Org.Hibernate.PersistentObjectException: Detached Entity Passed To Persist (Resolved)

The "detached entity passed to persist" error occurs when you try to persist a detached entity (i.e. an entity that is not attached to the current Hibernate session) to the database.

To resolve this error, you can follow these steps:

1. Reattach the detached entity to the current Hibernate session using the Session.merge() method.
2. Retrieve the entity from the database using the Session.get() method, make your changes to the retrieved entity, and then call the Session.flush() method to synchronize the changes with the database.
3. Create a new instance of the entity and persist it to the database using the Session.persist() method.

In general, the best approach is to use the Session.merge() method to reattach the detached entity to the current Hibernate session. This is because the Session.merge() method returns a new instance of the entity that is attached to the current Hibernate session, and any changes made to this instance will be synchronized with the database.

It is important to ensure that the detached entity is properly managed in your application, as it can lead to various errors and unexpected behavior. One common cause of detached entities is serialization/deserialization of entities, which can cause the entity to become detached from the current Hibernate session. To avoid this, it is recommended to avoid serializing entities, or to use lazy loading and fetching strategies when serializing entities.

It is also important to use transactions and the Hibernate session properly. The Hibernate session should be opened at the beginning of a transaction, used to persist or retrieve entities, and closed at the end of the transaction. This ensures that the entities are properly managed and attached/detached from the Hibernate session as needed.

In summary, to resolve the "detached entity passed to persist" error, you should reattach the entity to the current Hibernate session using Session.merge() or retrieve the entity from the database, properly manage the Hibernate session and transactions, and avoid serializing entities or use appropriate fetching strategies when serializing.

org.hibernate.PersistentObjectException: detached entity passed to persist

I had successfully written my first master child example with hibernate. After few days I took it again and upgraded some libraries. No sure what did I do but I could never make it run again. Would

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Frequently Asked Questions About The Error

What is a detached entity in Hibernate?

A detached entity is an entity that is not attached to the current Hibernate session. It can be created outside of the current Hibernate session, for example, through serialization/deserialization.

What causes the "detached entity passed to persist" error in Hibernate?

The error occurs when you try to persist a detached entity to the database using the Session.persist() method.

How do I fix the "detached entity passed to persist" error in Hibernate?

You can fix the error by reattaching the detached entity to the current Hibernate session using the Session.merge() method, or by retrieving the entity from the database, making changes to it, and then synchronizing the changes with the database using Session.flush().

Can I avoid the "detached entity passed to persist" error by serializing the entity before persist?

No, serializing the entity before persist will not avoid the error. In fact, it can cause the entity to become detached from the Hibernate session, leading to the error. It is recommended to avoid serializing entities, or to use lazy loading and fetching strategies when serializing entities.

Why is it important to properly manage the Hibernate session and transactions?

Properly managing the Hibernate session and transactions is important because it ensures that entities are attached or detached from the Hibernate session as needed, and changes made to entities are properly synchronized with the database. Improperly managed Hibernate sessions and transactions can lead to various errors and unexpected behavior.

What is the difference between the Session.persist() and Session.merge() methods in Hibernate?

The Session.persist() method is used to persist a new entity to the database, or to reattach a detached entity to the current Hibernate session. The Session.merge() method, on the other hand, is used to merge the state of a detached entity with the current Hibernate session. The Session.merge() method returns a new instance of the entity that is attached to the current Hibernate session, and any changes made to this instance will be synchronized with the database.

What are some best practices for avoiding the "detached entity passed to persist" error in Hibernate?

Some best practices for avoiding the error include: properly managing the Hibernate session and transactions, avoiding serializing entities or using appropriate fetching strategies when serializing, using the Session.merge() method to reattach detached entities to the Hibernate session, and regularly synchronizing changes with the database using Session.flush().

How can I determine if an entity is detached from the Hibernate session?

You can determine if an entity is detached from the Hibernate session by checking if it is associated with the current Hibernate session using the Session.contains() method. If the method returns false, then the entity is detached from the Hibernate session.