用javaweb写一下学生信息管理系统增删改查servlet类

以下是一个简单的学生信息管理系统的增删改查的Servlet类示例：

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/student")
public class StudentServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
    private List<Student> students;
    
    public StudentServlet() {
        super();
        students = new ArrayList<>();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        
        if (action == null) {
            action = "list";
        }
        
        switch (action) {
            case "list":
                listStudents(request, response);
                break;
            case "showAddForm":
                showAddForm(request, response);
                break;
            case "add":
                addStudent(request, response);
                break;
            case "showEditForm":
                showEditForm(request, response);
                break;
            case "edit":
                editStudent(request, response);
                break;
            case "delete":
                deleteStudent(request, response);
                break;
            default:
                listStudents(request, response);
                break;
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
    
    private void listStudents(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setAttribute("students", students);
        request.getRequestDispatcher("list.jsp").forward(request, response);
    }
    
    private void showAddForm(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.getRequestDispatcher("add.jsp").forward(request, response);
    }
    
    private void addStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String grade = request.getParameter("grade");
        
        Student student = new Student(name, Integer.parseInt(age), grade);
        students.add(student);
        
        response.sendRedirect("student");
    }
    
    private void showEditForm(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int studentId = Integer.parseInt(request.getParameter("id"));
        Student student = students.get(studentId);
        
        request.setAttribute("student", student);
        request.getRequestDispatcher("edit.jsp").forward(request, response);
    }
    
    private void editStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int studentId = Integer.parseInt(request.getParameter("id"));
        Student student = students.get(studentId);
        
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String grade = request.getParameter("grade");
        
        student.setName(name);
        student.setAge(Integer.parseInt(age));
        student.setGrade(grade);
        
        response.sendRedirect("student");
    }
    
    private void deleteStudent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int studentId = Integer.parseInt(request.getParameter("id"));
        students.remove(studentId);
        
        response.sendRedirect("student");
    }
}

这个Servlet类中，通过不同的action参数来执行不同的操作，包括显示学生列表、显示添加学生的表单、添加学生、显示编辑学生的表单、编辑学生、删除学生等。具体的操作逻辑在各个方法中实现。