How do I have a child table when the parent has a composite key

[Jayesh A Lalwani]

I am trying to model a set of tables that are very poorly designed. The problem is that I have a table with a composite key, and this table has some child tables. So, the tables look like this

Instrument
    instrumentID*
    batchID*
    .
    .

Payment
    instrumentID*
    batchID*
    paymentDate*
    .
    .

There is an Instrument table with a composite PK(instrument id and batchID) and a Payment table with a composite PK(instrument ID, batch ID and paymentDate) There is FK relationship between Payment and Instrument on instrumentID and batchID. For an Instrument there can be multiple Payments

My first inclination is to change the table to add proper sequence generated IDs, but doing so would impact a lot of legacy code. I might be able to do it, but if I can't, I wanted to see if there are any options to model the table as is in JPA

What I have now is this

@Embeddable
class InstrumentPK {
  String instrumentId;
  int batchID;

}
@Entity
class Instrument {
   @EmbeddedId
   InstrumentPK id;
   List<Payment> payments;
}

@Embeddable
class PaymentPK {
   Instrument instrument;
   Date paymentDate;
}
@Entity
class Payment {
   @EmbeddedId
   PaymentPK id;
   .
   .
   .
}

The problem is I can;t figure out how to put the Join annotations. I wanted to put OneToMany on Instrument.payments and ManytoOne on PaymentPK.instrument. However, how do I put multiple column names in the relationship?

[Vijitha Kumara]

You can do something like:

...
@JoinColumns({
@JoinColumn(),
@JoinColumn()
})