OpenDJ SDK Developer's Guide
Chapter 10. Working With Controls

RFC 3672, Subentries in LDAP, describes subentries and also the subentries request control. When you perform a search without the control and visibility set to TRUE, subentries are only visible in searches with SearchScope.BASE_OBJECT.

if (isSupported(SubentriesRequestControl.OID)) {
    final SearchRequest request =
            Requests.newSearchRequest("dc=example,dc=com",
                        SearchScope.WHOLE_SUBTREE,
                        "cn=*Class of Service", "cn", "subtreeSpecification")
                    .addControl(SubentriesRequestControl.newControl(
                        true, true));

    final ConnectionEntryReader reader = connection.search(request);
    final LDIFEntryWriter writer = new LDIFEntryWriter(System.out);
    try {
        while (reader.hasNext()) {
            if (reader.isEntry()) {
                final SearchResultEntry entry = reader.readEntry();
                writer.writeEntry(entry);
            }
        }
        writer.close();
    } catch (final ErrorResultIOException e) {
        // Request failed due to an IO problem.
    } catch (final SearchResultReferenceIOException e) {
        // Read a reference, rather than an entry.
    } catch (final IOException e) {
        // The writer could not write to System.out.
    }
}

OpenDJ directory server supports the control.

dn: cn=Bronze Class of Service,dc=example,dc=com
cn: Bronze Class of Service
subtreeSpecification: { base "ou=People", specificationFilter "(classOfService=
 bronze)" }

dn: cn=Silver Class of Service,dc=example,dc=com
cn: Silver Class of Service
subtreeSpecification: { base "ou=People", specificationFilter "(classOfService=
 silver)" }

dn: cn=Gold Class of Service,dc=example,dc=com
cn: Gold Class of Service
subtreeSpecification: { base "ou=People", specificationFilter "(classOfService=
 gold)" }