Hi,
I need to read a complex model in an ordered way with eclipselink. The
order is mandantory because it is a huge database and I want to have an output of a small portion of the database in a jface tableview. Trying to reorder it in the loading/quering thread takes too long and ordering it in the LabelProvider blocks the UI thread too much time, so I thought if Eclipselink could be used that way, that the database will
order it, it might give me the performance I need. Unfortunately the object model can not be changed :-(
The model is something like:
@SuppressWarnings("serial")
@Entity
public class Thing implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
private int id;
private String name;
@OneToMany(cascade=CascadeType.ALL)
@PrivateOwned
private List<Property> properties = new ArrayList<Property>();
...
// getter and setter following here
}
public class Property implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
private int id;
@OneToOne
private Item item;
private String value;
...
// getter and setter following here
}
public class Item implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
private int id;
private String name;
....
// getter and setter following here
}
// Code end
In the table view the y-axis is more or less created with the query
Query q = em.createQuery("SELECT m FROM Thing m
ORDER BY m.name ASC");
using the "name" attribute from the Thing objects as label.
In the table view the x-axis is more or less created with the query
Query q = em.createQuery("SELECT m FROM Item m
ORDER BY m.name ASC");
using the "name" attribute from the Item objects as label.
Each cell has the value
Things.getProperties().get[x].getValue()
Unfortunately the list "properties" is not ordered, so the combination of cell value and x-axis column number (x) is not necessarily correct. Therefore I need to
order the list "properties" in the same way as I ordered the labeling of the x-axis.
And exactly this is the thing I dont know how it is done. So querying for the Thing objects should return the list "properties" "
ORDER BY name ASC" but of the "Item"s objects. My ideas are something like having a query with two JOINs. Joing Things with Property and with Item but somehow I was unable to get it to work yet.
Thank you for your help and your ideas to solve this riddle.
