No default constructor for entity for inner class in Hibernate

If the class is not static, it requires an instance of the outer class in order to be instantiated - so there will be no default constructor. You'd have to use syntax similar to:

new Supply().new Id();

If the Id class is static, you can just call:

new Id();

I always add an empty protected constructor to the class to solve this issue like so:

protected Classname(){}

In your case it would look like this:

protected Id(){}