LDAP: Recommended way to add new objectclass to existing entries?

Question

Can anyone help me with the preferred way to add a new objectclass (with attrributes) to existing entries within a directory (via the javax.naming API)?
I have an application that uses a directory of users. Each user has objectclasses "top", "person", and "inetOrgPerson" with usual attributes.
The application needs to change to add a custom objectclass, say "ourAppClass" (and its attributes), to each existing entry within the directory. I have already successfully defined the schema for the objectclass within the directory.
I cannot find examples showing how to add an objectclass to existing entries. Creating brand new entries with custom objectclassess is straightforward.
When using DirContext.modifyAttributes must I define all the objectclasses again, or is there a way to send only the new objectclass and its attributes only?
Attributes attrs = new BasicAttributes();
Attribute classes = new BasicAttribute("objectclass");
classes.add("top");  // do I need these?
classes.add("person"); // do I need these?
classes.add("inetOrgPerson"); // do I need these?
classes.add("ourAppClass"); // in-house class
attrs.put(classes);
attrs.put("ourCustAtribute", "value1"); //
DirContext.modifyAttributes(dn, LdapContext.REPLACE_ATTRIBUTE, attrs);Does someone have a good example to follow?

Answer 1

I think I have answered my own question. I think I need to use a ModificationItem to add an attribute to the objectclass.
final ModificationItem[] classModification= new ModificationItem[1];
classModification[0] = new ModificationItem(DirContext.ADD_ATTRIBUTE,
            new BasicAttribute("objectclass", "ourAppClass"));
dirContext.modifyAttributes(dn, classModification);