JPA lifecycle events practice
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This document discusses JPA lifecycle events and callback methods. It provides details on the different callback methods like @PrePersist, @PostPersist, etc. and describes what they are used for. It also discusses using entity listeners to attach listener classes to entities to handle lifecycle events. Multiple listener classes can be attached to a single entity class. The example shows using callbacks to automatically write user ID and timestamps to the database on inserts and updates.
JPA lifecycle events practice
- 2. Lifecycle Callbacks It is often necessary to perform various actions at different stages of a persistent object's lifecycle. JPA includes a variety of callbacks methods for monitoring changes in the lifecycle of your persistent objects. These callbacks can be defined on the persistent classes themselves and on non-persistent listener classes.
- 3. Callback Methods Callback method Description @PrePersist before a new entity is persisted (added to the EntityManager). @PostPersist after storing a new entity in the database (during commit or flush). @PostLoad after an entity has been retrieved from the database. @PreUpdate when an entity is identified as modified by the EntityManager. @PostUpdate after updating an entity in the database (during commit or flush). @PreRemove when an entity is marked for removal in the EntityManager. @PostRemove after deleting an entity from the database (during commit or flush).
- 5. Using Entity Listeners The listener class is attached to the entity class using the @EntityListeners annotation Multiple listener classes can also be attached to one entity class
- 6. Example
- 7. NIG005W User uses this function to maintain organization information.
- 8. Schema We intend to utilize JPA callback method to write user id and update timestamp into database automatically to ease programmers’ efforts.
- 9. Using Callback Methods Multiple events can be assigned to a single method as well. This method Will be triggered before insert and update.
- 10. Using Entity Listeners Mixing lifecycle event code into your persistent classes is not always ideal. It is often more elegant to handle cross-cutting lifecycle events in a non-persistent listener class. JPA allows for this, requiring only that listener classes have a public no-arg constructor. Like persistent classes, your listener classes can consume any number of callbacks. The callback methods must take in a single java.lang.Object argument which represents the persistent object that triggered the event.