Improve the exception message in the PojoInstantiator class if the class is abstract

[YassinHajaj]

Hi,

When using @Inheritance(strategy = InheritanceType.JOINED) without mapping all subclasses tables in the application, Hibernate will try to instantiate the abstract class, which will not work and throw an exception.

The following method is the one that throws the error (line 3).

	public Object instantiate() {
		if ( isAbstract ) {
			throw new InstantiationException( "Cannot instantiate abstract class or interface: ", mappedClass );
		}
		else if ( optimizer != null ) {
			return optimizer.newInstance();
		}
		else if ( constructor == null ) {
			throw new InstantiationException( "No default constructor for entity: ", mappedClass );
		}
		else {
			try {
				return applyInterception( constructor.newInstance( (Object[]) null ) );
			}
			catch ( Exception e ) {
				throw new InstantiationException( "Could not instantiate entity: ", mappedClass, e );
			}
		}
	}

The message is clear, but at the same time, it doesn't give enough insight about why it tries to instantiate an abstract class.

Can it give more hints like "Have you mapped all entities depending on this abstract class?" or something alike ?

Not to mention that enabling DEBUG mode didn't help neither.

This would avoid precious minutes of debugging 😄.

[beikov]

This is not the place to ask question. See #7522, #3767 and #4723