CODEWITHSUNDEEP
google-app-enginejpa
Bendik
Bendik

Reputation: 217

App Engine JPA Entity relationships

I'm new to App Engine and trying to figure out how to use relationships between entities. I'm using JPA and having trouble to understand how to organize the relationships.

I have three classes City, Hotel and Attraction. I want cities to be standalone and able to be created on it's own. Every city has a list of all available hotels in the city. The hotel always need a city and can only have one city. Attractions have to have a city, but a city doesn't need to know about the attractions.

Classes:

 @Entity(name = "City")
 public class City {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @OneToMany(??)
    private List<Hotel> hotels;


    //getters and setters
}

@Entity(name = "Hotel")
public class Hotel {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Key key;

  private String name;

  @ManyToOne(??)
  private City city;
}


@Entity(name = "Attraction")
public class Attraction {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String name;

  @Unowned??
  private City city;

  //getters and setters
}

I've been looking all over the web, but i can't find any good tutorials on this. Would really appreciate any pointers in the right direction!

Upvotes: 1

Views: 282

Answers (1)

mastercoder
mastercoder

Reputation: 136

There is series of posts - "JDO/JPA Snippets That Work" on appengine java google group, which is a good starting point.

This one shows how to create a bidirectional, owned, one-to-many relationship.

Upvotes: 1

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