How to make entities read-only after database insertion

hixson · **Joined:** Thu Sep 16, 2004 8:14 pm **Posts:** 27

Hibernate version: 3.2.5 GA

I have a number of entities that need to be capable of adding new rows of data to the database, but after insertion those rows must never be updated again. Is there a way to enforce this with annotations or other Hibernate configuration?
Thanks.

bahadir.konu · **Posted:** Sat Dec 15, 2007 8:01 am

Maybe we can understand the question more clearly if you tell:

- What are those entities that need to be capable of adding rows? Aren't these rows correspond to other entities? What are those rows about? Why they should not be updated?

- Did you try enforcing a business rule in your domain model which would be totally independent of the underlying persistence mechanism?

malm66 · **Joined:** Sat Nov 25, 2006 11:37 am **Posts:** 72

I don't think you can label an Entity as insert only. However you can annotate all your columns as updatable=false, e.g.

@Column(
name = "...",
updatable = false
)
public ... get...(...) { ... }

This should give your nearly the effect you wanted.

Note that the above refers to JPA annotations not Hibernate annotations.

hixson · **Joined:** Thu Sep 16, 2004 8:14 pm **Posts:** 27

Annotating the getter with that annotation does prevent the entity from being updated, but it doesn't appear to cause any kind of exception to be thrown. I'd like an exception to be thrown so that the developer is aware that they are attempting to do something that they should not. Right now it would be easy to assume that the update to the entity had succeeded without checking the database.
Is there anything I can do to get an exception thrown?
Thanks.

malm66 · **Joined:** Sat Nov 25, 2006 11:37 am **Posts:** 72

What about adding a @PreUpdate (and @PreRemove) callback method to your entity which throws an unchecked exception like:

Code:

@PreUpdate
private preUpdate() {
     throw new IllegalStateException("You are being very naughty!")
}

[/code]

hixson · **Joined:** Thu Sep 16, 2004 8:14 pm **Posts:** 27

I tried adding @PreRemove and a

public void preRemove() method as suggested and nothing happens when I call a setter on the entity. Is there something else I need to do?
Thanks.

malm66 · **Joined:** Sat Nov 25, 2006 11:37 am **Posts:** 72

The @PreUpdate and @PreRemove are only called just before the persistence runtime issues the SQL update or delete statement. They are not called when setters are invoked.

If all you want to do is stopping clients of your entity to call the setters then just make them private.

malm66 · **Joined:** Sat Nov 25, 2006 11:37 am **Posts:** 72

Sorry, you may say then users cannot create new entities as they can't populate them.

Solution 1) Give them a constructor which has arguments for all fields. This is part of the standard OO solution if you want to make an object immutable.

Solution 2) Use a @PostLoad and @PostPersist callback which sets a local boolean field and in all your setters test that field. If its true throw an exception.

Code:

private boolean locked = false;

@PostLoad 
@PostPersist
private void postLoad() { locked = true; }

public void set...(...) { if (locked) throw new ...; ...}