Class ClassNotFoundException 加载问题

Question

I have a piece of code which works in one environment and fails with another one. For some reason a class loading fails. I ran the application with a -verbose flag to check for differences but I cannot find the reason. The class causing problems is org.apache.commons.configuration2.PropertiesConfiguration

Other classes from the same library seem to be loaded without issues before.

This is a piece of output where the error occurs:

[52.212s][info][class,load  ] org.apache.commons.beanutils.BeanUtils source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/../../../../../../../git-repositories/knime-scripting/de.mpicbg.knime.scripting.libs/lib/commons-beanutils-1.9.4.jar
[52.213s][info][class,load  ] org.apache.commons.configuration2.io.FileHandler$Updater source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/../../../../../../../git-repositories/knime-scripting/de.mpicbg.knime.scripting.libs/lib/commons-configuration2-2.8.0.jar
[52.213s][info][class,load  ] org.apache.commons.configuration2.io.FileHandler$9 source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/../../../../../../../git-repositories/knime-scripting/de.mpicbg.knime.scripting.libs/lib/commons-configuration2-2.8.0.jar
[52.213s][info][class,load  ] org.apache.commons.configuration2.convert.DefaultListDelimiterHandler source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/../../../../../../../git-repositories/knime-scripting/de.mpicbg.knime.scripting.libs/lib/commons-configuration2-2.8.0.jar
[52.213s][info][class,load  ] org.apache.commons.configuration2.builder.EventListenerProvider source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/../../../../../../../git-repositories/knime-scripting/de.mpicbg.knime.scripting.libs/lib/commons-configuration2-2.8.0.jar
[52.213s][info][class,load  ] org.apache.commons.configuration2.builder.BasicConfigurationBuilder$$Lambda$1498/0x0000000801c16698 source: org.apache.commons.configuration2.builder.BasicConfigurationBuilder
[52.214s][info][class,load  ] org.apache.commons.configuration2.builder.BasicConfigurationBuilder$1 source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/../../../../../../../git-repositories/knime-scripting/de.mpicbg.knime.scripting.libs/lib/commons-configuration2-2.8.0.jar
[52.214s][info][class,load  ] org.apache.commons.lang3.ClassUtils source: file:/Users/niederle/knimeDev/SDK/Eclipse-workspaces/eclipse_2022-07/.metadata/.plugins/org.eclipse.pde.core/.bundle_pool/plugins/org.apache.commons.lang3_3.9.0.jar
FATAL    AWT-EventQueue-0 RGGDialogPanel     org.apache.commons.configuration2.ex.ConfigurationRuntimeException: java.lang.ClassNotFoundException: org.apache.commons.configuration2.PropertiesConfiguration
[52.215s][info][class,load  ] java.lang.Throwable$PrintStreamOrWriter source: jrt:/java.base
[52.215s][info][class,load  ] java.lang.Throwable$WrappedPrintStream source: jrt:/java.base
org.apache.commons.configuration2.ex.ConfigurationRuntimeException: java.lang.ClassNotFoundException: org.apache.commons.configuration2.PropertiesConfiguration
    at org.apache.commons.configuration2.beanutils.BeanHelper.fetchBeanClass(BeanHelper.java:427)
    at org.apache.commons.configuration2.beanutils.BeanHelper.createBeanCreationContext(BeanHelper.java:475)
    at org.apache.commons.configuration2.beanutils.BeanHelper.createBean(BeanHelper.java:353)
    at org.apache.commons.configuration2.beanutils.BeanHelper.createBean(BeanHelper.java:371)
    at org.apache.commons.configuration2.beanutils.BeanHelper.createBean(BeanHelper.java:383)
    at org.apache.commons.configuration2.builder.BasicConfigurationBuilder.createResultInstance(BasicConfigurationBuilder.java:361)
    at org.apache.commons.configuration2.builder.BasicConfigurationBuilder.createResult(BasicConfigurationBuilder.java:338)
    at org.apache.commons.configuration2.builder.BasicConfigurationBuilder.getConfiguration(BasicConfigurationBuilder.java:234)
    at at.ac.arcs.rgg.RGG.initRGG(Unknown Source)

while this is a piece of output where I do not get any error:

