Re: NoClassDefFoundError: com/sun/java/accessibility/util/SwingEventMonitor

Tue, 03 Aug 2010 21:59:30 -0700 

Peter,
This kind of problem is why the ContextClassLoader was introduced. Anytime you have a SPI where the core libs needs to find a (potentially) externally defined concrete implementation, the bootstrap loader can't find it, so the context loader has to be set and used - generally to jump back down to the application class loader. 

Not sure where the fault lies as I don't have this code locally.

David Holmes

Pete Brunet said the following on 08/04/10 14:12:

The failure is on this line of code:
AWTEventMonitor.addFocusListener(this)
which resides in ...\classes\sun\awt\windows\accessibility

AWTEventMonitor is a class in jaccess-1_4.jar which is in lib/ext


However, just before the failing line is executed, a println shows these 
two system properties

java.ext.dir: null

java.class.path: \Program 
Files\Java\jdk1.6.0_20\demo\jfc\SwingSet2\SwingSet2.jar



so that seems to explain why a class in a jar in lib/ext won't be found 
(unless there is some other internal means being used to find jar files).



Since I suspect I'll eventually merge this package into the jdk, to 
continue debugging I extracted the jar into the classes directory.


Pete
===
Pete Brunet wrote:

The class loading info wasn't helpful.  If I run jdb I get the log shown
below.  So far the debug info isn't making sense.  Hopefully it will
tomorrow :-)  If someone can decipher this from the log that would be

helpful. 


Exception occurred: java.lang.NoClassDefFoundError (to be caught at:
com.sun.java.accessibility.util.EventQueueMonitor.addTopLevelWindow(),
line=279 bci=119)"thread=AWT-EventQueue-0",
sun.awt.windows.accessibility.AccessibleContextMirror.<init>(), line=584
bci=766

Also, do I need to change my build in order to use jdb?  One source
indicated I need to use a -g option at compile time.  Perhaps this is
why the jdb threads output doesn't show thread IDs.

Thanks, Pete

=== log of debug session ===
C:\SwingSet2>c:\OpenJDK-b96m\jdk7\build\windows-i586-fastdebug\bin\jdb
SwingSet2

java.util.ServiceConfigurationError: com.sun.jdi.connect.Connector:
Provider sun.jvm.hotspot.jdi.SACoreAttachingConnector not found
java.util.ServiceConfigurationError: com.sun.jdi.connect.Connector:
Provider sun.jvm.hotspot.jdi.SADebugServerAttachingConnector not found
java.util.ServiceConfigurationError: com.sun.jdi.connect.Connector:
Provider sun.jvm.hotspot.jdi.SAPIDAttachingConnector not found
Initializing jdb ...

  

stop at sun.awt.windows.accessibility.AccessibleContextMirror:584

    

Deferring breakpoint
sun.awt.windows.accessibility.AccessibleContextMirror:584.
It will be set after the class is loaded.

  

run

    

run SwingSet2
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable

  
VM Started:


wins.length = 1

Set deferred breakpoint
sun.awt.windows.accessibility.AccessibleContextMirror:584

Breakpoint hit: "thread=AWT-EventQueue-0",
sun.awt.windows.accessibility.AccessibleContextMirror.<init>(), line=584
bci=765

AWT-EventQueue-0[1] catch java.lang.NoClassDefFoundError
Deferring all java.lang.NoClassDefFoundError.
It will be set after the class is loaded.
AWT-EventQueue-0[1] step

  

Set deferred all java.lang.NoClassDefFoundError

    


Exception occurred: java.lang.NoClassDefFoundError (to be caught at:
com.sun.java.accessibility.util.EventQueueMonitor.addTopLevelWindow(),
line=279 bci=119)"thread=AWT-EventQueue-0",
sun.awt.windows.accessibility.AccessibleContextMirror.<init>(), line=584
bci=766

AWT-EventQueue-0[1] threads
Group system:

  (java.lang.ref.Reference$ReferenceHandler)0x122                  
Reference Handler                      cond. waiting
  (java.lang.ref.Finalizer$FinalizerThread)0x121                   
Finalizer                           cond. waiting
  (java.lang.Thread)0x120                                          
Signal Dispatcher                      running
  (java.lang.Thread)0x11f                                          
Attach Listener                        running
  (java.lang.Thread)0x252                                          
Java2D Disposer                        cond. waiting
  (java.lang.Thread)0x59e                                          
TimerQueue                           cond. waiting

Group main:

  (java.lang.Thread)0x255                                          
AWT-Shutdown                           cond. waiting
  (java.lang.Thread)0x256                                          
AWT-Windows                           running

  (com.sun.java.accessibility.util.ComponentEvtDispatchThread)0x26a
EventQueueMonitor-ComponentEvtDispatch cond. waiting

  (java.awt.EventDispatchThread)0x3bc                              
AWT-EventQueue-0                       running
  (SwingSet2$DemoLoadThread)0x691                                  
Thread-1                           running
  (java.lang.Thread)0x692                                          
DestroyJavaVM                          running


