在Hibernate中持久化LinkedList

Question

I am trying to persist a Class with a LinkedList Attribute but can't seem to get it right. Here is my code and my mapping:

 import java.util.LinkedList;
 public class Stuff implements java.io.Serializable {
    private long id;
private LinkedList<Image> images;


public Stuff() {
}


public Stuff(long Id) {
    id = Id;
}

public long getId() {
    return id;
}

public void setId(long mealId) {
    id = mealId;
}


public LinkedList<Image> getNumberImages(int number) {
    assert (number >= 0);
    return (LinkedList<Image>) images.subList(0, number) ;
}

public LinkedList<Image> getImages() {
    return images;
}
    public LinkedList<Image> setImages(LinkedList<Image> images) {
    this.images = images;
}


public void addImage(Image image) {
    if (!images.contains(image)) {
        images.add(image);
    }
}

Hibernate mapping:

<hibernate-mapping>
    <class name="data.Stuff" table="Stuff">
        <id name="id" type="long" access="field">
            <column name="ID" />
            <generator class="assigned" />
        </id>
        <list name="images" inverse="false" table="IMAGE" lazy="true" access="field">
            <key>
                <column name="ID" />
            </key>
            <list-index></list-index>
            <one-to-many class="data.Image" />
        </list>
    </class>
</hibernate-mapping>

It seems I can persist objects of the Class Stuff like this but when I try to recover them the following error occurres :

Hibernate: select stuff0_.ID as ID0_, stuff0_.NAME as NAME0_, meal0_.GROUPING as GROUPING0_ from MEAL meal0_
org.hibernate.PropertyAccessException: could not set a field value by reflection setter of data.Meal.images

Answer 1

Generally, Hibernate will provide its own implementations for collections so you should prefer interfaces to specific implementations. It's probably attempting to assign a different kind of list to images and failing. You would have to change your field to List<Image> .

Answer 2

Hibernate (and JPA in general) persists collections using their interfaces. The list must be declared as a List , and not as a LinkedList . And it won't be loaded with a LinkedList instance, because Hibernate uses its own List implementation to implement dirty-checking, lazy-loading, etc.

It's a good practice to program on interfaces rather than programming on concrete implementations in general. In JPA entities, it's mandatory.