Storing a LinkedHashMap subclass in the session breaks replication. ------------------------------------------------------------------- Key: WFLY-9541 URL: https://issues.jboss.org/browse/WFLY-9541 Project: WildFly Issue Type: Bug Components: Clustering Affects Versions: 12.0.0.Alpha1 Environment: Tested on JDK 1.8.0_152 on OS X 10.12 Reporter: Klaasjan Brand Assignee: Paul Ferraro Context: trying to get one of our applications to work with Wildfly session replication. After trying out a build from the Wildfly master branch to test another bug I submitted I noticed another issue which works fine in the Wildfly 11 release. Our application has a custom LinkedHashMap subclass (MostRecentlyUsedMap from the Wicket framework) which it stores in the session. It also keeps a reference to the subclass since that one has a few extra fields. When marshalling the session the MostRecentlyUsedMap is converted to a LinkedHashMap. When unmarshalling the session this causes an error since the field is of the subclass type. This behaviour is new in WF 12 and is related to this commit: https://github.com/wildfly/wildfly/commit/143527f595206c5f2bf037b47c797f0... (fix for the WFLY-9497 issue).