Web apps rely on databases to store, maintain and retrieve user data. Hibernate is a common object-relational mapping for Java application development that uses Database management systems (DBMS). It allows data to be represented and manipulated as objects.
But sometimes due to incorrect usage or incompatibility between the Hibernate and its DBMS counterpart, you may encounter various errors. One of them is the "org.hibernate.persistentobjectexception: detached entity passed to persist" error.
What Causes the Detached Entity Error
The “org.hibernate.persistentobjectexception: detached entity passed to persist” error is a common Hibernate exception. It is caused when a detached entity is passed to Hibernate’s persist() method. A detached entity is an object that has been detached from session and is no longer associated with it. When you pass a detached entity to persist(), the session can no longer track the changes you made to the entity.
How to Fix the Detached Entity Error
Fixing the “org.hibernate.persistentobjectexception: detached entity passed to persist” error is simple. The solution is to reattach the detached entity to the session by calling the update() method on the session object. This will associate the detached entity with the current session and allow you to persist the changes.
The following code snippet demonstrates how to reattach a detached entity using the update() method in Hibernate:
Session session = sessionFactory.openSession();
Person p = (Person)session.get(Person.class, id);
//detached entity
session.close();
Session session = sessionFactory.openSession();
session.update(p); //reattach the detached entity
session.saveOrUpdate(p);
session.close();
FAQs
Q1. What is Hibernate?
A1. Hibernate is an open-source object-relational mapping library for Java application development. It provides tools for mapping object-oriented domain models to relational databases for storing and retrieving user data.
Q2. What is the “org.hibernate.persistentobjectexception: detached entity passed to persist” error?
A2. The “org.hibernate.persistentobjectexception: detached entity passed to persist” error is a common Hibernate exception, caused when a detached entity is passed to the persist() method.
Q3. What causes the detached entity error?
A3. The detached entity error is caused when a detached entity is passed to Hibernate’s persist() method. A detached entity is an object that has been detached from session and is no longer associated with it.
Q4. How do you fix the detached entity error?
A4. The solution is to reattach the detached entity to the session by calling the update() method on the session object. This will associate the detached entity with the current session and allow you to persist the changes.
Q5. What is the code snippet to reattach a detached entity?
A5. The following code snippet demonstrates how to reattach a detached entity using the update() method in Hibernate:
Session session = sessionFactory.openSession();
Person p = (Person)session.get(Person.class, id);
//detached entity
session.close();
Session session = sessionFactory.openSession();
session.update(p); //reattach the detached entity
session.saveOrUpdate(p);
session.close();