Differences Between session.save() and session.persist() in Hibernate

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问题:

What is the difference between session.save() and session.persist() method in Hibernate?

回答:

In Hibernate, both session.save() and session.persist() methods are used to make a transient object persistent, but there are some differences between them in terms of their behavior and usage. Here’s a breakdown of the differences:

1. Return Type:

  • session.save(): This method returns the identifier (primary key) of the newly saved entity. It returns a Serializable type, which is typically the type of the primary key.
  • session.persist(): This method does not return anything. It has a void return type.

2. Use Case:

  • session.save(): This method is typically used when you need to obtain the generated identifier immediately after saving the entity. It is often used in scenarios where you need to use the identifier for further processing.
  • session.persist(): This method is used when you do not need the identifier immediately. It is more aligned with the JPA specification and is often preferred in JPA-based applications.

3. Behavior:

  • session.save(): It can be used to save an entity in a way that it is immediately assigned an identifier. If the entity is already persistent, it will throw an exception.
  • session.persist(): It is more of a "hint" to the Hibernate session that the entity should be made persistent. If the entity is already persistent, it will not throw an exception; instead, it will simply ignore the call.

4. JPA Compliance:

  • session.save(): This method is specific to Hibernate and is not part of the JPA specification.
  • session.persist(): This method is part of the JPA specification, making it more portable across different JPA implementations.

Summary:

  • Use session.save() when you need the generated identifier and are working specifically with Hibernate.
  • Use session.persist() when you are following JPA standards and do not need the identifier immediately.

In general, if you are working in a JPA context, it is recommended to use persist() for better compatibility and adherence to the JPA specification.