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pythedev

hibernate - one to many relationship in the same table.

0 posts in this topic

Hello!

I have a posgresql database where information about rivers are stored.

[CODE]
CREATE TABLE river_data
(
id_river integer,
id_destination integer,
river_name character varying(15),
... many other fields
)
WITH (
OIDS=FALSE
);
ALTER TABLE river_data
OWNER TO xyz;
[/CODE]

Getting information about one single river without its subrivers works well:

[CODE]
@Entity
@Table(name = "river_data")
public class RiverData {
@Id
@Column (name = "id_river")
private int riverId;
@Column (name = "river_name")
private String riverName;
@Column (name = "id_destination")
private int destinationRiverId;
public int getRiverId() {
return riverId;
}
public String getRiverName() {
return riverName;
}
public int getDestinationRiverId() {
return destinationRiverId;
}
}
[/CODE]

Now I want to retrieve information about a river with a list(collection) of its subrivers, but I don't know how. All subrivers should have their destination_id equal to the main river_id. The current code looks like this(it crashes the sql server):

[CODE]
@Entity
@Table(name = "river_data")
public class RiverDataWithSubRivers {
@Id
@Column (name = "id_river")
private int riverId;
@Column (name = "river_name")
private String riverName;
@Column (name = "id_destination")
private int destinationRiverId;
@OneToMany
@JoinColumn(name="id_destination") // TODO: problem is here.
private Collection<RiverData> subRivers= new ArrayList<RiverData>(10);
public Collection<RiverData> getSubRivers() {
return subRivers;
}
public int getRiverId() {
return riverId;
}
public void setRiverId(int riverId) {
this.riverId = riverId;
}
public String getRiverName() {
return riverName;
}
public void setRiverName(String riverName) {
this.riverName = riverName;
}
public int getDestinationRiverId() {
return destinationRiverId;
}
public void setDestinationRiverId(int destinationRiverId) {
this.destinationRiverId = destinationRiverId;
}
}
[/CODE]

The question is, what annotations and how should I use them in this part of code:

[CODE]
@OneToMany
@JoinColumn(name="id_destination") // TODO: problem is here.
private Collection<RiverData> subRivers= new ArrayList<RiverData>(10);
[/CODE]

My idea was that the @JoinColumn would help me to select all rivers, which have the same id_destination, that equal to the id_river of this class.
0

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