code: public Entry lookup(Dn dn) throws NoSuchNodeException, MissingParentException {
          existsCheck(dn);
          try {
              return connection.lookup(dn);
          } catch (LdapException e) {
              throw new LdapDaoException(e);
          }
      }
docs: Returns the {@link Entry} with given {@link Dn}. If dn does not exist but its parent does, a
  {@link NoSuchNodeException} is thrown. If one of dn's ancestors does not exist, a {@link MissingParentException}
  is thrown.