code: @Override
      protected String appendAttributeToQuery(final String queryBuilder, final String dataAttribute, final List<Object> queryValues) {
          if (queryBuilder != null) {
              return queryBuilder;
          }
  
          final String keyAttributeName;
          if (this.queryAttributeName != null) {
              keyAttributeName = this.queryAttributeName;
          } else {
              final IUsernameAttributeProvider usernameAttributeProvider = this.getUsernameAttributeProvider();
              keyAttributeName = usernameAttributeProvider.getUsernameAttribute();
          }
  
          if (keyAttributeName.equals(dataAttribute)) {
              return String.valueOf(queryValues.get(0));
          }
  
          return null;
      }
docs: /* (non-Javadoc)
  @see org.jasig.services.persondir.support.AbstractQueryPersonAttributeDao#appendAttributeToQuery(java.lang.Object, java.lang.String, java.util.List)