ClassNotFoundException after enabling a Java Agent on JBoss EAP 6.x and 7.x

Issue

• A ClassNotFoundException occurs during start up of JBoss EAP 6.x in standalone mode after enabling a Java Agent (specifically the Introscope Agent). The standalone.conf was updated to include the Introscope Agent:

# enable Introscope agent
WILY_OPTIONS="-javaagent:/hosting/products/introscope/Agent.jar -Dcom.wily.introscope.agentProfile=/hosting/products/introscope/core/config/bofa/R3.profile -Dcom.wily.introscope.agent.agentName=r3-sit1-01"
JAVA_OPTS="${WILY_OPTIONS} ${JAVA_OPTS}"

The instance couldn't be started. Here is the error from the server.log:

Exception in thread "main" java.lang.NoClassDefFoundError: com/wily/introscope/agent/probe/io/ManagedFileInputStream
        at java.lang.Class.getDeclaredConstructors0(Native Method)
...
Caused by: java.lang.ClassNotFoundException: com.wily.introscope.agent.probe.io.
ManagedFileInputStream from [Module "org.codehaus.woodstox:main" from local modu
le loader @3fd03371 (roots: /var/lib/jboss-eap-6.0/modules)]
        at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:
190)
...