manytomanytestsessionbean.java

EJB3.0实现学生、社团实体及它们的M:M关系

package ManyToManySessionBean;

import javax.ejb.Stateless;
import ManyToManyEntityBean.*;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
public class ManyToManyTestSessionBean implements
		ManyToManyTestSessionBeanRemote {
	@PersistenceContext
	protected EntityManager em;

	public void insertConsortium(String name, String[] studentnames) {
		Consortium consortium = new Consortium(name);
		if (studentnames != null) {
			for (int i = 0; i < studentnames.length; i++) {
				consortium.addStudent(new Student(studentnames[i]));
			}
		}
		em.persist(consortium);
	}

	public Consortium getConsortiumByID(Integer consortiumid) {
		Consortium consortium = em.find(Consortium.class, consortiumid);
		if (consortium != null)
			consortium.getStudents().size();
		return consortium;
	}

	public Student getStudentByID(Integer studentid) {
		Student student = em.find(Student.class, studentid);
		if (student != null)
			student.getConsortiums().size();
		return student;
	}

}