JavaWeb开发 : tomcat+Servlet+JSP

tomcat+Servlet+JSP

现在已经不是主流了,可以学习一下,了解springboot框架的原理(悲,为什么要学过时的老东西)

不过可能在维护老应用时可能用到,小型项目也是一个不错的选择

教程视频

https://www.bilibili.com/video/BV1Sm4y1d76Q?spm_id_from=333.788.videopod.episodes\&vd_source=837d4fe54a9ceb585673b377f66d35cb

tomcat

因为使用的java8,只能选用tomcat9 下载.zip文件后解压

创建环境变量,新建CATALINA_HOME值为D:\development\apache-tomcat-9.0.97

然后在path中添加%CATALINA_HOME%\bin

然后浏览器输入 localhost:8080

新建项目

基于idea2022,新建jakarta ee 模板选择web application,应用程序服务器选择安装的tomcat版本,下一步,选择版本java ee 8

src/main/webapp/index.jsp就是我们启动的首页文件

然后我们编辑配置,添加配置,选择tomcat 本地

部署中添加工程目录

就可以运行了,注意要关闭之前启动的tomcat命令行,不然会端口占用,导致运行失败

Model

模型层,封装对象,让操作逻辑更加清晰

package model;

public class User {
    private int userId;
    private String username;
    private String password;  // 保存加密后的密码
    private String salt;      // 保存盐

    // 构造函数
    public User(int userId, String username, String password, String salt) {
        this.userId = userId;
        this.username = username;
        this.password = password;
        this.salt = salt;
    }

    // 获取用户ID
    public int getUserId() {
        return userId;
    }

    // 获取用户名
    public String getUsername() {
        return username;
    }
}

Mysql

先创建数据库javaweb

连接数据库

package db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class Database {
    private static final String URL = "jdbc:mysql://localhost:3306/javaweb?useUnicode=true&characterEncoding=UTF-8";
    private static final String USER = "root";
    private static final String PASSWORD = "root";

    public static Connection getConnection() throws SQLException {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            System.out.println("Database connected");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return DriverManager.getConnection(URL, USER, PASSWORD);
    }
}

DAO

DAO（Data Access Object） 是一种常用的设计模式，旨在将应用程序的业务逻辑与数据访问逻辑分离，从而提高代码的可维护性、可扩展性和测试性。

使用model层,将sql语句封装,提供接口给servlet

package db;

import model.User;

import java.security.MessageDigest;
import java.security.SecureRandom;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Base64;

public class UserDAO {

    // 检查用户名是否已存在
    public boolean isUsernameExists(String username) {
        String sql = "SELECT COUNT(*) FROM users WHERE username = ?";
        try (Connection conn = Database.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, username);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                return rs.getInt(1) > 0;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    // 注册用户
    public boolean registerUser(String username, String password) {
        if (isUsernameExists(username)) {
            System.out.println("username already exists！");
            return false;
        }

        // 生成盐并加密密码
        String salt = generateSalt();
        String encryptedPassword = encryptPassword(password, salt);

        String sql = "INSERT INTO users (username, password, salt) VALUES (?, ?, ?)";
        try (Connection conn = Database.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, username);
            stmt.setString(2, encryptedPassword); // 只存储加密后的密码
            stmt.setString(3, salt); // 单独存储盐
            int rowsInserted = stmt.executeUpdate();
            return rowsInserted > 0;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    // 用户登录
    public User loginUser(String username, String password) {
        String sql = "SELECT user_id, password, salt FROM users WHERE username = ?";
        try (Connection conn = Database.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, username);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                int userId = rs.getInt("user_id");
                String storedEncryptedPassword = rs.getString("password");
                String salt = rs.getString("salt");

                if (storedEncryptedPassword.equals(encryptPassword(password, salt))) {
                    System.out.println("login success!");
                    // 返回一个 User 对象，包含用户ID、用户名、盐和密码
                    return new User(userId, username, storedEncryptedPassword, salt);
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        System.out.println("username or password incorrect！");
        return null; // 登录失败返回 null
    }

    // 加密密码
    private String encryptPassword(String password, String salt) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            md.update(salt.getBytes()); // 使用盐加密密码
            byte[] hashedPassword = md.digest(password.getBytes());
            return Base64.getEncoder().encodeToString(hashedPassword);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    // 生成盐
    private String generateSalt() {
        SecureRandom random = new SecureRandom();
        byte[] salt = new byte[16];
        random.nextBytes(salt);
        return Base64.getEncoder().encodeToString(salt);
    }
}

Servlet

ServLet = Server+Applet(小程序) ,一种在服务器端运行的小程序,用于处理来自jsp的请求,通过DAO操控数据库给出响应

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=UTF-8");
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");

        int id = Integer.parseInt(req.getParameter("id"));
        String password = req.getParameter("pwd");

        PrintWriter out = resp.getWriter();
        out.println("账号"+id+"密码"+ password);

    }
}

Jsp

Jsp = JavaServer Pages,用于绘制可视化界面

html的绘制

<%@ page contentType="text/html; charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录页面</title>
    <link rel="stylesheet" type="text/css" href="styles/style.css">
</head>
<body>
<div class="container">
    <h2>登录页面</h2>

    <!-- 登录表单 -->
    <form action="login" method="POST">
        <label for="username">用户名:</label>
        <input type="text" id="username" name="username" required/>

        <label for="password">密码:</label>
        <input type="password" id="password" name="password" required/>

        <input type="submit" value="登录"/>
        <a href="register.jsp" class="button">注册</a>

    </form>
</div>
</body>
</html>

css的封装

body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f9;
    color: #333;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

.container {
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    max-width: 400px;
    width: 100%;
    text-align: center;
}

h2 {
    margin-bottom: 20px;
    color: #2c3e50;
}

label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}

input[type="text"],
input[type="password"] {
    width: 100%;
    padding: 10px;
    margin-bottom: 15px;
    border: 1px solid #ddd;
    border-radius: 4px;
}

input[type="submit"],
.button {
    background-color: #3498db;
    color: white;
    border: none;
    padding: 10px 15px;
    border-radius: 4px;
    cursor: pointer;
    text-transform: uppercase;
    font-size: 14px;
}

input[type="submit"]:hover,
.button:hover {
    background-color: #2980b9;
}