Hi All,

Has anyone experienced this? I have a class AppInstance that contains a private variable of type "Set".

private java.util.Set objectSet;

The problem is, when I save a set of multiple objects into a class instance, and then retrieve that set, I retrieve ONLY the first element of that set. For example, set size is only 1.

appInstance.getObjectSet().getSize() is equal to 1 only!

The set is supposed to contain objects of another class that I defined, let's say app2instance objects. Here is my mapping in the hibernate mapping file (app2contentSet is my objectSet variable):

<set
inverse="true"
lazy="false"
name="app2contentSet"
cascade="all"
sort="com.tivella.xtas.application.data.hibernate.application.AppToContentComparator"
>
<key column="app_instance_id" />
<one-to-many class="App2content" />
</set>


The funny thing is that the database saves ALL values that is stored into the Set variable. There seems to be a problem with the retrieval. I assume saving works because the database has the correct data. Does anyone have any suggestions? Please let me know if you need more details. Thanks for listening.

- Joseph
UCLA

Do you see the values in DB? Do you have an equal method on the App2Content class? how is the comparator key? Turn on the sql output and see what happens after retrieval point.



Farzad-

Thanks for the reply.

1) The values in the database are indeed correct. The Set commits all values to the database, not just one.

2) There is an equals class in my app2content:

public boolean equals (Object obj) {
if (null == obj) return false;
if (!(obj instanceof com.tivella.xtas.application.data.hibernate.application.App2content)) return false;
else {
com.tivella.xtas.application.data.hibernate.application.App2content app2content = (com.tivella.xtas.application.data.hibernate.application.App2content) obj;
if (null == this.getId() || null == app2content.getId()) return false;
else return (this.getId().equals(app2content.getId()));
}
}


3) I am not sure what a comparator key is but here is the comparator class if it helps:

public class AppToContentComparator implements Comparator {

protected final static Logger logger = Logger.getLogger( AppToContentComparator.class );
protected boolean isFirstTime = true;
protected Comparator actualComparator = null;

/* (non-Javadoc)
* @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
*/
public int compare(Object o1, Object o2) {

if ( isFirstTime ) {
String cn = o1.getClass().getName() + "Comparator";
try {
Class cl = Class.forName( cn );
actualComparator = (Comparator)cl.newInstance();
}
catch ( Exception e ) {
logger.error( e.getMessage() );
}
}
int res = 0;
if ( actualComparator != null )
res = actualComparator.compare( o1, o2 );

isFirstTime = false;

return res;
}

}

Try implementing hashCode() as as well as equals().
Just return the hashCode of your id or 1 if the id is null.

hm strange. hashCode() and equals() are already implemented.

public int hashCode () {
if (Integer.MIN_VALUE == this.hashCode) {
if (null == this.getId()) return super.hashCode();
else {
String hashStr = this.getClass().getName() + ":" + this.getId().hashCode();
this.hashCode = hashStr.hashCode();
}
}
return this.hashCode;
}

notice that hashCode and equals do not use the same criteria for establishing equality (hashCode is involving the name also). That might be your problem, which would be a Java problem.
The relationship between equals() and hashCode() is as follows:



The opposite doesn't need to be true, though. Try leaving equals() as it is and returning always 1 from hashcode, and check what happens.

I'm assuming the getId() method returns the database identifier?
If so, this is really not a good candidate for implementing equals() and hashCode().
Read this for more information.

Hm...Hashcode() returning 1 does not seem to change behavior.

In the database table, there is an Id column that is the primary key for each row. If that is what you mean by the database identifier, then yes. Though, I think Hibernate should abstract that, no? Well in any case, I'm reading the link you sent and trying it out. Thanks for the info.