public interface StudentService {

  public Student getStudent(String login);

  public void registerStudent(Student student);

  public java.util.Set getCompletedCourses(Student student);

  public String getCurrentUserId();

}

public interface CourseService {

  public Course getCourse(int id);

  public Course getCourse(Integer id);

  public void saveCourse(Course course);

  public java.util.Set getAllCourses();

  public void enrollStudentInCourse(Course course, Student student) throws CourseException;

  public void sendCourseEnrollmentReport();

}

public class StudentServiceImpl implements StudentService {

  Logger LOGGER = Logger.getLogger(StudentServiceImpl.class);

  private StudentDao studentDao;

  // 생성자에 의한 주입

  public StudentServiceImpl(StudentDao dao) {

    studentDao = dao;

  }

  // setter에 의한 주입

  // 참고: 소스에는 없다. 다만, 원리를 설명하기 위함.

  public setStudentDao(StudentDao dao) {

    studentDao = dao;

  }

  public Student getStudent(String login) {

    return studentDao.findById(login);

  }

  public void registerStudent(Student student) {

    HashSet authorities = new HashSet();

    authorities.add(new Authority("ROLE_STUDENT"));

    authorities.add(new Authority("ROLE_USER"));

    student.setAuthorities(authorities);

    studentDao.create(student);

  }

  public java.util.Set getCompletedCourses(Student student) {

    return studentDao.getCompletedCourses(student);

  }

  /*

   * TODO - This could be used more generically for Instructors as well.

   * But since it's only used for Students right now and because it would

   * be silly to create a UserService for this simple method, we'll just

   * put it here for now.

   */

  public String getCurrentUserId() {

    return ((SecureContext)ContextHolder.getContext()).getAuthentication().getPrincipal().toString();

  }

}

public class CourseServiceImpl implements CourseService {

  private static Logger LOGGER = Logger.getLogger(CourseServiceImpl.class);

  // 생성자 주입을 통한 CourseDao 설정

  public CourseServiceImpl(CourseDao dao) {

    this.courseDao = dao;

  }

  public Course getCourse(int id) {

    return getCourse(new Integer(id));

  }

  public Course getCourse(Integer id) {

    return courseDao.findById(id);

  }

  public void saveCourse(Course course) {

    courseDao.save(course);

  }

  public void enrollStudentInCourse(Course course,

      Student student) throws CourseException {

    // TODO:    enforcePrerequisites(course, student);

    // TODO:    Check for schedule conflicts

    course.getStudents().add(student);

    courseDao.save(course);

  }

  public Set getAllCourses() {

    return courseDao.findAll();

  }

  public void sendCourseEnrollmentReport() {

    Set courseList = courseDao.findAll();

    SimpleMailMessage message =

        new SimpleMailMessage(this.mailMessage);

    StringBuffer messageText = new StringBuffer();

    messageText.append("Current enrollment data is as follows:\n\n");

    for(Iterator iter = courseList.iterator(); iter.hasNext(); ) {

      Course course = (Course) iter.next();

      messageText.append(course.getId() + "    ");

      messageText.append(course.getName() + "    ");

      int enrollment = courseDao.getEnrollment(course);

      messageText.append(enrollment);

    }

    message.setText(messageText.toString());

    try {

      mailSender.send(message);

    } catch (MailException e) {

      LOGGER.error(e.getMessage());

    }

  }

  private void enforcePrerequisites(Course course,

      Student student) throws CourseException {

    Set completed = studentService.getCompletedCourses(student);

    // Check for prerequesites

    Set prereqs = course.getPrerequisites();

    for(Iterator iter = prereqs.iterator(); iter.hasNext(); ) {

      if(!completed.contains(iter.next())) {

        throw new CourseException("Prerequisites are not met.");

      }

    }

    // Check for scheduling clash

    for(Iterator iter = completed.iterator(); iter.hasNext(); ) {

      Course completedCourse = (Course) iter.next();

    }

  }

  // COLLABORATORS

  private CourseDao courseDao;

  public void setCourseDao(CourseDao courseDao) {

    this.courseDao = courseDao;

  }

  private StudentService studentService;

  public void setStudentService(StudentService service) {

    this.studentService = service;

  }

  private MailSender mailSender;

  public void setMailSender(MailSender mailSender) {

    this.mailSender = mailSender;

  }

  private SimpleMailMessage mailMessage;

  public void setMailMessage(SimpleMailMessage mailMessage) {

    this.mailMessage = mailMessage;

  }

}