Java中使用DAO模式的多对多关系

public class Student {
    private int id;
    private String name;
    // other attributes and getters/setters
}

public class Course {
    private int id;
    private String name;
    // other attributes and getters/setters
}

public interface StudentDAO {
    void addCourse(Student student, Course course);
    void removeCourse(Student student, Course course);
    List<Course> getCourses(Student student);
}

public class StudentDAOImpl implements StudentDAO {
    // implementation of addCourse, removeCourse, getCourses methods
}

public interface CourseDAO {
    void addStudent(Course course, Student student);
    void removeStudent(Course course, Student student);
    List<Student> getStudents(Course course);
}

public class CourseDAOImpl implements CourseDAO {
    // implementation of addStudent, removeStudent, getStudents methods
}

public class StudentService {
    private StudentDAO studentDAO;
    private CourseDAO courseDAO;
    
    public void addCourseToStudent(Student student, Course course) {
        studentDAO.addCourse(student, course);
        courseDAO.addStudent(course, student);
    }
    
    public void removeCourseFromStudent(Student student, Course course) {
        studentDAO.removeCourse(student, course);
        courseDAO.removeStudent(course, student);
    }
    
    public List<Course> getCoursesOfStudent(Student student) {
        return studentDAO.getCourses(student);
    }
}

public class CourseService {
    private CourseDAO courseDAO;
    private StudentDAO studentDAO;
    
    public void addStudentToCourse(Course course, Student student) {
        courseDAO.addStudent(course, student);
        studentDAO.addCourse(student, course);
    }
    
    public void removeStudentFromCourse(Course course, Student student) {
        courseDAO.removeStudent(course, student);
        studentDAO.removeCourse(student, course);
    }
    
    public List<Student> getStudentsOfCourse(Course course) {
        return courseDAO.getStudents(course);
    }
}