Hibernate Mapping Help!

Question

I am quite new to Hibernate so I am not entirely sure if what I want to do is even possible (or the right thing to do) so if it is not, feel free to suggest other ways of achieving what I am looking for.

I have 2 entities, Competition and Fixture. There is a One-to-Many relationship between them. I know how to set up the annotations to achieve this, but what I am struggling with is making the relationship bidirectional. If my application were to run for a long time, the number of Fixtures belonging to a competition would build up. The most common way I will be accessing the Fixture objects is via a Competition by specifying a particular date (e.g. getFixtures(today)). I thought I could implement this by having a Map in the Competition class that maps the date of the Fixture to a collection of Fixtures for that date. I have no idea how to set this up in Hibernate though.

Here is a simplified set of POJOs and Annotations that illustrate what I have so far:

@Entity
public class Competition {

    // This is what I would like to have.
    private Map<Date, Collection<Fixture>> fixtureMap;

    public Collection<Fixture> getFixtures(Date day) {
        return fixtureMap.get(day);
    }

    // This is all I know how to do.
    private Collection<Fixture> fixtureList;

    @OneToMany(mappedBy = "competition")
    public Collection<Fixture> getFixtureList() {
        return fixtureList;
    }
}

@Entity
public class Fixture {

    private Competition competition;

    @ManyToOne
    public Competition getCompetition() {
        return competition;
    }
}

As you can see from this I can set the relationship up to access the entire set of Fixtures for a competition. But to get the Fixtures for a specific day I would have to iterate over the entire collection of Fixtures and check the dates of each. Is there any way I can get Hibernate to handle the mapping from Date to a Collection of Fixtures? If I could do that then I would be able to simply access the collection of Fixtures for that day using the Date as the key in the Map.

Answer 1

No direct annotation can help. You will have to write a query for fetching fixtures of particular date.

Answer 2

I believe you can use Hibernate Entity Maps. The following thread will be useful: How to persist Map with Annotations You can also lookup Entity Map on the Hibernate Cheatsheet

Answer 3

@Entity
public class Competition 
{
   private Map<Date, Collection<Fixture>> fixtureMap;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "competition")
    @MapKey("date")
    public Collection<Fixture> getFixtures(Date day) 
    {
        return fixtureMap.get(day);
    } 
}

@Entity
public class Fixture 
{

    private Competition competition;

    private Date date;

    @Column(name="FIXTURE_DATE")
    public Date getDate() 
    {
        return date;
    }

    @ManyToOne
    public Competition getCompetition() 
    {
        return competition;
    }
}

Remember to setup the bi-directional relationships before saving the Competition object. Meaning you have to set the competition object within fixture to persist the fixture object and the relationship.