JDBC+三层结构+jsp简单案例

好的，下面是一个简单的JDBC+三层结构+jsp的示例：

1. 创建数据库表

首先，我们创建一个名为“user”的表，包含id、username和password三个字段。

2. 编写JavaBean层

在JavaBean层，我们定义一个User类，包含id、username和password三个属性，以及相应的getter和setter方法。

public class User {
    private int id;
    private String username;
    private String password;
    
    // getter and setter methods
}

3. 编写DAO层

在DAO层，我们使用JDBC连接数据库，并编写相应的增删改查方法。

public class UserDao {
    // JDBC连接参数
    private String url = "jdbc:mysql://localhost:3306/test";
    private String username = "root";
    private String password = "root";
    
    // 查询用户信息
    public User getUserById(int id) {
        User user = null;
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
            String sql = "SELECT * FROM user WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            rs = pstmt.executeQuery();
            if (rs.next()) {
                user = new User();
                user.setId(rs.getInt("id"));
                user.setUsername(rs.getString("username"));
                user.setPassword(rs.getString("password"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return user;
    }
    
    // 添加用户信息
    public int addUser(User user) {
        int result = 0;
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
            String sql = "INSERT INTO user(username, password) VALUES (?, ?)";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            result = pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }
    
    // 更新用户信息
    public int updateUser(User user) {
        int result = 0;
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
            String sql = "UPDATE user SET username = ?, password = ? WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            pstmt.setInt(3, user.getId());
            result = pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }
    
    // 删除用户信息
    public int deleteUser(int id) {
        int result = 0;
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
            String sql = "DELETE FROM user WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            result = pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }
}

4. 编写Service层

在Service层，我们调用DAO层的方法，并进行相应的业务逻辑处理。

public class UserService {
    private UserDao userDao = new UserDao();
    
    // 获取用户信息
    public User getUserById(int id) {
        return userDao.getUserById(id);
    }
    
    // 添加用户信息
    public int addUser(User user) {
        return userDao.addUser(user);
    }
    
    // 更新用户信息
    public int updateUser(User user) {
        return userDao.updateUser(user);
    }
    
    // 删除用户信息
    public int deleteUser(int id) {
        return userDao.deleteUser(id);
    }
}

5. 编写Controller层

在Controller层，我们通过JSP页面获取用户输入的数据，并调用Service层的方法进行相应的操作。

public class UserController extends HttpServlet {
    private UserService userService = new UserService();
    
    // 处理GET请求
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    
    // 处理POST请求
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 设置字符编码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        
        // 获取操作类型
        String action = request.getParameter("action");
        if ("add".equals(action)) {
            // 添加用户信息
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            User user = new User();
            user.setUsername(username);
            user.setPassword(password);
            int result = userService.addUser(user);
            if (result > 0) {
                response.sendRedirect("list.jsp");
            } else {
                response.getWriter().println("添加用户信息失败！");
            }
        } else if ("delete".equals(action)) {
            // 删除用户信息
            int id = Integer.parseInt(request.getParameter("id"));
            int result = userService.deleteUser(id);
            if (result > 0) {
                response.sendRedirect("list.jsp");
            } else {
                response.getWriter().println("删除用户信息失败！");
            }
        } else if ("update".equals(action)) {
            // 更新用户信息
            int id = Integer.parseInt(request.getParameter("id"));
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            User user = new User();
            user.setId(id);
            user.setUsername(username);
            user.setPassword(password);
            int result = userService.updateUser(user);
            if (result > 0) {
                response.sendRedirect("list.jsp");
            } else {
                response.getWriter().println("更新用户信息失败！");
            }
        }
    }
}

6. 编写JSP页面

最后，在JSP页面上展示用户信息，并提供相应的操作。

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>用户信息列表</title>
</head>
<body>
    <h1>用户信息列表</h1>
    <table border="1">
        <thead>
            <tr>
                <th>ID</th>
                <th>用户名</th>
                <th>密码</th>
                <th>操作</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach var="user" items="${users}">
                <tr>
                    <td>${user.id}</td>
                    <td>${user.username}</td>
                    <td>${user.password}</td>
                    <td>
                        <a href="delete.jsp?id=${user.id}&action=delete">删除</a>
                        <a href="update.jsp?id=${user.id}&username=${user.username}&password=${user.password}&action=update">修改</a>
                    </td>
                </tr>
            </c:forEach>
        </tbody>
    </table>
    <hr>
    <h1>添加用户信息</h1>
    <form action="UserController" method="post">
        <input type="hidden" name="action" value="add">
        <p>用户名：<input type="text" name="username"></p>
        <p>密码：<input type="password" name="password"></p>
        <p><input type="submit" value="添加"></p>
    </form>
</body>
</html>

以上就是一个简单的JDBC+三层结构+jsp的案例，其中采用了MVC的设计模式，将业务逻辑、数据访问和表示分离开来，使代码更加清晰和易于维护。