Initializing POJO's generic Set

Trevor Stewart · **Joined:** Mon May 08, 2006 10:47 am **Posts:** 1

Hibernate version: 3.1.3

I'm trying to figure out how to initialize my POJO's generic Set property (it's children, if you will).

Here's the situation...

Class Parent is as follows (my apologies for syntax errors):

Code:

package x.y.foo;

public class Parent implements java.io.Serializable {

    static final long serialVersionUID = -123L;

    private String propertyA;
    private String propertyB;
    private Set setOfChildren;  //of type x.y.foo.Child

    public Parent() {
    }

    public void setPropertyA(String str) {
        this.propertyA = str;
    }

    public String getPropertyA() {
        return this.propertyA;
    }

    public void setPropertyB(String str) {
        this.propertyB = str;
    }

    public String getPropertyB() {
        return this.propertyB;
    }

    //  Of what concrete implementation must newSet be
    //   inorder for the Hibernate persistence to work?
    public void setSetOfChildren(Set newSet) {
        this.setOfChildren = newSet;
    }

    public Set getSetOfChildren() {
        return this.setOfChildren;
    }

    // Convenience Method
    public void addChildToSetOfChildren(Child child) {
        if (setOfChildren == null) {
            // I would like to initialize setOfChildren here
            //  BUT what concrete implementation should I use???
        }
        this.setOfChildren.add(child);
    }
}

In the example above I would like to know what concrete implementation of Set to use to initialize the Set of children.
I know that Hibernate is using org.hibernate.collection.PersistentSet and I can use this as well BUT that will then tightly
couple my POJO to a Hibernate implementation and I would like to avoid this if possible.

Thank you for your help.

r1ch · **Joined:** Wed Aug 25, 2004 6:23 am **Posts:** 91

You can use any type of set that you want when you create the object (I typically use a HashSet) but be aware that when you load the object back in Hibernate will recreate it with a PersistentSet so any special properties of the set that you used will be lost.

r1ch · **Joined:** Wed Aug 25, 2004 6:23 am **Posts:** 91

See here for a more complete explanation:- http://www.hibernate.org/hib_docs/v3/re ... persistent

max · **Posted:** Mon May 08, 2006 3:29 pm

and don't just do the check in the setter; you should also return a collection (not null) from the getter.