java.lang.UnsupportedClassVersionError: JVMCFRE003 bad major version; class=okhttp3/MediaType, offset=6 This is the exception I am getting when running the code on WAS 7. I think the okhttp code was compiled using Java 7 or some higher version and when I am trying to use it on WAS 7 which uses java 6. I am using the latest jar (v 3.2) from http://square.github.io/okhttp/