1

Let's say I have Person and Order entities in a uni-directional, one-to-many relationship.

Person

@Entity
public class Person {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @OneToMany(mappedBy = "person")
  Set<Order> orders = new HashSet<Order>();

  // other fields, constructor, setters and getters

}

Order

@Entity
public class Order {

  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @Column(name = "id")
  Person person;

  // other fields, constructor, setters and getters
}

How can I update a Person's Set<Order> with new Order's?

Do I need to do something like:

Order o = new Order();
// ???

person.setOrders(new HashSet<Order>(o));

Since Person has a OneToMany relationship with Order's, I'm not sure how to set a Person's orders.

Kevin Meredith
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2 Answers2

2

Let's say I have Person and Order entities in a uni-directional, one-to-many relationship.

But your mappings suggests otherwise. It's bidirectional relationship with Order class (non-inverse side) having the responsibility of maintaining the relation.

If the relation is bidirectional with Order as non-inverse side, only setting person in Order should be sufficient to reflect the relation in database.

order.setPerson(person);

Although it is highly recommended that you set the Orders in Person as well so that your in-memory representation is consistent with the bidirectional nature of relation. Also recommended is to provide an "adder" method in Person instead of "set" which sets both ends of relationship at one place. For e.g.,

addOrders(Order order){
        this.orders.add(order);
        order.setPerson(this);
}

Also if you want to actually implement unidirectional one to many you may want to read this discussion.

Community
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Shailendra
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  • Hi - thanks for your answer. Conceptually, it seems to me that I only need a uni-directional relationship (`Person` to `Order`). What are your thoughts? – Kevin Meredith Jul 08 '14 at 21:37
  • I think this should be driven by the direction of navigation you are interested in your domain. In relational database all relations driven by foreign keys are navigable both ways, however in Object model you may decide to restrict access from one side – Shailendra Jul 11 '14 at 07:07
1

You can do something like this:

person1.getOrder().add(order1);

order1.setPerson(person1);

person1.getOrder().add(order2);

order2.setPerson(person1);

You can use this in loop for multiple orders

user3790568
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