EJB call to varargs method failing from Java7 client - ejb-3.0

Question

We have stateless session bean (EJB 3.0) that has a method which accepts varargs(variable arguments) as inputs. Method signature is as below:-
public String operation1(String arg1,List...arg4);
This EJB is deployed on Weblogic 10.3.2 running on a "Java6" JRE.
When this EJB method is invoked from a Java6 standalone client, the call is successful.
When I change the JRE from Java6 to Java7(without changing any other client code),the call fails with an unmarshal exception(Stack trace below).
javax.ejb.EJBException: Could not unmarshal method ID; nested exception is:
java.rmi.UnmarshalException: Method not found: 'operation1(Ljava.lang.String;Ljava.util.List...;)'; nested exception is: java.rmi.UnmarshalException: Method not found: 'operation1(Ljava.lang.String;Ljava.util.List...;)'
at weblogic.ejb.container.internal.RemoteBusinessIntfProxy.unwrapRemoteException(RemoteBusinessIntfProxy.java:109)
at weblogic.ejb.container.internal.RemoteBusinessIntfProxy.invoke(RemoteBusinessIntfProxy.java:91)
at com.sun.proxy.$Proxy5.operation1(Unknown Source)
at com.MyEJBStandaloneClient.testOperation1(MyEJBStandaloneClient.java:78)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
EJB Code
#Stateless(mappedName = "MyBean")
public class MyBean implements MyBeanRemote{
public String operation1(String arg1,List...arg4) {
System.out.println("Input1 is:-"+arg1);
return "newString";
}
}
Remote class
#Remote
public interface MyBeanRemote {
public String operation1(String arg1,List... arg4);
}
The non-varargs methods(if any are added), within the same EJB are invoked successfully from Java7 clients & it is only the varargs methods in the EJB that have this problem.
Note that the same call works fine even with Java7 if the method signature on the Remote interface class is changed to the following
public String operation1(String arg1,List[] arg4);
But is there any way to make it work without changing the method signature?
Are there any known issues around this?
Thanks.

Answer 1

The problem you described is the consequence of an old bug from WebLogic.
In fact, EJB methods using varargs are ignored when it generates its stub classes.
The deep reason is that WebLogic EJB compiler incorrectly tries to append a transient modifier to the varargs argument.
Obviously, it results in an error, and so, the method stub is not generated.
At that time BEA created a path, CR327275, for WebLogic 10.0.MP1 to correct the issue. Unfortunately, this patch was apparently NOT included in WebLogic 10.3 release...
Feedbacks on this point are not that easy to find, but the Seam community made some. Here they are:
http://in.relation.to/Bloggers/Weblogic10SeamAndEJB3#H-Option1ApplyTheTtCR327275ttPatchBut
https://docs.jboss.org/seam/2.1.2/reference/en-US/html/weblogic.html
So, to solve your issue:
either, as you guessed, you have to change the method signature
or you contact WebLogic to get and install the former patch.
Regards,
Thomas