Re: gcj & JMX

[Andrew John Hughes <gnu_andrew at member dot fsf dot org>]

On Wed, 2007-02-14 at 18:14 +0000, Andrew Haley wrote:
> I've come across a bug (or just a difference) between mx4j and
> Classpath that prevents Tomcat's org.apache.catalina.core.StandardHost
> from being initialized correctly.
> 
> 
> org.apache.commons.modeler.Registry.registerComponent() 
> 
> calls 
> 
> getMBeanServer().registerMBean( mbean, oname)
> 
> with oname = javax.management.ObjectName@2aaab4e37e00
> {
>   java.lang.String canonicalName = "Catalina:host=localhost,type=Host",
>   java.lang.String propertiesString = "type=Host,host=localhost",
>   boolean isDomainPattern = false,
>   boolean isPropertyPattern = false,
> }
> 
> 
> with mx4j, the calling sequence is then
> 
> mx4j.server.MX4JMBeanServer.registerMBean(java.lang.Object, javax.management.ObjectName)javax.management.ObjectInstance
>    at mx4j/server/MX4JMBeanServer.java:753
> 
> mx4j.server.MX4JMBeanServer.registerMBeanImpl(java.lang.Object, javax.management.ObjectName, boolean)javax.management.ObjectInstance
>    at mx4j/server/MX4JMBeanServer.java:769
> 
> mx4j.server.MX4JMBeanServer.registerImpl(mx4j.server.MBeanMetaData, boolean)void
>     at mx4j/server/MX4JMBeanServer.java:822
> 
> mx4j.server.interceptor.ContextClassLoaderMBeanServerInterceptor.registration(mx4j.server.MBeanMetaData, int)void
>     at mx4j/server/interceptor/ContextClassLoaderMBeanServerInterceptor.java:159
> 
> mx4j.server.interceptor.DefaultMBeanServerInterceptor.registration(mx4j.server.MBeanMetaData, int)void
>     at mx4j/server/interceptor/DefaultMBeanServerInterceptor.java:110
> 
> mx4j.server.interceptor.DefaultMBeanServerInterceptor.registration(mx4j.server.MBeanMetaData, int)void
>     at mx4j/server/interceptor/DefaultMBeanServerInterceptor.java:110
> 
> mx4j.server.interceptor.SecurityMBeanServerInterceptor.registration(mx4j.server.MBeanMetaData, int)void
>     at mx4j/server/interceptor/SecurityMBeanServerInterceptor.java:133
> 
> mx4j.server.interceptor.DefaultMBeanServerInterceptor.registration(mx4j.server.MBeanMetaData, int)void
>     at mx4j/server/interceptor/DefaultMBeanServerInterceptor.java:110
> 
> mx4j.server.interceptor.InvokerMBeanServerInterceptor.registration(mx4j.server.MBeanMetaData, int)void
>     at mx4j/server/interceptor/InvokerMBeanServerInterceptor.java:157
> 
> org.apache.commons.modeler.BaseModelMBean.preRegister(javax.management.MBeanServer, javax.management.ObjectName)javax.management.ObjectName 
>     at org/apache/commons/modeler/BaseModelMBean.java:1397
> 
> org.apache.catalina.core.StandardHost.preRegister(javax.management.MBeanServer, javax.management.ObjectName)javax.management.ObjectName
>     at org/apache/catalina/core/StandardHost.java:807
> 
> org.apache.catalina.core.ContainerBase.preRegister(javax.management.MBeanServer, javax.management.ObjectName)javax.management.ObjectName
>     at org/apache/catalina/core/ContainerBase.java:1406
> 
> 
> With Classpath, none of this ever happens.  Instead,
> gnu.javax.management.registerMBean(Object, ObjectName) does not call
> MBeanRegistration.preRegister() unless ObjectName == null.
> 
> So, the preRegister method is never called.
> 
> The spec for MBeanServer.registerMBean() says "If the object name
> given is null, the MBean must provide its own name by implementing the
> MBeanRegistration interface and returning the name from the
> preRegister method."
> 
> I suspect, however, that if the MBean is implements the
> MBeanRegistration interface we should call the preRegister method
> regardless.
> 
> I'm going to try it.
> 
> Andrew.

Sounds good to me; I hope this fixes the problem.  Maybe I shouldn't
stick to the specs and just go with common sense in future... ;)

Thanks for spotting this,
Cheers,
-- 
Andrew :-)

Escape the Java Trap with GNU Classpath!
http://www.gnu.org/philosophy/java-trap.html
public class gcj extends Freedom implements Java { ... }

Attachment: signature.asc
Description: This is a digitally signed message part