package org.hibernate.jpa.test;

@Entity
public class Product {
	@Id
	@GeneratedValue
	private Integer id;
	
	@OneToMany(fetch = LAZY, cascade = ALL, orphanRemoval = true)
	private List<Widget> widgets;

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public void setWidgets(List<Widget> widgets) {
		this.widgets = widgets;
	}
}

package org.hibernate.jpa.test;

@Entity
public class Widget {
	private String name;
	private int id;

	public Widget() {

	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

}

//....
import com.google.common.collect.ImmutableList;
//....
public class EntityManagerTest extends BaseEntityManagerFunctionalTestCase {
//....
	@Test
	public void testSavingTwiceEntityWithImmutableCollection() {
		EntityManager em = getOrCreateEntityManager();
		em.getTransaction().begin();

		Widget widget1 = new Widget();
		widget1.setName("hammer");

		Widget widget2 = new Widget();
		widget2.setName("axel");

		Product p = new Product();
		p.setWidgets(ImmutableList.of(widget1, widget2));
		em.persist(p);

		p = em.getReference(Product.class,p.getId());
		em.merge(p);

		em.getTransaction().commit();
		em.clear();
		em.close();
	}
}