Fwd: MBeanOperationInfo array return types

Just found part of the answer in the jmx spec under MBeanOperationInfo Class...

To para-phrase, getReturnType must return a string that's identical to the 
string returned by the getName method of java.lang.Class.  So 
Commons-Modeler has the bug, and MX4J is solid.

[Ljava.lang.Object; looks a little odd in the HttpAdaptor though...

Thanks,
Kirk

>Date: Tue, 17 Aug 2004 11:18:08 -0700
>To: [email protected]
>From: Kirk Lund <[email protected]>
>Subject: MBeanOperationInfo array return types
>
>We are using Jakarta Commons-Modeler in combination with MX4J.  By default 
>Commons-Modeler uses it's own impl of ModelMBean, but we are using the 
>MX4J impl of RequiredModelMBean.  This has highlighted a couple bugs in 
>Commons-Modeler.  However, one of the bugs could feasibly be considered an 
>MX4J bug.
>
>If Modeler configures a ModelMBean to have an operation which returns an 
>array of javax.management.ObjectName[] (or any object array...), it 
>produces the following situation...
>
>1) Modeler takes the String "javax.management.ObjectName[]" and simply 
>sets the MBeanOperationInfo return type to that string instead of 
>"[Ljavax.management.ObjectName;"
>
>2) MX4J's RequiredModelMBean enters method "invoke" and hits the following 
>line with "javax.management.ObjectName[]"...
>     Class declared = 
> loadClassWithContextClassLoader(operInfo.getReturnType());
>...loadClassWithContextClassLoader returns null.  RequiredModelMBean then 
>calls method "checkAssignability" which throws a NullPointerException 
>because variable "declared" is always assumed to never be null throughout.
>
>So, my main question is... should MX4J be altered to cope with 
>non-reflective array strings (ie, "java.lang.Object[]")?
>
>It would be inappropriate to set the Modeler descriptor xml file to have 
>"[Ljavax.management.ObjectName;" as the return type.  Why?  Because the 
>descriptor xml file should remain human readable and "Object[]" format is 
>appropriate in the xml.  One alternative to altering MX4J is to alter 
>Modeler to convert the string to the "[L..." format after reading in the 
>xml.  However, it's not clear from reading the JMX spec or the JavaDocs on 
>MBeanOperationInfo that the return type shouldn't display the "Object[]" 
>format as a return from MBeanOperationInfo.getReturnType().
>
>Another alternative would be to change ModelMBeanOperationInfo or 
>MBeanOperationInfo to convert the type string from "Object[]" to the 
>reflective "[L...".
>
>I would be happy to tackle a solution in either direction and provide the 
>necessary patch.  At the very least I believe RequiredModelMBean should be 
>altered to check for null "declared" instead of blowing up with a 
>NullPointerException.
>
>You're all more familiar w/ the spec and MX4J than I...  What you 
>think?  Which solution is more appropriate in your opinions?
>
>Thanks,
>Kirk
>
>PS: In addition to the NPE, I also get the expected ClassNotFoundException...
>java.lang.ClassNotFoundException: javax.management.ObjectName[]
>         at java.net.URLClassLoader$1.run(URLClassLoader.java:199)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
>         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
>         at mx4j.util.Utils.loadClass(Utils.java:99)
>         at 
> javax.management.modelmbean.RequiredModelMBean.loadClassWithContextClassLoader(RequiredModelMBean.java:1194)
>         at 
> javax.management.modelmbean.RequiredModelMBean.invoke(RequiredModelMBean.java:669)
>         at 
> mx4j.server.interceptor.InvokerMBeanServerInterceptor.invoke(InvokerMBeanServerInterceptor.java:218)
>         at 
> mx4j.server.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:121)
>         at 
> mx4j.server.interceptor.SecurityMBeanServerInterceptor.invoke(SecurityMBeanServerInterceptor.java:86)
>         at 
> mx4j.server.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:121)
>         at 
> mx4j.server.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:121)
>         at 
> mx4j.server.interceptor.ContextClassLoaderMBeanServerInterceptor.invoke(ContextClassLoaderMBeanServerInterceptor.java:205)
>         at mx4j.server.MX4JMBeanServer.invoke(MX4JMBeanServer.java:1079)
>         at 
> mx4j.tools.adaptor.http.InvokeOperationCommandProcessor.executeRequest(InvokeOperationCommandProcessor.java:164)
>         at 
> mx4j.tools.adaptor.http.HttpAdaptor$HttpClient.run(HttpAdaptor.java:980)




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