Question

How can I map a map?

I have this:

private Map<Integer, Trip> trips = new HashMap<Integer, Trip>();

As mapkey I want the trip id..

The Trip entity is holding the reference to my entity. (the column is in another table).
The trip has a column to my reference id.

How can I do that?

Something like

@MapKeyTable(name="trips")
@MapKeyColumn(name="trip_id")
@OneToMany(joinTable......)
private Map<Integer, Trip> trips = new HashMap<Integer, Trip>();

Answer 1

If trip id is a property of Trip (say tripId), then you need the following:

@MapKey(name = "tripId")
@OneToMany(...)
private Map<Integer, Trip> trips = new HashMap<Integer, Trip>();

Other annotations are for more complex cases.