Mapping Hashmap of Coordinates in Hibernate with Annotation
I've just started using hibernate and I'm trying to map walking distance between two coordinates into a hashmap, There can be many connections from one "FromCoordinate" to another "ToCoordinate". I'm not sure if i've implemented this correctly, What annotations do i need to map this MashMap? Thanks
HashMap> coordWalkingConnections = new HashMap>();
@Entity
@Table(name = "COORDCONNECTIONS")
public class CoordinateConnection implements Serializable{
private static final long serialVersionUID = -1624745319005591573L;
/** auto increasing id number */
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "ID")
@id
private int id;
@Embedded
public FromCoordinate fromCoord;
@Embedded
public ToCoordinate toCoord;
HashMap<FromCoordinate, ArrayList<ToCoordinate >> coordWalkingConnections = new HashMap<FromCoordinate, ArrayList<ToCoordinate >>();
}
public class FromCoordinate implements ICoordinate
{
@Column(name = "FROM_LAT")
private double latitude;
@Column(name = "FROM_LNG")
private double longitude;
}
public class ToCoordinate implements ICoordinate
{
@Column(name = "TO_LAT")
private double latitude;
@Column(name = "TO_LNG")
private double longitude;
@Column(name = "DISTANCE")
private double distance;
}
DATABASE STRUCTURE
id FROM_LAT FROM_LNG TO_LAT TO_LNG Dist
1 43.352669 -6.264341 43.350012 -6.260653 0.38
2 43.352669 -6.264341 43.352669 -6.264341 0.00
3 46.352669 -6.264341 43.353373 -6.262013 0.17
4 47.352465 -6.265865 43.351290 -6.261200 0.25
5 45.452578 -6.265768 43.352788 -6.264396 0.01
6 45.452578 -6.265768 45.782788 开发者_JAVA技巧-6.234523 0.01
.....
...
.
Example HashMap for HashMap<Coordinate, ArrayList<Coordinate>>
<KEY{43.352669 -6.264341}, Arraylist VALUES{(43.350012,-6.260653,0.383657), (43.352669, -6.264341, 0.000095), (43.353373, -6.262013, 0.173201)}>
<KEY{47.352465 -6.265865}, Arraylist VALUES{(43.351290,-6.261200,0.258781)}>
<KEY{45.452578 -6.265768}, Arraylist VALUES{(43.352788,-6.264396,0.013726),(45.782788,-6.234523,0.017726)}>
Well in my opinion you have to use the interface type of collection in initialization.
Instead of:
HashMap<FromCoordinate, ArrayList<ToCoordinate >> coordWalkingConnections = new HashMap<FromCoordinate, ArrayList<ToCoordinate >>();
use:
Map<FromCoordinate, List<ToCoordinate >> coordWalkingConnections = new HashMap<FromCoordinate, ArrayList<ToCoordinate >>();
If you read the hibernate documentation at: http://docs.jboss.org/hibernate/core/3.3/reference/en/html/collections.html you will read:
The actual interface might be java.util.Set, java.util.Collection, java.util.List, java.util.Map, java.util.SortedSet, java.util.SortedMap or anything you like ("anything you like" means you will have to write an implementation of org.hibernate.usertype.UserCollectionType.)
Notice how the instance variable was initialized with an instance of HashSet. This is the best way to initialize collection valued properties of newly instantiated (non-persistent) instances. When you make the instance persistent, by calling persist() for example, Hibernate will actually replace the HashSet with an instance of Hibernate's own implementation of Set. Be aware of the following errors:
I do not know if this is the only error. Hope this would help you.
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