用javaweb实现用户管理的简易代码

下面是一个简单的用户管理系统的JavaWeb实现代码，包含用户的增删改查操作：

创建一个User类，用于存储用户信息：

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

    public User(int id, String name, int age, String email) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.email = email;
    }

    // getter and setter methods

}

创建一个UserDao类，用于对用户信息进行增删改查操作：

public class UserDao {

    private static List<User> userList = new ArrayList<>();

    // 添加用户
    public void addUser(User user) {
        userList.add(user);
    }

    // 删除用户
    public void deleteUser(int id) {
        for (User user : userList) {
            if (user.getId() == id) {
                userList.remove(user);
                break;
            }
        }
    }

    // 更新用户信息
    public void updateUser(User user) {
        for (User u : userList) {
            if (u.getId() == user.getId()) {
                u.setName(user.getName());
                u.setAge(user.getAge());
                u.setEmail(user.getEmail());
                break;
            }
        }
    }

    // 根据ID查询用户信息
    public User getUserById(int id) {
        for (User user : userList) {
            if (user.getId() == id) {
                return user;
            }
        }
        return null;
    }

    // 获取所有用户信息
    public List<User> getAllUsers() {
        return userList;
    }
}

创建一个Servlet类，用于处理用户请求：

@WebServlet("/user/*")
public class UserServlet extends HttpServlet {

    private UserDao userDao;

    // 初始化操作
    public void init() {
        userDao = new UserDao();
    }

    // 处理GET请求
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String pathInfo = request.getPathInfo();
        if (pathInfo == null) {
            // 获取所有用户信息
            List<User> userList = userDao.getAllUsers();
            request.setAttribute("userList", userList);
            request.getRequestDispatcher("/user-list.jsp").forward(request, response);
        } else {
            int id = Integer.parseInt(pathInfo.substring(1));
            User user = userDao.getUserById(id);
            request.setAttribute("user", user);
            request.getRequestDispatcher("/user-form.jsp").forward(request, response);
        }
    }

    // 处理POST请求
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String action = request.getParameter("action");
        if (action.equals("add")) {
            // 添加用户
            int id = Integer.parseInt(request.getParameter("id"));
            String name = request.getParameter("name");
            int age = Integer.parseInt(request.getParameter("age"));
            String email = request.getParameter("email");
            User user = new User(id, name, age, email);
            userDao.addUser(user);
            response.sendRedirect(request.getContextPath() + "/user");
        } else if (action.equals("update")) {
            // 更新用户信息
            int id = Integer.parseInt(request.getParameter("id"));
            String name = request.getParameter("name");
            int age = Integer.parseInt(request.getParameter("age"));
            String email = request.getParameter("email");
            User user = new User(id, name, age, email);
            userDao.updateUser(user);
            response.sendRedirect(request.getContextPath() + "/user");
        } else if (action.equals("delete")) {
            // 删除用户
            int id = Integer.parseInt(request.getParameter("id"));
            userDao.deleteUser(id);
            response.sendRedirect(request.getContextPath() + "/user");
        }
    }
}

创建两个JSP页面，一个用于显示用户列表，一个用于添加/更新用户信息：

user-list.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>User List</title>
</head>
<body>
    <h1>User List</h1>
    <table border="1">
        <thead>
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Age</th>
            <th>Email</th>
            <th>Action</th>
        </tr>
        </thead>
        <tbody>
        <c:forEach items="${userList}" var="user">
            <tr>
                <td>${user.id}</td>
                <td>${user.name}</td>
                <td>${user.age}</td>
                <td>${user.email}</td>
                <td>
                    <a href="${pageContext.request.contextPath}/user/${user.id}">Edit</a>
                    <form action="${pageContext.request.contextPath}/user" method="post">
                        <input type="hidden" name="id" value="${user.id}">
                        <input type="hidden" name="action" value="delete">
                        <input type="submit" value="Delete">
                    </form>
                </td>
            </tr>
        </c:forEach>
        </tbody>
    </table>

    <hr>

    <h2>Add User</h2>
    <form action="${pageContext.request.contextPath}/user" method="post">
        <input type="hidden" name="action" value="add">
        <label>ID:</label>
        <input type="text" name="id"><br>
        <label>Name:</label>
        <input type="text" name="name"><br>
        <label>Age:</label>
        <input type="text" name="age"><br>
        <label>Email:</label>
        <input type="text" name="email"><br>
        <input type="submit" value="Add">
    </form>
</body>
</html>

user-form.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>User Form</title>
</head>
<body>
    <h1>User Form</h1>
    <% if (user == null) { %>
        <h2>Add User</h2>
        <form action="${pageContext.request.contextPath}/user" method="post">
            <input type="hidden" name="action" value="add">
            <label>ID:</label>
            <input type="text" name="id"><br>
            <label>Name:</label>
            <input type="text" name="name"><br>
            <label>Age:</label>
            <input type="text" name="age"><br>
            <label>Email:</label>
            <input type="text" name="email"><br>
            <input type="submit" value="Add">
        </form>
    <% } else { %>
        <h2>Edit User</h2>
        <form action="${pageContext.request.contextPath}/user" method="post">
            <input type="hidden" name="action" value="update">
            <input type="hidden" name="id" value="${user.id}">
            <label>ID:</label>
            <input type="text" name="id" value="${user.id}" disabled><br>
            <label>Name:</label>
            <input type="text" name="name" value="${user.name}"><br>
            <label>Age:</label>
            <input type="text" name="age" value="${user.age}"><br>
            <label>Email:</label>
            <input type="text" name="email" value="${user.email}"><br>
            <input type="submit" value="Update">
        </form>
    <% } %>
</body>
</html>

配置web.xml文件，将UserServlet映射到/user路径下：

<servlet>
    <servlet-name>UserServlet</servlet-name>
    <servlet-class>com.example.UserServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>UserServlet</servlet-name>
    <url-pattern>/user/*</url-pattern>
</servlet-mapping>

现在，我们就实现了一个简单的用户管理系统，可以对用户信息进行增删改查操作