The dbwsclient.jar ; file is not present in the ORACLE_HOME\sqlj\lib\ ,
Recommended version for 11g from
contains dbwsclient.jar built with java version 1.4.2_09-b05 which is not appropriate for DB 11g.
How to obtain dbwsclient.jar built version 22.214.171.124 .
According to: Using UTL_DBWS to Make a Database 11g Callout to a Document Style Web Service (Doc ID 841183.1)
"download.oracle.com/technology/sample_code/tech/java/jsp/dbws-callout-utility-10131.zip" is the suggested version of DBWS callout utility on 11g.
The document also describes installation procedure and test script.