Understanding the org.hibernate.PersistentObjectException Error in JPA and Hibernate

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If you're diving into JPA and Hibernate for a project and have encountered the error message

Understanding the Error

When you attempt to persist an entity that already has an assigned identifier (ID), Hibernate assumes it is an existing entity and tries to manage its state. If it can’t find this entity in its persistence context or the database, it throws the PersistentObjectException. In simpler terms, this means that Hibernate is being told to save something that it thinks already exists, but it can't find it anywhere.

Your Context

In your case, you were working on a project to store continents, countries, and cities in a PostgreSQL database, and when you tried to persist a new continent entity, the error popped up. Here’s the essence of the problem based on your provided code snippet:

[[See Video to Reveal this Text or Code Snippet]]

When you specify the ID beforehand, Hibernate is left unsure whether to treat this as a new entity or an existing one.

The Solution: Persisting Without ID

To resolve this issue, you should remove the manual setting of the ID before persisting the entity. Let Hibernate handle ID generation for you. This way, Hibernate will regard the entity as new:

Remove the Manual ID Setting

Don't set the ID explicitly. Let it be auto-generated by the database.

Modify your code as follows:

[[See Video to Reveal this Text or Code Snippet]]

Ensure Correct Database Design

You mentioned that your database design was not optimal. Make your primary keys (id fields) auto-incrementing (e.g., using SERIAL in PostgreSQL).

A correctly designed schema will ensure Hibernate can automatically assign IDs when new entities are created. Here's how you might define the continents table:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

If you have any further questions or need assistance, feel free to reach out!