基于java web的学生管理系统，实现增删查改

要实现基于Java Web的学生管理系统，可以按照以下步骤：

1. 创建数据库表格
首先需要创建数据库表格，包括学生信息的各个字段，例如学生ID、姓名、性别、年龄、班级等。

2. 创建JavaBean类
创建一个JavaBean类，用来存储学生信息，包括各个字段的setter和getter方法。

3. 创建DAO层
创建一个DAO层，用来对数据库进行增删查改操作，包括添加学生、删除学生、查询学生、更新学生信息等。

4. 创建Servlet层
创建一个Servlet层，用来接收前端请求，将请求参数传递给DAO层进行数据库操作，并将操作结果返回给前端。

5. 创建JSP页面
创建一个JSP页面，用来展示学生信息、添加学生、修改学生信息等。

6. 部署应用
将应用部署到服务器上，例如Tomcat服务器，让用户可以通过浏览器访问学生管理系统。

具体实现方法可以参考以下示例代码：

1. 创建数据库表格

CREATE TABLE student (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(20),
    gender VARCHAR(10),
    age INT,
    class VARCHAR(20)
);

2. 创建JavaBean类

public class Student {
    private int id;
    private String name;
    private String gender;
    private int age;
    private String clazz;
    
    // setter and getter methods
}

3. 创建DAO层

public class StudentDAO {
    private static final String URL = "jdbc:mysql://localhost:3306/studentdb";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "root";
    
    public void addStudent(Student student) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
             PreparedStatement ps = conn.prepareStatement("INSERT INTO student(name, gender, age, class) VALUES (?, ?, ?, ?)")) {
            ps.setString(1, student.getName());
            ps.setString(2, student.getGender());
            ps.setInt(3, student.getAge());
            ps.setString(4, student.getClazz());
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public void deleteStudent(int id) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
             PreparedStatement ps = conn.prepareStatement("DELETE FROM student WHERE id = ?")) {
            ps.setInt(1, id);
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public Student getStudentById(int id) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
             PreparedStatement ps = conn.prepareStatement("SELECT * FROM student WHERE id = ?")) {
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                Student student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setGender(rs.getString("gender"));
                student.setAge(rs.getInt("age"));
                student.setClazz(rs.getString("class"));
                return student;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    
    public List<Student> getAllStudents() {
        List<Student> students = new ArrayList<>();
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
             PreparedStatement ps = conn.prepareStatement("SELECT * FROM student")) {
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
                Student student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setGender(rs.getString("gender"));
                student.setAge(rs.getInt("age"));
                student.setClazz(rs.getString("class"));
                students.add(student);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return students;
    }
    
    public void updateStudent(Student student) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
             PreparedStatement ps = conn.prepareStatement("UPDATE student SET name = ?, gender = ?, age = ?, class = ? WHERE id = ?")) {
            ps.setString(1, student.getName());
            ps.setString(2, student.getGender());
            ps.setInt(3, student.getAge());
            ps.setString(4, student.getClazz());
            ps.setInt(5, student.getId());
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

4. 创建Servlet层

public class StudentServlet extends HttpServlet {
    private StudentDAO studentDAO = new StudentDAO();
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if ("add".equals(action)) {
            addStudent(request, response);
        } else if ("delete".equals(action)) {
            deleteStudent(request, response);
        } else if ("update".equals(action)) {
            updateStudent(request, response);
        }
    }
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if ("list".equals(action)) {
            listStudents(request, response);
        } else if ("edit".equals(action)) {
            editStudent(request, response);
        }
    }
    
    private void addStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        String gender = request.getParameter("gender");
        int age = Integer.parseInt(request.getParameter("age"));
        String clazz = request.getParameter("class");
        Student student = new Student();
        student.setName(name);
        student.setGender(gender);
        student.setAge(age);
        student.setClazz(clazz);
        studentDAO.addStudent(student);
        response.sendRedirect("student?action=list");
    }
    
    private void deleteStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        studentDAO.deleteStudent(id);
        response.sendRedirect("student?action=list");
    }
    
    private void updateStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        String gender = request.getParameter("gender");
        int age = Integer.parseInt(request.getParameter("age"));
        String clazz = request.getParameter("class");
        Student student = new Student();
        student.setId(id);
        student.setName(name);
        student.setGender(gender);
        student.setAge(age);
        student.setClazz(clazz);
        studentDAO.updateStudent(student);
        response.sendRedirect("student?action=list");
    }
    
    private void listStudents(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Student> students = studentDAO.getAllStudents();
        request.setAttribute("students", students);
        request.getRequestDispatcher("list.jsp").forward(request, response);
    }
    
    private void editStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        Student student = studentDAO.getStudentById(id);
        request.setAttribute("student", student);
        request.getRequestDispatcher("edit.jsp").forward(request, response);
    }
}

5. 创建JSP页面

<!-- list.jsp -->
<%@ 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>学生管理系统</title>
</head>
<body>
    <h1>学生管理系统</h1>
    <table border="1">
        <thead>
            <tr>
                <th>ID</th>
                <th>姓名</th>
                <th>性别</th>
                <th>年龄</th>
                <th>班级</th>
                <th>操作</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach items="${students}" var="student">
                <tr>
                    <td>${student.id}</td>
                    <td>${student.name}</td>
                    <td>${student.gender}</td>
                    <td>${student.age}</td>
                    <td>${student.clazz}</td>
                    <td>
                        <a href="student?action=edit&id=${student.id}">编辑</a>
                        <a href="student?action=delete&id=${student.id}">删除</a>
                    </td>
                </tr>
            </c:forEach>
        </tbody>
    </table>
    <br>
    <a href="add.jsp">添加学生</a>
</body>
</html>

<!-- edit.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>学生管理系统</title>
</head>
<body>
    <h1>学生管理系统</h1>
    <form action="student" method="post">
        <input type="hidden" name="action" value="update">
        <input type="hidden" name="id" value="${student.id}">
        姓名：<input type="text" name="name" value="${student.name}"><br>
        性别：<input type="radio" name="gender" value="男" ${student.gender == '男' ? 'checked' : ''}>男
            <input type="radio" name="gender" value="女" ${student.gender == '女' ? 'checked' : ''}>女<br>
        年龄：<input type="text" name="age" value="${student.age}"><br>
        班级：<input type="text" name="class" value="${student.clazz}"><br>
        <input type="submit" value="保存">
    </form>
    <br>
    <a href="student?action=list">返回列表</a>
</body>
</html>

<!-- add.jsp -->
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>学生管理系统</title>
</head>
<body>
    <h1>学生管理系统</h1>
    <form action="student" method="post">
        <input type="hidden" name="action" value="add">
        姓名：<input type="text" name="name"><br>
        性别：<input type="radio" name="gender" value="男" checked>男
            <input type="radio" name="gender" value="女">女<br>
        年龄：<input type="text" name="age"><br>
        班级：<input type="text" name="class"><br>
        <input type="submit" value="添加">
    </form>
    <br>
    <a href="student?action=list">返回列表</a>
</body>
</html>

6. 部署应用
将上述代码打包成war包，部署到Tomcat服务器上即可。用户可以通过访问http://localhost:8080/项目名/student?action=list来访问学生管理系统。