[45.850s][info][class,load] org.apache.commons.beanutils.BeanUtils source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-beanutils-1.9.4.jar
[45.919s][info][class,load] org.apache.commons.configuration2.io.FileHandler$Updater source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-configuration2-2.8.0.jar
[45.919s][info][class,load] org.apache.commons.configuration2.io.FileHandler$9 source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-configuration2-2.8.0.jar
[45.948s][info][class,load] org.apache.commons.configuration2.convert.DefaultListDelimiterHandler source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-configuration2-2.8.0.jar
[45.955s][info][class,load] org.apache.commons.configuration2.builder.EventListenerProvider source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-configuration2-2.8.0.jar
[248.267s][info][class,load] org.apache.commons.configuration2.builder.BasicConfigurationBuilder$$Lambda$144/0x0000000800d03740 source: org.apache.commons.configuration2.builder.BasicConfigurationBuilder
[248.280s][info][class,load] org.apache.commons.configuration2.builder.BasicConfigurationBuilder$1 source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-configuration2-2.8.0.jar
[248.313s][info][class,load] org.apache.commons.lang3.ClassUtils source: file:/Users/niederle/knimeDev/git-repositories/rgg/lib/commons-lang3-3.9.jar
[248.316s][info][class,load] java.lang.NumberFormatException source: jrt:/java.base
[248.325s][info][class,load] java.lang.invoke.LambdaForm$DMH/0x0000000800d06000 source: __JVM_LookupDefineClass__
[248.326s][info][class,load] java.lang.invoke.MethodHandle$1 source: jrt:/java.base
[248.335s][info][class,load] java.lang.invoke.LambdaForm$DMH/0x0000000800d06400 source: __JVM_LookupDefineClass__
[248.340s][info][class,load] org.apache.commons.configuration2.PropertiesConfiguration$$Lambda$145/0x0000000800d07000 source: org.apache.commons.configuration2.PropertiesConfiguration
[248.345s][info][class,load] org.apache.commons.configuration2.PropertiesConfiguration$$Lambda$146/0x0000000800d07220 source: org.apache.commons.configuration2.PropertiesConfiguration

I am not sure whether this is the right way to troubleshoot or whether it gives me some hint but I don't see it. I would be happy if anybody could help troubleshooting. Do I need to provide more information? Jars provided should be the same in both environments.

---

EDIT:

I went on with troubleshooting and still don't get the problem.

This is the piece of code causing trouble. While class loading with Class.forName() seems to work, the second part of the code fails with the error mentioned above. In the second part, the class is attempted to be loaded somewhere within builder.getConfiguration() via beanutils .

config = new CompositeConfiguration();
try {
    Class.forName("org.apache.commons.configuration2.PropertiesConfiguration");
} catch (ClassNotFoundException e1) {
    System.out.println("failed to load class");
    e1.printStackTrace();
}
FileBasedConfigurationBuilder<PropertiesConfiguration> builder =
        new FileBasedConfigurationBuilder<PropertiesConfiguration>(PropertiesConfiguration.class)
                    .configure(new Parameters().properties()
                    .setURL(RGG.class.getResource("/at/ac/arcs/rgg/config/elementfactory.properties"))
                    .setThrowExceptionOnMissing(true)
                    .setListDelimiterHandler(new DefaultListDelimiterHandler(';'))
                    .setIncludesAllowed(false));
System.out.println("builder initialized");
PropertiesConfiguration newConfig;
try {
    newConfig = builder.getConfiguration();
    config.addConfiguration(newConfig);
} catch (ConfigurationException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

If this is a library access issue. How would I troubleshoot?

The setup where it fails is the following: The code is part of a jar which is used as a library for an Eclipse plugin (me as author) written for a RCP application (not from me).

Answer 1

Finally, I could solve my issue

I made some mistake here: The full stack trace could have been useful for troubleshooting. Further the setup (not working within an Eclipse plugin) seemed to play an important role.

As far as I understood it, the issue has been caused like this:

RGG.jar (library within my plugin) is dependent on commons-configuration (library in my plugin). But then within commons-configuration a class from the same package has to be loaded with ClassUtils of commons-lang . But commons-lang is provide from outside as Required Plug-ins . It seems that it cannot access this class from outside.

The solution I found was to add commons-lang as a library to that plugin and delete the dependency. Now class loading works.