Occured 500 internal server errors

Question

I coding a ap program with jheadstart(version 9.0.5.1.9) and compiler it with
JDeveloper(version 9.0.5.2) then deploy to AS(10.1.2.0.2).
when execution the program sometimes will occured 500 internal server errors
how can i solve this problem?
LOG FILE
java.lang.ClassCastException
at oracle.jheadstart.controller.struts.JhsActionServlet.initModuleMessageResources(JhsActionServlet.java:172)
at org.apache.struts.action.ActionServlet.init(ActionServlet.java:471)
at javax.servlet.GenericServlet.init(GenericServlet.java:258)
at oracle.jheadstart.controller.struts.JhsActionServlet.init(JhsActionServlet.java:219)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.loadServlet(HttpApplication.java:2141)

Answer 1

What you can do, is look up the JHeadstart source code of JhsActionServlet.java line 172. The JHeadstart runtime source code is shipped with your JHeadstart version.
Then, from the source code, try to determine which object can have caused a ClassCastException.
The cause is most likely a Java library (jar) for that type of object that is taken from a different classpath. In other words, the relevant jar might be pre-installed in the OC4J instance, while the class it is cast to is part of your ear file (or the other way around).
Hope this helps,
Sandra Muller
JHeadstart Team
Oracle Consulting