you can use shared library and it is best practise
Shared library files in WebSphere Application Server consist of a symbolic name, a Java classpath, and a native path for loading Java Native Interface (JNI) libraries.
You can define a shared library at the application level
A separate class loader is used for shared libraries that are associated with an application server.
IBM recommend to use shared libraries and it is easy to manage and troubleshoot the problem.
example check this link
http://www.ibm.com/developerworks/websphere/library/techarticles/0611_totapally/0611_totapally.html