帮我写一个基于java web的学生信息管理系统

好的，下面是一个简单的学生信息管理系统的Java Web实现。这个系统包含了学生信息的增删改查功能。

首先，我们需要定义学生实体类，包含学生的基本信息：

public class Student {
    private int id; // 学号
    private String name; // 姓名
    private int age; // 年龄
    private String gender; // 性别

    // 构造函数
    public Student(int id, String name, int age, String gender) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    // getter和setter方法
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    public String getGender() {
        return gender;
    }

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

接下来，我们需要创建一个学生信息管理类，包含增删改查等方法：

public class StudentManager {
    private static Map<Integer, Student> students = new HashMap<>(); // 用Map存储学生信息

    // 添加学生信息
    public static void addStudent(Student student) {
        students.put(student.getId(), student);
    }

    // 删除学生信息
    public static void deleteStudent(int id) {
        students.remove(id);
    }

    // 修改学生信息
    public static void updateStudent(Student student) {
        students.put(student.getId(), student);
    }

    // 查询学生信息
    public static List<Student> queryStudent(String name) {
        List<Student> list = new ArrayList<>();
        for (Student student : students.values()) {
            if (student.getName().equals(name)) {
                list.add(student);
            }
        }
        return list;
    }

    // 获取所有学生信息
    public static List<Student> getAllStudents() {
        return new ArrayList<>(students.values());
    }
}

接下来，我们需要创建一个Servlet来处理学生信息的增删改查请求：

public class StudentServlet extends HttpServlet {
    // 处理GET请求
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");

        if (action == null) {
            action = "list";
        }

        // 查询学生信息
        if (action.equals("query")) {
            String name = request.getParameter("name");
            List<Student> list = StudentManager.queryStudent(name);
            request.setAttribute("students", list);
            request.getRequestDispatcher("/query.jsp").forward(request, response);
        }
        // 显示所有学生信息
        else if (action.equals("list")) {
            List<Student> list = StudentManager.getAllStudents();
            request.setAttribute("students", list);
            request.getRequestDispatcher("/list.jsp").forward(request, response);
        }
        // 显示添加学生信息的页面
        else if (action.equals("add")) {
            request.getRequestDispatcher("/add.jsp").forward(request, response);
        }
        // 处理添加学生信息的请求
        else if (action.equals("doAdd")) {
            int id = Integer.parseInt(request.getParameter("id"));
            String name = request.getParameter("name");
            int age = Integer.parseInt(request.getParameter("age"));
            String gender = request.getParameter("gender");

            Student student = new Student(id, name, age, gender);
            StudentManager.addStudent(student);

            response.sendRedirect("student?action=list");
        }
        // 显示修改学生信息的页面
        else if (action.equals("edit")) {
            int id = Integer.parseInt(request.getParameter("id"));
            Student student = StudentManager.getAllStudents().stream()
                    .filter(s -> s.getId() == id)
                    .findFirst()
                    .orElse(null);
            request.setAttribute("student", student);
            request.getRequestDispatcher("/edit.jsp").forward(request, response);
        }
        // 处理修改学生信息的请求
        else if (action.equals("doEdit")) {
            int id = Integer.parseInt(request.getParameter("id"));
            String name = request.getParameter("name");
            int age = Integer.parseInt(request.getParameter("age"));
            String gender = request.getParameter("gender");

            Student student = new Student(id, name, age, gender);
            StudentManager.updateStudent(student);

            response.sendRedirect("student?action=list");
        }
        // 处理删除学生信息的请求
        else if (action.equals("delete")) {
            int id = Integer.parseInt(request.getParameter("id"));
            StudentManager.deleteStudent(id);

            response.sendRedirect("student?action=list");
        }
    }

    // 处理POST请求
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

最后，我们需要创建一些JSP页面来显示学生信息、添加学生信息、修改学生信息等：

list.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>学生信息管理系统</title>
</head>
<body>
    <h1>学生信息列表</h1>
    <p><a href="student?action=add">添加学生信息</a></p>
    <table border="1">
        <tr>
            <th>学号</th>
            <th>姓名</th>
            <th>年龄</th>
            <th>性别</th>
            <th>操作</th>
        </tr>
        <c:forEach items="${students}" var="student">
            <tr>
                <td>${student.id}</td>
                <td>${student.name}</td>
                <td>${student.age}</td>
                <td>${student.gender}</td>
                <td>
                    <a href="student?action=edit&id=${student.id}">修改</a>
                    <a href="student?action=delete&id=${student.id}">删除</a>
                </td>
            </tr>
        </c:forEach>
    </table>
</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>学生信息管理系统</title>
</head>
<body>
    <h1>添加学生信息</h1>
    <form action="student" method="post">
        <input type="hidden" name="action" value="doAdd" />
        <p>学号：<input type="text" name="id" /></p>
        <p>姓名：<input type="text" name="name" /></p>
        <p>年龄：<input type="text" name="age" /></p>
        <p>性别：<input type="text" name="gender" /></p>
        <p><input type="submit" value="添加" /></p>
    </form>
</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>学生信息管理系统</title>
</head>
<body>
    <h1>修改学生信息</h1>
    <form action="student" method="post">
        <input type="hidden" name="action" value="doEdit" />
        <input type="hidden" name="id" value="${student.id}" />
        <p>学号：<input type="text" name="id" value="${student.id}" /></p>
        <p>姓名：<input type="text" name="name" value="${student.name}" /></p>
        <p>年龄：<input type="text" name="age" value="${student.age}" /></p>
        <p>性别：<input type="text" name="gender" value="${student.gender}" /></p>
        <p><input type="submit" value="保存" /></p>
    </form>
</body>
</html>

query.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>学生信息管理系统</title>
</head>
<body>
    <h1>查询学生信息</h1>
    <form action="student" method="get">
        <input type="hidden" name="action" value="query" />
        <p>姓名：<input type="text" name="name" /></p>
        <p><input type="submit" value="查询" /></p>
    </form>
    <table border="1">
        <tr>
            <th>学号</th>
            <th>姓名</th>
            <th>年龄</th>
            <th>性别</th>
        </tr>
        <c:forEach items="${students}" var="student">
            <tr>
                <td>${student.id}</td>
                <td>${student.name}</td>
                <td>${student.age}</td>
                <td>${student.gender}</td>
            </tr>
        </c:forEach>
    </table>
</body>
</html>

以上就是一个简单的学生信息管理系统的Java Web实现，你可以根据自己的需求对其进行修改和完善。