Hi, Last week I was testing deploying a war file with RESTEasy on 1.2.1.GA in the war archive's WEB-INF/lib directory and I was getting a CCE like the one below. 12:39:58,448 ERROR [[/infinispan-server-rest]] Exception starting filter Resteasy: java.lang.ClassCastException: org.jboss.resteasy.spi.ResteasyProviderFactory cannot be cast to org.jboss.resteasy.spi.ResteasyProviderFactory at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.init(ServletContainerDispatcher.java:55) [:] at org.jboss.resteasy.plugins.server.servlet.FilterDispatcher.init(FilterDispatcher.java:39) [:] at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:462) [:] at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3286) [:] at org.apache.catalina.core.StandardContext.start(StandardContext.java:3887) [:] AS ships with a different version of RESTEasy library which would explain this issue (latest AS ships 2.0-beta-2). However, AFAIR in the past WEB-INF/lib was deployed under a different classloader and hence this shouldn't be a problem, should it? FilterDispatcher is a class that's only in REST 2.0, so somehow tomcat's ApplicationFilterConfig loads a 2.0 filter class (this is probably configured in some web.xml somewhere) but when this 2.0 class tries to load ResteasyProviderFactory, this is loaded from the war's lib directory (1.x). providerFactory = (ResteasyProviderFactory) servletContext.getAttribute(ResteasyProviderFactory.class.getName()); So, the underlying issue might be related to a change in initialisation or deployment from RESTEasy 1.x to 2.x. Cheers, -- Galder Zamarreño Sr. Software Engineer Infinispan, JBoss Cache