SQL2 search not giving results when executed from servlet for Vietnamese and Korean character set

SQL2 search not giving results when executed from servlet for Vietnamese and Korean character set.

We have set 

Apache Sling request parameter handling - Default Parameter Encoding - to UTF-8

When we hit the servlet which basically picks up the search text which is in Vietnamese or Korean text , and try  to fetch the content fragments that contains above search text from backend query its not giving us results though hitting query directly in tools in crx gives result.

From backend logs, characters when printed shows as ???.

We tried printing request.getCharacterEncoding and it gives iso-8859-1 and not utf-8. What can be the cause and why search is not giving results in above case.