How do you get equals() working with Hibernate entities when lazy=true?

Question

For some reason when lazy=true on all my entities, the equals() method does not work correctly when one side is a lazily-loaded entity and the other side is a normal entity. Here's an example:

if(activeTask.getTask().equals(task)) {...}

In this case, the activeTask's task will be a proxy while the right side will be a regular one. The equals() will fail. To fix this problem, I often do things like this:

if(activeTask.getTask().getId() == task.getId()) {...}

This works, but it's not ideal. I'd rather use my equals() method.

Does anyone have a nice solution to this problem? It really adds to the application's level of noise to have to think about stuff like this.

If I say lazy=false, I don't have to deal with proxy's, and so equals() will work. But this has a very negative impact on performance.

It is just not cool to have to say, "equals() works in all cases, except when you use proxies... then equals() is not reliable."

Answer 1

I realize this is an old question, but it's still unanswered and people might stumble upon it.

I had the same problem a few days ago. In the project we use an abstract base class BasicEntityType, which has just an ID and equals is implemented in said base class:

@Override
public final boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }

    if (obj == null) {
        return false;
    }

    Class<?> objClass = HibernateProxyHelper.getClassWithoutInitializingProxy(obj);
    if (this.getClass() != objClass) {
        return false;
    }

    if (id == null) {
        return false;
    }

    return id.equals(((BasicEntityType) obj).getId());
}

There are two critical parts in this code:

• First: Do not check directly for class equality, it might not work with the given object.
• Second: All properties of the given object have to be accessed by using methods. Or you could unwrap the actual object.