How to find out which jar file is loading the class I am looking for ??

In SOA add the following java code to BPEL Java embeding activity 

++++
System.out.println("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
        try {


System.out.println(Class.forName("oracle.tip.adapter.ftp.SFTPClient").getProtectionDomain().getCodeSource().getLocation());

        }
        catch(Exception e1)
        {
         e1.printStackTrace();
        }

System.out.println("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ");

+++

Result :

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
file:/apps/erikad1/aerikad1/app_ECTH/ecthd0runtime/SOA/domain/ECTH_SOA_Domain/servers/ECTH_SOA1/stage/FtpAdapter1/FtpAdapter.rar

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

You can also add the flag 

export JAVA_OPTIONS="-verbose:class". This writes all the class loading

information to the standard out file.

This displays messages like

[Loaded oracle.tip.adapter.ftp.SFTPAgent from
file:/apps/erikad1/aerikad1/app_ECTH/ecthd0runtime/SOA/domain/ECTH_SOA_Domain/servers/ECTH_SOA1/stage/FtpAdapter1/FtpAdapter.rar]
[Loaded oracle.tip.adapter.ftp.SFTPClient from
file:/apps/erikad1/aerikad1/app_ECTH/ecthd0runtime/SOA/domain/ECTH_SOA_Domain/servers/ECTH_SOA1/stage/FtpAdapter1/FtpAdapter.rar]
[Loaded oracle.tip.adapter.file.outbound.FileLister from

file:/apps/erikad1/aerikad1/app_ECTH/ecthd0soa/fmw/SOA/soa/connectors/FileAdapter.rar]