Join example for JPA finder

The JPA finder for play 2 works with joins as well.

Imagine you have a Task model with a creator:

@Entity(name = "tasks")
public class Task extends Model {
    @ManyToOne
    public User creator;
}

referenced to a User model with a name:

@Entity(name = "users")
public class User extends Model< User> {
    public String name;
}

You can write a method to get all Task for a creator username by joining on creator and access the user fields with the creator.field syntax:

public static List< Task> findByCreatorName(String creatorName){
   return Task.query().join("creator").eq("creator.name", creatorName).findList();
}

The source code for this example with unit tests is pushed to Play4Jpa