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Wednesday March 26, 2003

Hibernate: Comparing Objects

I'm having an interesting problem with Hibernate this morning, hopefully you can offer some assistance. Basically, I have an object called Parent that has a property called Kids. The List of Kids is set the from UI on an update using indexed properties. My UI is somewhat dynamic in that kids can be removed from the table using JavaScript - and then this record is not passed in via the request. My update works just fine, however, these deleted kids need to be removed from the database.

My initial solution was to (using Hibernate) get a list of the existing kids for the parent after the updates/inserts had occurred: 

List dbKids = 
    ses.find("from k in class " + Kid.class
             + " where k.parentId=?", k.getParentId(), Hibernate.LONG);

if (!parent.getKids.containsAll(dbKids)) {
    // loop through the dbKids and delete ones not not passed in
    for (int i = 0; i < dbKids.size(); i++) {
        Kid kid = (Kid) dbKids.get(i);
        if (!parent.getKids().contains(kid)) {
            ses.delete(kid);
        }
    }
}

The problem I'm having is that my kids that are passed in (parent.getKids()) contain empty Strings for their null String properties. This (I'm assuming) is done by BeanUtils.copyProperties(). However, the kids in dbKids contain null for their null properties. Any ideas/suggestions are appreciated. I'll try digging into BeanUtil.copyProperties() and see if I can solve it there.

Posted in Java at Mar 26 2003, 10:11:05 AM MST 2 Comments
Comments:

Do your equals() and hashcode() method use these fields? You might want to just make them use the unique identifier, instead. Then you don't have to worry about it, because it will be able to tell whether they're in there or not whether those fields are "" or null.

Posted by Jason Carreira on March 26, 2003 at 08:21 PM MST #

My equals() and hashCode() methods are from my BaseObject class: <code>public boolean equals(Object o) { &nbsp;&nbsp;return EqualsBuilder.reflectionEquals(this, o); } public int hashCode(Object o) { &nbsp;&nbsp;return HashCodeBuilder.reflectionHashCode(this); }</code> Good idea - I'll just override equals() in my Kid class to only have the primary keys. Thanks!

Posted by Matt Raible on March 26, 2003 at 08:52 PM MST #

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