src/main/java/com/googlecode/objectify/Ref.java
final public T safe() throws NotFoundException {
		T t = this.get();
		if (t == null)
			throw new NotFoundException(key());
		else
			return t;
	}
final public T safe() throws NotFoundException {
		T t = this.get();
		if (t == null)
			throw new NotFoundException(key());
		else
			return t;
	}
Obtain the entity value, throwing an exception if the entity was not found.

@return the entity referenced. Never returns null.
@throws NotFoundException if the specified entity was not found