[wildfly-dev] Multi-release module JARs

In version 30 of jboss-parent-pom, David Lloyd added the ability to easily produce multi-release jars [1]. While several components consumed by WildFly currently produce multi-release jars (e.g. wildfly-common, Undertow, Infinispan, etc.), as far as I am aware, none of the modules in WildFly (or wf-core) do this. I recently created a pull request to WildFly [2] that ports a collection class from Undertow [3], which, when built using Java 9+, results in faster expiration scheduling for persistent HttpSessions and local @Stateful EJBs. While the changes introduced in this PR are still compatible with JDK 8 [4], this optimization will not be available to users unless they build wildfly using JDK 9+ in order to produce the requisite multi-release jar for the wildfly-clustering-ee-cache module. What do people think about this? Is there any reason why we should *not* compile using JDK 11 when building releases (while still maintaining Java 8 source compatibility, of course)? Even if we continue to create releases using JDK 8 builds, does anyone object to giving users the option to build WildFly with multi-release module jars when compiling with a more recent JDK version? [1] https://issues.redhat.com/browse/WFLY-10178 [2] https://github.com/wildfly/wildfly/pull/13334 [3] https://github.com/undertow-io/undertow/blob/master/core/src/main/java9/i... [4] https://ci.wildfly.org/buildConfiguration/WFPR/207451