How to make an Entity read-only?

Question

What is the proper way to make an Entity read-only with JPA ? I wish my database table to never be modified at all programmatically.

I think I understand that I should lock my objects with LockModeType.READ. Is it possible to use an annotation to make my entities directly locked after retrieval from the database ? Or do I have to mess around and override my generic DAO for that specific entity ?

Answer 1

In your entity add an EntityListener like this:

@Entity @EntityListeners(PreventAnyUpdate.class) public class YourEntity {     // ... } 

Implement your EntityListener, to throw an exception if any update occurs:

public class PreventAnyUpdate {      @PrePersist     void onPrePersist(Object o) {         throw new IllegalStateException("JPA is trying to persist an entity of type " + (o == null ? "null" : o.getClass()));     }      @PreUpdate     void onPreUpdate(Object o) {         throw new IllegalStateException("JPA is trying to update an entity of type " + (o == null ? "null" : o.getClass()));     }      @PreRemove     void onPreRemove(Object o) {         throw new IllegalStateException("JPA is trying to remove an entity of type " + (o == null ? "null" : o.getClass()));     } } 

This will create a bullet proof safety net for your entity with JPA lifecycle listeners.

• PRO: JPA standard - not hibernate specific
• PRO: very safe
• CON: only shows write attempts at runtime. If you want a compile time check, you should not implement setters.