Created attachment 889034 [details]
Reproducer

Description of problem:
The Seam 2.2 Drools module fails in EAP 6.3 on JDK8 with the following exception:
...
Caused by: java.lang.RuntimeException: wrong class format
	at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:260) [drools-compiler.jar:5.1.0.BRMS-jdk7]
	at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:204) [drools-compiler.jar:5.1.0.BRMS-jdk7]
...
Caused by: org.eclipse.jdt.internal.compiler.classfmt.ClassFormatException
	at org.eclipse.jdt.internal.compiler.classfmt.ClassFileReader.<init>(ClassFileReader.java:372) [ecj-4.3.1.redhat-1.jar:4.3.1.redhat-1]
	at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:254) [drools-compiler.jar:5.1.0.BRMS-jdk7]

Version-Release number of selected component (if applicable):
EAP 6.3.0.ER2 (target)
EAP 5.3.0.ER3 (Seam)

Steps to reproduce:
1. Deploy the EAP6-migrated Seam 2.2 Drools example to EAP 6.3 running on JDK8.
2. Open http://localhost:8080/seam-drools
3. Submit any valid number

Actual results:
HTTP 500 Error appears, with the above mentioned exception.

Expected results:
The application works.