student-management/src/main/java/com/student/service/EnrollmentService.java

package com.student.service;

import com.student.bean.Course;
import com.student.bean.Enrollment;
import com.student.dao.CourseDao;
import com.student.dao.EnrollmentDao;
import com.student.dao.impl.CourseDaoImpl;
import com.student.dao.impl.EnrollmentDaoImpl;

import java.util.List;

public class EnrollmentService {

    private final EnrollmentDao enrollmentDao;
    private final CourseDao courseDao;

    public EnrollmentService() {
        this(new EnrollmentDaoImpl(), new CourseDaoImpl());
    }

    EnrollmentService(EnrollmentDao enrollmentDao, CourseDao courseDao) {
        this.enrollmentDao = enrollmentDao;
        this.courseDao = courseDao;
    }

    public boolean enroll(int studentId, int courseId) {
        if (enrollmentDao.exists(studentId, courseId)) {
            throw new RuntimeException("已选过该课程");
        }
        Course course = courseDao.findById(courseId);
        if (course == null) {
            throw new RuntimeException("课程不存在");
        }
        int count = enrollmentDao.countByCourse(courseId);
        if (course.getMaxStudents() != null && count >= course.getMaxStudents()) {
            throw new RuntimeException("课程已满");
        }
        return enrollmentDao.enroll(studentId, courseId);
    }

    public boolean cancel(int studentId, int courseId) {
        return enrollmentDao.cancel(studentId, courseId);
    }

    public List<Enrollment> findByStudent(int studentId) {
        return enrollmentDao.findByStudent(studentId);
    }

    public List<Enrollment> findByCourse(int courseId) {
        return enrollmentDao.findByCourse(courseId);
    }

    public int countByCourse(int courseId) {
        return enrollmentDao.countByCourse(courseId);
    }
}