Hello,
I'm working in a project where we use felix/osgi to create a
"plugin-framework" for a client side application. It works very well but we
sometimes run into class loading problems, especially when one of our
"plugin"-bundles use third part libraries that loads classes through
Class.forName().
Short description of the system:
Our system consists of our main application (not loaded through osgi) that
"embeds" Felix and starts the system bundle. We then use FileInstall to add
plugins (ie other bundles).
Problem:
SwingX is one of the libraries that use Class.forName() and
Class.getClassLoader().loadClass(). It does this to support different lafs
(such as Substance) and the calls are in a class named LookAndFeelAddons.
Here, it asks the UIManager to get the UI-class for a certain
SwingX-component and then load the UI-class using either forName() or
getClassLoader().loadClass(). So, if a class in a plugin is using a SwingX
component, that bundle/plugin must have access to the UI-class. This causes
problems. We have one plugin with a JPanel-class that uses the JXHeader from
the SwingX library. When the component is created we get the following
ClassNotFoundException:
java.lang.RuntimeException: java.lang.RuntimeException: Failed to load class
org.jvnet.substance.swingx.SubstanceHeaderUI
at
consilium.publish.wizard.ProfilesPanel$EditProfileWorker.done(ProfilesPanel.java:473)
at javax.swing.SwingWorker$5.run(SwingWorker.java:718)
at
javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:864)
at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:95)
at
javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:874)
at javax.swing.Timer.fireActionPerformed(Timer.java:271)
at javax.swing.Timer$DoPostEvent.run(Timer.java:201)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at
consilium.tools.InputZookeeper.dispatchEvent(InputZookeeper.java:709)
at
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
at java.awt.Dialog$1.run(Dialog.java:1051)
at java.awt.Dialog$3.run(Dialog.java:1103)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Dialog.java:1101)
at java.awt.Component.show(Component.java:1516)
at java.awt.Component.setVisible(Component.java:1468)
at java.awt.Window.setVisible(Window.java:841)
at java.awt.Dialog.setVisible(Dialog.java:991)
at consilium.gui.SizedDialog.setVisible(SizedDialog.java:136)
at consilium.actions.MenuBuilder$16$1$1.run(MenuBuilder.java:490)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at
consilium.tools.InputZookeeper.dispatchEvent(InputZookeeper.java:709)
at
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Caused by: java.lang.RuntimeException: Failed to load class
org.jvnet.substance.swingx.SubstanceHeaderUI
at
org.jdesktop.swingx.plaf.LookAndFeelAddons.getUI(LookAndFeelAddons.java:319)
at org.jdesktop.swingx.JXHeader.updateUI(JXHeader.java:181)
at javax.swing.JPanel.<init>(JPanel.java:69)
at javax.swing.JPanel.<init>(JPanel.java:92)
at javax.swing.JPanel.<init>(JPanel.java:100)
at org.jdesktop.swingx.JXPanel.<init>(JXPanel.java:110)
at org.jdesktop.swingx.JXHeader.<init>(JXHeader.java:113)
at
se.conciliate.htmlprofileeditor.editor.HTMLProfileEditor.initComponents(HTMLProfileEditor.java:353)
at
se.conciliate.htmlprofileeditor.editor.HTMLProfileEditor.init(HTMLProfileEditor.java:98)
at
se.conciliate.htmlprofileeditor.editor.HTMLProfileEditor.<init>(HTMLProfileEditor.java:86)
at
se.conciliate.htmlprofileeditor.HTMLPublishProfileService.editProfile(HTMLPublishProfileService.java:124)
at
consilium.publish.wizard.ProfilesPanel$EditProfileWorker.done(ProfilesPanel.java:465)
... 31 more
Caused by: java.lang.ClassNotFoundException:
org.jvnet.substance.swingx.SubstanceHeaderUI
at
org.apache.felix.framework.searchpolicy.R4SearchPolicyCore.findClass(R4SearchPolicyCore.java:198)
at
org.apache.felix.framework.searchpolicy.R4SearchPolicy.findClass(R4SearchPolicy.java:45)
at
org.apache.felix.framework.searchpolicy.ContentClassLoader.loadClass(ContentClassLoader.java:118)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at
org.jdesktop.swingx.plaf.LookAndFeelAddons.getUI(LookAndFeelAddons.java:316)
... 42 more
Caused by: java.lang.ClassNotFoundException:
org.jvnet.substance.swingx.SubstanceHeaderUI
at
org.apache.felix.framework.searchpolicy.R4SearchPolicyCore.findClassOrResource(R4SearchPolicyCore.java:486)
at
org.apache.felix.framework.searchpolicy.R4SearchPolicyCore.findClass(R4SearchPolicyCore.java:185)
... 46 more
As you can see, LookAndFeelAddons wraps the exception in a RuntimeException.
But it is clear from the Caused by that it is indeed a
ClassNotFoundException and that the class that cannot be found is
org.jvnet.substance.swingx.SubstanceHeaderUI. This class is part of the main
application and thus not loaded (exported) to the OSGi-framework. The
offending class is the UI-class for the SwingX component JXHeader under the
Substance look and feel. Now, I'm no master at class loading and certainly
not at OSGi class loading. But as I understand it, the bundle/plugin gets
its own class loader. Is there any way to set things up so that the
bundle/plugin class loader can delegate the class loading to the main
applications class loader. I mean, since the main application has
org.jvnet.substance.swingx.SubstanceHeaderUI on its classpath it will be
able to load it (and is able to load it in all code that we use from the
main application).
Hope I have explained the problem decently enough. I first thought about
exporting the package org.jvnet.substance.swingx from the system bundle and
importing it from the plugin-bundle. But this is not desirable since the
plugin shouldn't be tied to our specific LAF (it shouldn't even have to know
that we use Substance and it shouldn't have to know the internal workings of
swingx-laf addons).
Regards,
Per-Erik Svensson
