JSP+Servlet+JavaBean实现数据库的增删改查代码

好的，以下是JSP+Servlet+JavaBean实现数据库的增删改查的代码示例：

1. JavaBean类

public class User {
    private int id;
    private String name;
    private int age;
    private String gender;

    // 构造方法
    public User() {}

    // setter和getter方法
    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getAge() {
        return age;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getGender() {
        return gender;
    }
}

2. DAO层

public class UserDAO {
    // 数据库连接信息
    private String url = "jdbc:mysql://localhost:3306/test";
    private String username = "root";
    private String password = "123456";

    // 增加用户
    public void addUser(User user) {
        try {
            // 加载MySQL驱动程序
            Class.forName("com.mysql.jdbc.Driver");
            // 获取数据库连接
            Connection conn = DriverManager.getConnection(url, username, password);
            // 创建PreparedStatement对象
            PreparedStatement ps = conn.prepareStatement("INSERT INTO user(name, age, gender) VALUES (?, ?, ?)");
            // 设置参数
            ps.setString(1, user.getName());
            ps.setInt(2, user.getAge());
            ps.setString(3, user.getGender());
            // 执行SQL语句
            ps.executeUpdate();
            // 关闭连接和PreparedStatement对象
            ps.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 删除用户
    public void deleteUser(int id) {
        try {
            // 加载MySQL驱动程序
            Class.forName("com.mysql.jdbc.Driver");
            // 获取数据库连接
            Connection conn = DriverManager.getConnection(url, username, password);
            // 创建PreparedStatement对象
            PreparedStatement ps = conn.prepareStatement("DELETE FROM user WHERE id=?");
            // 设置参数
            ps.setInt(1, id);
            // 执行SQL语句
            ps.executeUpdate();
            // 关闭连接和PreparedStatement对象
            ps.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 修改用户
    public void updateUser(User user) {
        try {
            // 加载MySQL驱动程序
            Class.forName("com.mysql.jdbc.Driver");
            // 获取数据库连接
            Connection conn = DriverManager.getConnection(url, username, password);
            // 创建PreparedStatement对象
            PreparedStatement ps = conn.prepareStatement("UPDATE user SET name=?, age=?, gender=? WHERE id=?");
            // 设置参数
            ps.setString(1, user.getName());
            ps.setInt(2, user.getAge());
            ps.setString(3, user.getGender());
            ps.setInt(4, user.getId());
            // 执行SQL语句
            ps.executeUpdate();
            // 关闭连接和PreparedStatement对象
            ps.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 查询用户
    public List<User> getUsers() {
        List<User> userList = new ArrayList<>();
        try {
            // 加载MySQL驱动程序
            Class.forName("com.mysql.jdbc.Driver");
            // 获取数据库连接
            Connection conn = DriverManager.getConnection(url, username, password);
            // 创建Statement对象
            Statement stmt = conn.createStatement();
            // 执行SQL语句
            ResultSet rs = stmt.executeQuery("SELECT * FROM user");
            // 处理结果集
            while (rs.next()) {
                User user = new User();
                user.setId(rs.getInt("id"));
                user.setName(rs.getString("name"));
                user.setAge(rs.getInt("age"));
                user.setGender(rs.getString("gender"));
                userList.add(user);
            }
            // 关闭连接和Statement对象
            rs.close();
            stmt.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return userList;
    }
}

3. Servlet类

public class UserServlet extends HttpServlet {
    // 创建UserDAO对象
    private UserDAO userDao = new UserDAO();

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理GET请求
        List<User> userList = userDao.getUsers();
        // 将userList存入request对象中
        request.setAttribute("userList", userList);
        // 转发到user.jsp页面
        RequestDispatcher rd = request.getRequestDispatcher("user.jsp");
        rd.forward(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理POST请求
        String action = request.getParameter("action");
        if ("add".equals(action)) {
            // 添加用户
            User user = new User();
            user.setName(request.getParameter("name"));
            user.setAge(Integer.parseInt(request.getParameter("age")));
            user.setGender(request.getParameter("gender"));
            userDao.addUser(user);
        } else if ("delete".equals(action)) {
            // 删除用户
            int id = Integer.parseInt(request.getParameter("id"));
            userDao.deleteUser(id);
        } else if ("update".equals(action)) {
            // 修改用户
            User user = new User();
            user.setId(Integer.parseInt(request.getParameter("id")));
            user.setName(request.getParameter("name"));
            user.setAge(Integer.parseInt(request.getParameter("age")));
            user.setGender(request.getParameter("gender"));
            userDao.updateUser(user);
        }
        // 重定向到UserServlet，处理GET请求
        response.sendRedirect(request.getContextPath() + "/UserServlet");
    }
}

4. JSP页面

<html>
<head>
    <title>用户管理</title>
</head>
<body>
    <h1>用户管理</h1>
    <table border="1">
        <thead>
            <tr>
                <th>ID</th>
                <th>姓名</th>
                <th>年龄</th>
                <th>性别</th>
                <th>操作</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach items="${userList}" var="user">
                <tr>
                    <td>${user.id}</td>
                    <td>${user.name}</td>
                    <td>${user.age}</td>
                    <td>${user.gender}</td>
                    <td>
                        <form method="post" action="UserServlet">
                            <input type="hidden" name="id" value="${user.id}">
                            <input type="hidden" name="action" value="delete">
                            <input type="submit" value="删除">
                        </form>
                        <form method="post" action="UserServlet">
                            <input type="hidden" name="id" value="${user.id}">
                            <input type="hidden" name="action" value="update">
                            <input type="submit" value="修改">
                        </form>
                    </td>
                </tr>
            </c:forEach>
        </tbody>
    </table>
    <hr>
    <h2>添加用户</h2>
    <form method="post" action="UserServlet">
        姓名：<input type="text" name="name"><br>
        年龄：<input type="text" name="age"><br>
        性别：<input type="text" name="gender"><br>
        <input type="hidden" name="action" value="add">
        <input type="submit" value="添加">
    </form>
</body>
</html>

以上代码仅为示例，具体实现还需要根据具体需求进行调整。