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.
