JPA/Hibernate + get specific item from onetomayrelation

I want to get a开发者_StackOverflow中文版 specific row in a OneToMany relation. E.g. getting the cheapest item of an order

Example:

public class Order {

 @Id
 @Column(name = "ORDER_ID")
 private Long id;

 ???
 private Item cheapestItem;

}

public class Item {

 @Id
 @Column(name = "ITEM_ID")
 private Long id;

 private Long price;

}

How can I do this?

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Try specifying a where clause in the hibernate @Where annotation (Not sure if you can apply it to a non-collection, though)

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I want to get (...) the cheapest item of an order

If you really want to get the cheapest Item (without actually persisting it), it should be is doable with a ManyToOne and a JoinColumnOrFormula. Requires Hibernate 3.5+, see issues like HHH-4382 and HHH-5041 for examples.

Retrieving only the price would be much easier and doable with previous versions of Hibernate. See Hibernate Derived Properties - Performance and Portability.