Java/LDAP: getAttribute(“cn”) returns null

Question

After a search in LDAP, written in Java, I have a valid entry as

cn=DE9-M5T,ou=students,ou=users,o=data

When I now do

if (entry != null && entry.getAttribute("modifyTimestamp") != null) {
         String dn = entry.getDN();
         String modifyTimestamp = entry.getAttribute("modifyTimestamp").getStringValue();
         String oldTimestamp = modificationTimestampCache.get(dn);

         String cnUserId = entry.getAttribute("cn").getStringValue(); 
         ...
 }

the last line gives a NullPointerException, which means that

entry.getAttribute("cn")

must return null . Following the documentation, this would only happen if the given attribute (here "cn" ) could not be found as exact match. Is there any reason that this could happen for "cn" in LDAP?

Answer 1

From your code I can't figure out the exact types of your entry and its getAttribute(), but consider this:

cn is a multivalued ldap attribute, where modifytimestamp is single valued.

So, the values of cn are probably stored in an array-like structure, I guess that your getAttribute() does not handle this as you expect.

Answer 2

Not every object class has a cn attribute. Only those where it appears in the schema.

Evidently this isn't one of them.