JPA Hibernate Lifecycle Callback Events Simple Explanation

Typical Entity Life-cycle

• Persist   - Creating Entity for the first time.
• Merge    - Saving detached Entity
• Load      - Loading Entity from Database
• Delete    - Deleting Entity from Database

JPA provides total of 6 Annotations for Life-Cycle Callback events.

1. @PrePersist
2. @PostPersist
3. @PreUpdate
4. @PostUpdate
5. @PreRemove
6. @PostLoad

This is how we can use the above annotations.

Solution 1: Defining inside Entity class

Any method can be annotated with one or all annotations, though they should follow these rules.

1.  Method can have any name
2.  No parameters
3.  Return type of void
4.  Method should not be final or static
5.  No Checked exceptions should be thrown
6.  Any annotation can be only used on one method

Example Code Snippet - 1

@Entity
public class Employee implements Serializable {
...

@PrePersist
@PostPersist
@PreUpdate
@PostUpdate
@PreRemove
@PostLoad
public void updateDate() {
    // this method will executed on all the lifecycle events.
}
}

Solution 2 : Using Entity Listeners Classes
This is very nice way of using the annotations. Clean code and same rules from above applies.

Example Code Snippet - 2


@EntityListeners({LastAccessDateListener.class})
public class Employee implements NamedEntity {
...
}

public class LastAccessDateListener {
@PrePersist
@PostPersist
@PreUpdate
@PostUpdate
@PreRemove
@PostLoad
public void updateDate(Employee e) {
  // this method is in totally separate class
}

}

LastAccessDateListener class doesn't have to be annotated or extend any other class.