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Query to filter collection [message #809095]

Tue, 28 February 2012 13:29

Pavel Zelenka

Messages: 61
Registered: July 2009

Member

Hi,

I would appreciate any advice with this problem:

Let's assume I have two entities: Order and Item (one order can contain number of items)

@Entity
public class Order
@Id
@Column(name = "order_id")
private Integer orderId;
@Column(name = "order_date")
@Temporal(TemporalType.DATE)
private Date orderDate
@OneToMany(mappedBy = "order", cascade = CascadeType.ALL)
private List<Item> itemList
....

@Entity
public class Item
@Id
@Column(name = "item_id")
private Integer itemId;
@Column(name="item_text")
private String itemText;
@Column(name="item_value")
private Integer itemValue;
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "order_id", referencedColumnName = "order_id")
private Order order
....

I want to select orders which contains items where item value=100. But I want to Order.itemList to be filled only with items of value 100.

Is this possible (EclipseLink 1.1.4, Tomcat 6)

Thanks

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Re: Query to filter collection [message #809320 is a reply to message #809095]

Tue, 28 February 2012 18:38

Chris Delahunt

Messages: 1364
Registered: July 2009

Senior Member

Not with JPA. JPA requires that entities returned from the EntityManager be managed, and so should reflect the data as it exists in the database. Only partially populating the itemList collection can leave the entity corrupt in the cache - on the next query when you want all items you will still only see items in the itemList that met your filter criteria.

It can be done, but I wouldn't recommend adding filter logic to the mapppings that the application can easily do itself when required. For instance, you can easily query for all items with value=100 and join it to Order so you have a list of items so itemList doesn't need to be accessed. ie "Select item From Item item Fetch Join item.order Where item.value=100".

Regards,
Chris

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