利用servlet+jsp+javabean设计一个系统实现增删改查

好的，这是一个比较常见的 Java Web 项目需求，下面我会给出一个简单的实现方式。

1. 前置条件

在开始实现之前，需要确保你已经安装好了 Java 开发环境、Tomcat 服务器和 MySQL 数据库，并且能够使用这些工具进行开发。

2. 创建数据库

首先，需要创建一个数据库和表来存储数据。我们创建一个名为 `user` 的数据库，并在其中创建一个名为 `user_info` 的表，表结构如下：

CREATE TABLE `user_info` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `gender` varchar(10) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

3. 创建 JavaBean

在 `src` 目录下创建一个名为 `User.java` 的 JavaBean，用于表示用户信息：

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

    // getter 和 setter 方法
}

4. 创建 Dao 类

在 `src` 目录下创建一个名为 `UserDao.java` 的类，用于实现对用户信息的增删改查操作。这里我们使用 JDBC 来访问 MySQL 数据库：

public class UserDao {
    private Connection conn;

    public UserDao() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/user";
            String username = "root";
            String password = "root";
            conn = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public List<User> getAllUsers() {
        List<User> userList = new ArrayList<>();
        try {
            String sql = "SELECT * FROM user_info";
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();
            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);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return userList;
    }

    public User getUserById(int id) {
        User user = null;
        try {
            String sql = "SELECT * FROM user_info WHERE id=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                user = new User();
                user.setId(rs.getInt("id"));
                user.setName(rs.getString("name"));
                user.setAge(rs.getInt("age"));
                user.setGender(rs.getString("gender"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return user;
    }

    public void addUser(User user) {
        try {
            String sql = "INSERT INTO user_info(name, age, gender) VALUES (?, ?, ?)";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, user.getName());
            ps.setInt(2, user.getAge());
            ps.setString(3, user.getGender());
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void updateUser(User user) {
        try {
            String sql = "UPDATE user_info SET name=?, age=?, gender=? WHERE id=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, user.getName());
            ps.setInt(2, user.getAge());
            ps.setString(3, user.getGender());
            ps.setInt(4, user.getId());
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void deleteUser(int id) {
        try {
            String sql = "DELETE FROM user_info WHERE id=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

5. 创建 Servlet 类

在 `src` 目录下创建一个名为 `UserServlet.java` 的 Servlet 类，用于处理用户请求。这里我们使用 `doGet` 和 `doPost` 方法来处理 GET 和 POST 请求：

public class UserServlet extends HttpServlet {
    private UserDao userDao;

    public void init() throws ServletException {
        userDao = new UserDao();
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if (action == null) {
            action = "list";
        }
        switch (action) {
            case "list":
                listUsers(request, response);
                break;
            case "view":
                viewUser(request, response);
                break;
            case "add":
                addUser(request, response);
                break;
            case "edit":
                editUser(request, response);
                break;
            case "delete":
                deleteUser(request, response);
                break;
            default:
                listUsers(request, response);
                break;
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    private void listUsers(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<User> userList = userDao.getAllUsers();
        request.setAttribute("userList", userList);
        request.getRequestDispatcher("list.jsp").forward(request, response);
    }

    private void viewUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        User user = userDao.getUserById(id);
        request.setAttribute("user", user);
        request.getRequestDispatcher("view.jsp").forward(request, response);
    }

    private void addUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String gender = request.getParameter("gender");
        User user = new User();
        user.setName(name);
        user.setAge(age);
        user.setGender(gender);
        userDao.addUser(user);
        response.sendRedirect("UserServlet");
    }

    private void editUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        User user = userDao.getUserById(id);
        request.setAttribute("user", user);
        request.getRequestDispatcher("edit.jsp").forward(request, response);
    }

    private void updateUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String gender = request.getParameter("gender");
        User user = new User();
        user.setId(id);
        user.setName(name);
        user.setAge(age);
        user.setGender(gender);
        userDao.updateUser(user);
        response.sendRedirect("UserServlet");
    }

    private void deleteUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        userDao.deleteUser(id);
        response.sendRedirect("UserServlet");
    }
}

6. 创建 JSP 页面

在 `WebContent` 目录下创建以下 JSP 页面：

- `list.jsp`：显示用户列表

<%@ 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>User List</title>
</head>
<body>
    <h1>User List</h1>
    <table>
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Age</th>
            <th>Gender</th>
            <th>Action</th>
        </tr>
        <c:forEach items="${userList}" var="user">
            <tr>
                <td>${user.id}</td>
                <td>${user.name}</td>
                <td>${user.age}</td>
                <td>${user.gender}</td>
                <td>
                    <a href="UserServlet?action=view&id=${user.id}">View</a>
                    <a href="UserServlet?action=edit&id=${user.id}">Edit</a>
                    <a href="UserServlet?action=delete&id=${user.id}">Delete</a>
                </td>
            </tr>
        </c:forEach>
    </table>
    <br>
    <a href="UserServlet?action=add">Add User</a>
</body>
</html>

- `view.jsp`：显示单个用户信息

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>User View</title>
</head>
<body>
    <h1>User View</h1>
    <table>
        <tr>
            <td>ID:</td>
            <td>${user.id}</td>
        </tr>
        <tr>
            <td>Name:</td>
            <td>${user.name}</td>
        </tr>
        <tr>
            <td>Age:</td>
            <td>${user.age}</td>
        </tr>
        <tr>
            <td>Gender:</td>
            <td>${user.gender}</td>
        </tr>
    </table>
    <br>
    <a href="UserServlet">Back to List</a>
</body>
</html>

- `add.jsp`：添加用户表单

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Add User</title>
</head>
<body>
    <h1>Add User</h1>
    <form action="UserServlet" method="post">
        <input type="hidden" name="action" value="add">
        <table>
            <tr>
                <td>Name:</td>
                <td><input type="text" name="name"></td>
            </tr>
            <tr>
                <td>Age:</td>
                <td><input type="text" name="age"></td>
            </tr>
            <tr>
                <td>Gender:</td>
                <td>
                    <input type="radio" name="gender" value="Male">Male
                    <input type="radio" name="gender" value="Female">Female
                </td>
            </tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Add"></td>
            </tr>
        </table>
    </form>
    <br>
    <a href="UserServlet">Back to List</a>
</body>
</html>

- `edit.jsp`：编辑用户表单

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Edit User</title>
</head>
<body>
    <h1>Edit User</h1>
    <form action="UserServlet" method="post">
        <input type="hidden" name="action" value="edit">
        <input type="hidden" name="id" value="${user.id}">
        <table>
            <tr>
                <td>Name:</td>
                <td><input type="text" name="name" value="${user.name}"></td>
            </tr>
            <tr>
                <td>Age:</td>
                <td><input type="text" name="age" value="${user.age}"></td>
            </tr>
            <tr>
                <td>Gender:</td>
                <td>
                    <input type="radio" name="gender" value="Male" ${user.gender=='Male'?'checked':''}>Male
                    <input type="radio" name="gender" value="Female" ${user.gender=='Female'?'checked':''}>Female
                </td>
            </tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Save"></td>
            </tr>
        </table>
    </form>
    <br>
    <a href="UserServlet">Back to List</a>
</body>
</html>

7. 部署项目

将编写好的项目打包成 WAR 文件，并将其部署到 Tomcat 服务器中，启动 Tomcat 服务器，在浏览器中访问 `http://localhost:8080/项目名/UserServlet` 即可访问该系统。

至此，一个简单的基于 Servlet+jsp+javabean 的增删改查系统就完成了。