1" method="POST">
    姓名：<input type="text" name="username">
    密码：<input type="password" name="password">
    <input type="submit" value="submit">
</form>
</body>
</html>

HttpServlet：

package com.demo.javaweb;

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.io.PrintWriter;
import java.sql.*;

public class LoginServlet1 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        String sql = "select count(id) from test_users where user=? and password=?";

        Connection conn = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/yang?serverTimezone=UTC";
            String user = "root";
            String password1 = "password";
            conn = DriverManager.getConnection(url,user,password1);

            preparedStatement = conn.prepareStatement(sql);
            preparedStatement.setString(1,username);
            preparedStatement.setString(2,password);

            resultSet = preparedStatement.executeQuery();
            PrintWriter printWriter = resp.getWriter();
            if (resultSet.next()){
                int count = resultSet.getInt(1);
                if (count>0){
                    printWriter.print("Hello!    "+ username);
                }else{
                    printWriter.print("Sorry   " + username);
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (resultSet!=null){
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (preparedStatement!=null){
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

    }
}

Web.xml

    <servlet>
        <servlet-name>LoginServlet1</servlet-name>
        <servlet-class>com.demo.javaweb.LoginServlet1</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet1</servlet-name>
        <url-pattern>/LoginServlet1</url-pattern>
    </servlet-mapping>

运行：

HttpServlet练习

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