Hibernate Annotations with a collection

I am trying to implement my model using hibernate annotations. I have 3 classes, image, person, and tags. Tags is a a table consisting of 4 fields, an id, personId, imageId, and a createdDate. Person has the fields name, id, birthdate, etc. My image class is defined as follows:

@Entity
@Table(name="Image")
public class Image {
    private Integer imageId;
    private  Set<Person> persons = new HashSet<Person>();

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "ID")
    public Integer getImageId() {
        return imageId;
    }

    public void setImageId(Integer imageId) {
        this.imageId = imageId;
    }

    @ManyToMany
    @JoinTable(name="Tags",
                joinColumns = {@JoinColumn(name="imageId", nullable=false)},
                inverseJoinColumns = {@JoinColumn(name="personId", nullable=false)})
    public Set<Person> getPersons() {
        return persons;
    }

    public void setPersons(Set<Person> persons) {
        this.persons = persons;
    }

If I remove the annotations on the getPersons() method I can use the classes and add and remove records. I want to fetch all the tags with the image and I am trying to use a set. I开发者_如何学C keep getting the following error:

org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: com.exmaple.persons, no session or session was closed

Can someone please help me and let me know what I am doing wrong?

Thank you

This error message - which actually has nothing to do with your association mapping strategy or annotations - means that you have attempted to access a lazy-loaded collection on one of your domain objects after the Session was closed.

The solution is to either disable lazy-loading for this collection, explicitly load the collection before the Session is closed (for example, by calling foo.getBars().size()), or making sure that the Session stays open until it is no longer needed.

If you are not sure what lazy-loading is, here is the section in the Hibernate manual.

Thanks for the response matt. I am confused now. My query to retrieve the image looks like this:

public Image findByImageId(Integer imageId) {
    @SuppressWarnings("unchecked")
    List<Image> images = hibernateTemplate.find(
            "from Image where imageId=?", imageId);
    return (Image)images.get(0);
}

I thought that I can call the single hql query and if my mappings are correct it will bring back the associated data.

I was looking at this example at this link hibernate mappings:

2.2.5.3.1.3. Unidirectional with join table
A unidirectional one to many with join table is much preferred. This association is described through an @JoinTable.

@Entity
public class Trainer {
    @OneToMany
    @JoinTable(
            name="TrainedMonkeys",
            joinColumns = @JoinColumn( name="trainer_id"),
            inverseJoinColumns = @JoinColumn( name="monkey_id")
    )
    public Set<Monkey> getTrainedMonkeys() {
    ...
}

@Entity
public class Monkey {
    ... //no bidir
}         Trainer describes a unidirectional relationship with Monkey using the join table TrainedMonkeys, with a foreign key trainer_id to Trainer (joinColumns) and a foreign key monkey_id to Monkey (inversejoinColumns).