Problem with lazy initial

[Nafanya]

Hello. My application build with Spring roo.

First class:

@RooJavaBean
@RooToString
@RooEntity
public class Detecter {

    @NotNull
    private String name;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Pictures> pics = new LinkedList<Pictures>();
}

Second class:

@RooJavaBean
@RooToString
@RooEntity
public class Pictures {

    @NotNull
    private String code;
}

in the class Detecter i set parameter Lazy in field :: pics::

I did it for not taking from database extra data. But in some case i need to take all related data.
I do not how realize this choose. Give me some advice on this issue.

P.S. Sorry for my bad English.

Truly yours, Nafanya.

[dr_pompeii]

Hello

I am confused with your case, first of all lets think about ORM only

Seems your relation configuration is wrong, have you read the Hibernate documentation?

1) Is better use a Set<Pictures> instead of List<Pictures>, because Set avoid duplication of Items within the collection
2) The Pictures class should has a relation with Detecter to receive its PK like a FK
3) Is better declare the class in singular, I mean only Picture
4) What error you have received? Could you post your complete error stack trace?

[Nafanya]

Answer your questions:

1. I use the LinkedList for two reasons:

1.1 In HashSet each item added to the random position in set;
1.2 LinkedList has more features than the HashSet.

2. I do not understand what mean phrase "to receive its PK like a FK";(primary key like foreign key?)
3. Ok. Thank you;
4.

2012-04-06 13:06:35,125 [main] ERROR org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: ru.me.Detecter.pictures, no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: ru.me.Detecter.pictures, no session or session was closed
	at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383)
	at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375)
	at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368)
	at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111)
	at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:272)
	at MainClass.<init>(MainClass.java:38)
	at MainClass.main(MainClass.java:46)
Exception in thread "main" org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: ru.me.Detecter.pictures, no session or session was closed
	at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383)
	at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375)
	at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368)
	at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111)
	at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:272)
	at MainClass.<init>(MainClass.java:38)
	at MainClass.main(MainClass.java:46)

[Marten Deinum]

You don't use a LinkedList as that is being replaced by a hibernate specific List implementation as soon as it becomes a managed object.

Have you actually read the stacktrace? You retrieve an object,probably through a transactional service method, after that the session and transaction is gone.

I suggest a forum search as questions regarding lazy loading have been answered numerous times before.

[Nafanya]

I agree with You. method to obtain the properties of entities (like detecter.getPictures()) called after the close of the session. I have read many articles on this issue on this and another forum. I understand I need to extend the session.
but I did not understand how to do it.

P.S. I develop a desktop application.