OK, gave up on the mappedBy and went for joincolumns and that seemed to work. Now for the next step, composite keys, I modifed the example as
The problem is that I'm trying to get it to work against a legacy schema and I have uses for the childOrder so I'd like it to be part of the key but I get a
even If I try to do so in the embedded key. Can't the column index be pointed against a column/property that is "non-synthetic"?