Java Web 学生信息管理系统：使用 Servlet 实现增删改查

首先，我们需要创建一个名为'Student'的Java类，该类包含姓名、性别、学号和班级等属性，并提供相应的getter和setter方法。

public class Student {
    private String name;
    private String gender;
    private String studentId;
    private String className;

    public Student(String name, String gender, String studentId, String className) {
        this.name = name;
        this.gender = gender;
        this.studentId = studentId;
        this.className = className;
    }

    // Getter and Setter methods
    // ...

    @Override
    public String toString() {
        return 'Student{' +
                "name='" + name + "'"
                + ", gender='" + gender + "'"
                + ", studentId='" + studentId + "'"
                + ", className='" + className + "'"
                + '}';
    }
}

接下来，我们需要创建一个名为'StudentServlet'的Servlet类。在该类中，我们可以使用一个静态的HashMap来存储学生信息，学号作为键，学生对象作为值。

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class StudentServlet extends HttpServlet {
    private static Map<String, Student> studentMap = new HashMap<>();

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String studentId = request.getParameter("studentId");
        Student student = studentMap.get(studentId);

        if (student != null) {
            response.getWriter().write(student.toString());
        } else {
            response.getWriter().write("Student not found");
        }
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String name = request.getParameter("name");
        String gender = request.getParameter("gender");
        String studentId = request.getParameter("studentId");
        String className = request.getParameter("className");

        Student student = new Student(name, gender, studentId, className);
        studentMap.put(studentId, student);

        response.getWriter().write("Student added successfully");
    }

    @Override
    protected void doPut(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String studentId = request.getParameter("studentId");
        String name = request.getParameter("name");
        String gender = request.getParameter("gender");
        String className = request.getParameter("className");

        Student student = studentMap.get(studentId);
        if (student != null) {
            student.setName(name);
            student.setGender(gender);
            student.setClassName(className);
            response.getWriter().write("Student updated successfully");
        } else {
            response.getWriter().write("Student not found");
        }
    }
}

在上述代码中，doGet方法用于根据学号查询学生信息，doPost方法用于添加学生信息，doPut方法用于更新学生信息。最后，我们需要在web.xml文件中配置Servlet映射。

<servlet>
    <servlet-name>StudentServlet</servlet-name>
    <servlet-class>com.example.StudentServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>StudentServlet</servlet-name>
    <url-pattern>/student/*</url-pattern>
</servlet-mapping>

这样，我们就可以通过发送HTTP请求来访问和操作学生信息了。例如，使用GET请求访问'/student?studentId=123'可以查询学号为123的学生信息；使用POST请求访问'/student'可以添加学生信息；使用PUT请求访问'/student?studentId=123'可以更新学号为123的学生信息。