Working around HHH-9663: Orphan removal does not work for OneToOne relations

Craig Andrews

8 years ago

HHH-9663 means that orphan removal doesn’t work for OneToOne relationships. For example, given File and FileContent as below (taken from the bug report):

```
package pl.comit.orm.model;
```
```
 
```
```
import javax.persistence.Entity;
```
```
import javax.persistence.FetchType;
```
```
import javax.persistence.Id;
```
```
import javax.persistence.OneToOne;
```
```
 
```
```
@Entity
```
```
public class File {
```
```
 
```
```
	private int id;
```
```
 
```
```
	private FileContent content;
```
```
 
```
```
	@Id
```
```
	public int getId() {
```
```
		return id;
```
```
	}
```
```
 
```
```
	public void setId(int id) {
```
```
		this.id = id;
```
```
	}
```
```
 
```

	@OneToOne(fetch = FetchType.LAZY, orphanRemoval = true)

```
	public FileContent getContent() {
```
```
		return content;
```
```
	}
```
```
 
```

	public void setContent(FileContent content) {

```
		this.content = content;
```
```
	}
```
```
}
```

```
package pl.comit.orm.model;
```
```
 
```
```
import javax.persistence.Entity;
```
```
import javax.persistence.Id;
```
```
 
```
```
@Entity
```
```
public class FileContent {
```
```
 
```
```
	private int id;
```
```
 
```
```
	@Id
```
```
	public int getId() {
```
```
		return id;
```
```
	}
```
```
 
```
```
	public void setId(int id) {
```
```
		this.id = id;
```
```
	}
```
```
}
```

```
package pl.comit.orm.dao;
```
```
 
```
```
import javax.persistence.EntityManager;
```

import javax.persistence.PersistenceContext;

```
 
```

import org.springframework.stereotype.Repository;

import org.springframework.transaction.annotation.Transactional;

```
 
```
```
import pl.comit.orm.model.File;
```
```
import pl.comit.orm.model.FileContent;
```
```
 
```
```
@Repository
```
```
public class Dao {
```
```
 
```
```
	@PersistenceContext
```
```
	private EntityManager entityManager;
```
```
 
```
```
	@Transactional
```

	public void assureCreatedTaskAndNote(int fileId, int contentId) {

		FileContent content = entityManager.find(FileContent.class, contentId);

```
		if (content == null) {
```
```
			content = new FileContent();
```
```
			content.setId(contentId);
```
```
			entityManager.persist(content);
```
```
		}
```
```
 
```

		File file = entityManager.find(File.class, fileId);

```
		if (file == null) {
```
```
			file = new File();
```
```
			file.setId(fileId);
```
```
			entityManager.persist(file);
```
```
		}
```
```
		file.setContent(content);
```
```
	}
```
```
 
```
```
	@Transactional
```

	public void removeContent(int fileId) {

		File file = entityManager.find(File.class, fileId);

```
		file.setContent(null);
```
```
	}
```
```
 
```

	public FileContent find(int contentId) {

		return entityManager.find(FileContent.class, contentId);

```
	}
```
```
}
```

Running this as the main class will result in an exception:

```
package pl.comit.orm;
```
```
 
```

import org.springframework.context.support.ClassPathXmlApplicationContext;

```
 
```
```
import pl.comit.orm.dao.Dao;
```
```
import pl.comit.orm.model.FileContent;
```
```
 
```
```
public final class Application {
```
```
 
```

	private static final String CFG_FILE = "applicationContext.xml";

```
 
```

	public static void main(String[] args) {

		test(new ClassPathXmlApplicationContext(CFG_FILE).getBean(Dao.class));

```
	}
```
```
 
```
```
	public static void test(Dao dao) {
```
```
		dao.assureCreatedTaskAndNote(1, 2);
```
```
		dao.removeContent(1);
```
```
		FileContent content = dao.find(2);
```
```
		if (content != null) {
```

			System.err.println("Content found: " + content);

```
		}
```
```
	}
```
```
}
```

A workaround is to manually remove and detach the old referent, and then persist the new referent. Here’s an updated File.java:

```
package pl.comit.orm.model;
```
```
 
```

import org.springframework.stereotype.Component;

```
 
```
```
import javax.annotation.PostConstruct;
```
```
import javax.annotation.PreDestroy;
```
```
import javax.persistence.Entity;
```
```
import javax.persistence.FetchType;
```
```
import javax.persistence.Id;
```
```
import javax.persistence.OneToOne;
```

import javax.persistence.PersistenceContext;

```
 
```
```
@Entity
```
```
public class File {
```
```
 
```
```
	private int id;
```
```
 
```
```
	private FileContent content;
```
```
 
```
```
	@Id
```
```
	public int getId() {
```
```
		return id;
```
```
	}
```
```
 
```
```
	public void setId(int id) {
```
```
		this.id = id;
```
```
	}
```
```
 
```

	@OneToOne(fetch = FetchType.LAZY, orphanRemoval = true)

```
	public FileContent getContent() {
```
```
		return content;
```
```
	}
```
```
 
```

	public void setContent(FileContent content) {

```
		if(this.content != content){
```
```
			final oldContent = this.content;
```
```
			this.content = content;
```
```
			if(oldContent!=null){
```

				// Hibernate won't remove the oldContent for us, so do it manually; workaround HHH-9663

				WorkaroundHHH9663.entityManager.remove(oldContent);

				WorkaroundHHH9663.entityManager.detach(oldContent);

```
			}
```
```
		}
```
```
	}
```
```
 
```

	// WORKAROUND https://hibernate.atlassian.net/browse/HHH-9663 "Orphan removal does not work for OneToOne relations"

```
	@Component
```

	public static class WorkaroundHHH9663 {

```
		@PersistenceContext
```

		private EntityManager injectedEntityManager;

```
 
```

		private static EntityManager entityManager;

```
 
```
```
		@PostConstruct
```
```
		public void postConstruct(){
```

			entityManager = injectedEntityManager;

```
		}
```
```
 
```
```
		@PreDestroy
```
```
		public void preDestroy(){
```
```
			this.entityManager = null; // NOPMD
```
```
		}
```
```
	}
```
```
	// END WORKAROUND
```
```
}
```

Note that no Dao changes were made, so if, for example, Spring Data was used instead of such a Dao, you wouldn’t have to modify anything else. And you can just remove this workaround code easily when a version of Hibernate because available with HHH-9963 fixed.
Finally, yes, this approach does exhibit a bit of code smell (the use of the static variable in this way and the entity having a container managed component aren’t exactly best practices), but, it’s a workaround – hopefully just a temporary one.

Working around HHH-9663: Orphan removal does not work for OneToOne relations by Craig Andrews is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.