https://www.dotnetzone.gr:443/cs/blogs/birbilis/archive/2013/06/25/fix-java-servletexception-incompatibleclasschangeerror.aspxwas getting an error like the following at your JavaEE Servlet (Portlets are also Servlets under the hood btw): javax.servlet.ServletException: javax.portlet.PortletException: java.lang.Throwable: java.lang.IncompatibleClassChangeError: : incorrect callelCommunityServer 2.1 SP3 (Build: 20423.1)