JBoss modules causing LinkageError

Question

java.lang.LinkageError: loader constraint violation: when resolving method "com.sun.mail.util.PropUtil.getBooleanSessionProperty(Ljavax/mail/Session;Ljava/lang/String;Z)Z" the class loader (instance of org/apache/felix/framework/BundleWiringImpl$BundleClassLoader) of the current class, javax/mail/internet/MimeMessage, and the class loader (instance of org/jboss/modules/ModuleClassLoader) for the method's defining class, com/sun/mail/util/PropUtil, have different Class objects for the type javax/mail/Session used in the signature

I have a custom email service that uses the JavaMail API. On a non-JBoss instance, it works fine. On JBoss, it runs into the LinkageError above.

I can't resolve the LinkageError through normal channels, because a critical class is not loading in the usual way:

!! com.sun.mail.util,version=1.5.0 -- Overwritten by Boot Delegation

The JavaMail bundle exports javax.mail and com.sun.mail.util, but the latter is being overwritten by boot delegation and picking up the JBoss module instead, which has its own class loader.

I am not the first to experience this -- see How to debug LinkageError? , Triggering Assets notifications on AEM Forms(JEE) environment -- but I have yet to find an answer for this. It seems that this issue is consistently triggered by using JavaMail (or GatewayMessageService, or any other JavaMail wrapper) on the JBoss turnkey installation.

How can I change the class loader handling to resolve the LinkageError?

kjaeggin · Accepted Answer

I believe you might be referring to a known issue on JEE instances of AEM Forms, which tries to use java mail in OSGi contexts. There are two instances of the javax.mail classes (one provide by AEM, and one provided by Jboss), so sending mail from adaptive forms, etc. will not work due to a class conflict. In order to resolve this you will need to generate a new bundle and replace the existing one. There is a KB article here on how you might resolve this at [1].

[1] Day CQ Mail Service does not work on AEM Forms JEE

adamp25373672 · Answer

I was able to get email working on JBoss by moving javax.mail.*, com.sun.mail.*, and most of javax.activation.* and com.sun.activation.* into our project, completely removing our dependency on the conflicted packages. While far from ideal, this unblocked a critical feature.

I'd still be interested to hear the proper solution for this issue.

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