LinkageError: when resolving interface method “com.hazelcast.core.IMap.getLocalMapStats()"

Vikrant Korde.

We have a springboot project. It generates EAR and same goes in weblogic. Sometimes while starting the application we observe below log in the log file.

Caused by: java.lang.LinkageError: loader constraint violation: when resolving interface method "com.hazelcast.core.IMap.getLocalMapStats()Lcom/hazelcast/monitor/LocalMapStats;" the class loader (instance of <bootloader>) of the current class, java/lang/Object, and the class loader (instance of weblogic/utils/classloaders/ChangeAwareClassLoader) for the method's defining class, com/hazelcast/core/IMap, have different Class objects for the type com/hazelcast/monitor/LocalMapStats used in the signature
at java.lang.invoke.MethodHandleNatives.resolve(Native Method) ~[?:1.8.0_141]
at java.lang.invoke.MemberName$Factory.resolve(MemberName.java:975) ~[?:1.8.0_141]
at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:1000) ~[?:1.8.0_141]
at java.lang.invoke.MethodHandles$Lookup.resolveOrFail(MethodHandles.java:1386) ~[?:1.8.0_141]
at java.lang.invoke.MethodHandles$Lookup.findVirtual(MethodHandles.java:861) ~[?:1.8.0_141]
at io.micrometer.core.instrument.binder.cache.HazelcastIMapAdapter.resolveIMapMethod(HazelcastIMapAdapter.java:202) ~[micrometer-core-1.5.7.jar:1.5.7]
at io.micrometer.core.instrument.binder.cache.HazelcastIMapAdapter.<clinit>(HazelcastIMapAdapter.java:39) ~[micrometer-core-1.5.7.jar:1.5.7]

We are using Hazelcast 3.12.9 and many other dependencies in our project. I do understand that java.lang.LinkageError happens when there are 2 or more versions found for the class. As per above message it seems there are 2 versions of com.hazelcast.monitor.LocalMapStats is getting loaded. The questions that are not answered are

1. How to find the jar which are having 2 versions of com.hazelcast.monitor.LocalMapStats class?
2. Is there any role of loaders and <weblogic/utils/classloaders/ChangeAwareClassLoader> in this error?
3. There is another way to define to give priority to web application jar compared to weblogic jars by specifying prefer-web-inf-classes = false (more details https://docs.oracle.com/cd/E12840_01/wls/docs103/webapp/weblogic_xml.html#wp1067857)

On Oracle support we found an article 1316723.1 which says that we should not use wls:prefer-web-inf-classes in your weblogic.xml. This is an old practice and we should use filtering classloader in weblogic-applicaton.xml.

However problem is still not resolved. It looks like some version incompatibility issue between micrometer-core-1.5.7.jar and com.hazelcast-3.12.9. Micrometer needs Hazlecast with version 4.X. But somehow my project is loading hazelcast 3.12.9.

Please guide on how to get rid of this issue.

Vikrant Korde.

To resolve this error, we removed all the traces of Hazlecast 4.X version. We added excludes for Jar dependencies. We also got rid of Micrometer.

This is not a clean solution but project is working fine now.