Servlet+JDBC实战开发书店项目讲解第四篇：登录实现

Servlet+JDBC 实战开发书店项目讲解第四篇：登录注册实现

在本篇博客中，我们将继续讲解 Servlet+JDBC 实战开发书店项目。这次我们将重点讲解如何实现登录和注册功能。

1. 创建数据库表

首先，我们需要在数据库中创建两个表，一个用于存储用户信息，另一个用于存储书籍信息。

CREATE TABLE users (id INT PRIMARY KEY AUTO_INCREMENT,username VARCHAR(50) NOT NULL,password VARCHAR(50) NOT NULL
);CREATE TABLE books (id INT PRIMARY KEY AUTO_INCREMENT,title VARCHAR(100) NOT NULL,author VARCHAR(100) NOT NULL,price DECIMAL(8,2) NOT NULL
);

2. 编写登录和注册页面

接下来，我们需要编写登录和注册页面的 HTML，让用户可以输入用户名和密码进行登录或注册操作。

login.html:

<!DOCTYPE html>
<html>
<head><title>Login</title>
</head>
<body><h2>Login</h2><form action="loginServlet" method="POST"><label for="username">Username:</label><input type="text" id="username" name="username" required><br><br><label for="password">Password:</label><input type="password" id="password" name="password" required><br><br><input type="submit" value="Login"></form>
</body>
</html>

register.html:

<!DOCTYPE html>
<html>
<head><title>Register</title>
</head>
<body><h2>Register</h2><form action="registerServlet" method="POST"><label for="username">Username:</label><input type="text" id="username" name="username" required><br><br><label for="password">Password:</label><input type="password" id="password" name="password" required><br><br><input type="submit" value="Register"></form>
</body>
</html>

3. 编写登录和注册 Servlet

然后，我们需要编写登录和注册的 Servlet，用于处理用户提交的表单数据，并将其保存到数据库中。

LoginServlet.java:

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class LoginServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String username = request.getParameter("username");String password = request.getParameter("password");// 进行用户名和密码的验证逻辑// ...// 假设验证逻辑通过，将用户信息保存到会话中request.getSession().setAttribute("username", username);response.setContentType("text/html");PrintWriter out = response.getWriter();out.println("Login Successful!");}
}

RegisterServlet.java:

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class RegisterServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String username = request.getParameter("username");String password = request.getParameter("password");// 进行用户名和密码的验证逻辑// ...// 假设验证逻辑通过，将用户信息保存到数据库中// ...response.setContentType("text/html");PrintWriter out = response.getWriter();out.println("Registration Successful!");}
}

4. Servlet开发

好的，以下是一个简单的用户登录功能的Servlet示例代码：

package com.example.blog.servlet;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.example.blog.db.UserDatabase;
import com.example.blog.models.User;public class LoginServlet extends HttpServlet {private UserDatabase userDatabase;@Overridepublic void init() throws ServletException {// 初始化数据库userDatabase = UserDatabase.getInstance();}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username = request.getParameter("username");String password = request.getParameter("password");// 检查用户名和密码是否正确if (userDatabase.isValidUser(new User(username, password))) {// 登录成功request.getSession().setAttribute("username", username);response.sendRedirect("home.jsp");  // 重定向到首页或其他需要登录后访问的页面} else {// 登录失败response.sendRedirect("login.jsp?error=true");  // 重定向到登录页面，并传递错误参数}}
}