=== end log of debug session ===

=== code for addTopLevelWindow ===

    static boolean addTopLevelWindow(Component c) {
        Container parent;

        if (c == null) {
            return false;
        }

        if (!(c instanceof Window)) {
            return addTopLevelWindow(c.getParent());
        }

        if ((c instanceof Dialog) || (c instanceof Window)) {
            parent = (Container) c;
        } else {
            parent = c.getParent();
            if (parent != null) {
                return addTopLevelWindow(parent);
            }
        }

        if (parent == null) {
            parent = (Container) c;
        }

        // Because this method is static, do not make it synchronized
because
        // it can lock the whole class.  Instead, just lock what needs to be
        // locked.
        //
        synchronized (topLevelWindows) {
            if ((parent != null) && !topLevelWindows.contains(parent)) {
                topLevelWindows.addElement(parent);
                if (topLevelWindowListener != null) {

                   
topLevelWindowListener.topLevelWindowCreated((Window) parent);

                }
                return true;
            } else {
                return false;
            }
        }  <----- this is line 279 (if I have the correct source file)
    }

=== end of code for addTopLevelWindow ===

David Holmes wrote:

  

You add it in conjunction with the -XX:+TraceClassLoading.

David

Pete Brunet said the following on 08/03/10 10:15:

    

Hi David, I didn't get any output at all from that one - though it
appears to be a valid parameter as it didn't result in an error
message.  -Pete

David Holmes wrote:

      

Peter,

Try adding -XX:+Verbose to get extra info

David

Pete Brunet said the following on 08/03/10 02:57:

        

Thanks David, Those options tell me which classes were succesfully
loaded but not what classes the class loader was trying to load
when the
class loader was attempting to load SwingEventMonitor.  Is there a way
to get a deeper dump while a particular class is being loaded?  -Pete

David Holmes wrote:

          

Try -verbose:class or -XX:+TraceClassLoading

HTH

David Holmes

Pete Brunet said the following on 07/31/10 07:53:

            

This blog post has been helpful to at least start the investigation:
http://www.jroller.com/sjivan/entry/difference_between_classnotfoundexception_and_noclassdeffounderror




However, I haven't found anything yet similar to the cases
discussed in
the blog entry.  Since SwingEventMonitor was last updated for 1.4
I do
see the use of Class and ListModel instead of Class<T> and
ListModel<T>
but it seems like this would not cause a NoClassDefFoundError.

Other than visual inspection (which I've done) is there a technique
for
determining what classes the class loader is attempting to load as
SwingEventMonitor is being loaded?

Thanks, Pete

Pete Brunet wrote:

              

What is the correct way to fix this?

Exception in thread "AWT-EventQueue-0"
java.lang.NoClassDefFoundError:
com/sun/java/accessibility/util/SwingEventMonitor
        at
sun.awt.windows.accessibility.AccessibleContextMirror.<init>(AccessibleContextMirror.java:583)




This class lives in jaccess-1_4.jar which I copy to lib\ext and is
documented here:
http://download.oracle.com/docs/cd/E17802_01/j2se/javase/technologies/accessibility/docs/jaccess-1.3/doc/api/com/sun/java/accessibility/util/package-summary.html




Since (as far as I know) this class isn't part of the OpenJDK I
expected
javac to fail but it didn't (at least as far as the log shows):

...
# Java sources to be compiled: (listed in file
c:/OPF6CE~1/jdk7/build/WINDOW~2/tmp/sun/sun.awt/awt/.classes.list)
../../../src/windows/classes/sun/awt/windows/Accessibility/AccessibleContextMirror.java



# Running javac:
c:/OPF6CE~1/jdk7/build/WINDOW~2/J2SDK-~1/bin/javac
-J-XX:ThreadStackSize=768 -J-XX:-PrintVMOptions
-J-XX:+UnlockDiagnosticVMOptions -J-XX:-LogVMOutput -J-client
-J-Xmx395m
-J-Xms128m -J-XX:PermSize=32m -J-XX:MaxPermSize=160m -source 7
-target 7
-encoding ascii
-Xbootclasspath:c:/OPF6CE~1/jdk7/build/WINDOW~2/classes
-sourcepath
c:/OPF6CE~1/jdk7/build/WINDOW~2/gensrc;../../../src/windows/classes;../../../src/share/classes



-d c:/OPF6CE~1/jdk7/build/WINDOW~2/classes
@c:/OPF6CE~1/jdk7/build/WINDOW~2/tmp/sun/sun.awt/awt/.classes.list.filtered



/usr/bin/mkdir -p
c:/OPF6CE~1/jdk7/build/WINDOW~2/tmp/sun/sun.awt/awt/obj
...

The source for SwingEventMonitor isn't in any of the three
directories
in the -sourcepath.

What files should I provide and where should I put them, both for
compile time and run time?

Thanks, Pete

  
                























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