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ClassNotFoundException when using custom appenders in OSGi projects #72

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simonzn opened this issue Mar 13, 2024 · 0 comments · May be fixed by #73
Open

ClassNotFoundException when using custom appenders in OSGi projects #72

simonzn opened this issue Mar 13, 2024 · 0 comments · May be fixed by #73

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@simonzn
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simonzn commented Mar 13, 2024 •
edited

Due to classpath separation in OSGi based projects, loading of custom Appenders fails with e.g.

log4j:ERROR Could not create an Appender. Reported error follows.
java.lang.ClassNotFoundException: ch.sbb.rcs.common.logging.LazyRollingFileAppender cannot be found by org.apache.log4j_1.2.25
	at org.eclipse.osgi.internal.loader.BundleLoader.generateException(BundleLoader.java:541)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass0(BundleLoader.java:536)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:416)
	at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:168)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:525)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:375)
	at org.apache.log4j.helpers.Loader.loadClass(Loader.java:159)
	at org.apache.log4j.xml.DOMConfigurator.parseAppender(DOMConfigurator.java:240)
	at org.apache.log4j.xml.DOMConfigurator.findAppenderByName(DOMConfigurator.java:174)
	at org.apache.log4j.xml.DOMConfigurator.findAppenderByReference(DOMConfigurator.java:189)
	at org.apache.log4j.xml.DOMConfigurator.parseChildrenOfLoggerElement(DOMConfigurator.java:492)
	at org.apache.log4j.xml.DOMConfigurator.parseCategory(DOMConfigurator.java:415)
	at org.apache.log4j.xml.DOMConfigurator.parse(DOMConfigurator.java:932)
	at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:808)
	at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:721)
	at org.apache.log4j.xml.DOMConfigurator.configure(DOMConfigurator.java:839)
       [...]

The manifest should define a buddy policy to enable buddy class loading, as described in Context Class Loader Enhancements.

I'd suggest to add Eclipse-BuddyPolicy: registered. Then, the issue above is fixed by adding Eclipse-RegisterBuddy: org.apache.log4j to the bundle that provides the custom appender.
simonzn added a commit to simonzn/reload4j that referenced this issue Mar 13, 2024
@simonzn
Enables buddy class loading
f817bbb 
Adds the buddy policy 'registered' to the
manifest so that custom appenders provided
by OSGi bundles can be loaded via buddy
class loading.

The providing bundle must define a
corresponding Eclipse-RegisterBuddy header.

Closes qos-ch#72
@simonzn simonzn linked a pull request Mar 13, 2024 that will close this issue
Open
simonzn added a commit to simonzn/reload4j that referenced this issue Mar 13, 2024
@simonzn
Enables buddy class loading
8a6cf22 
Adds the buddy policy 'registered' to the
manifest so that custom appenders provided
by OSGi bundles can be loaded via buddy
class loading.

The providing bundle must define a
corresponding Eclipse-RegisterBuddy header.

Closes qos-ch#72
simonzn added a commit to simonzn/reload4j that referenced this issue Apr 16, 2024
@simonzn
Enables buddy class loading
176b3fb 
Adds the buddy policy 'registered' to the
manifest so that custom appenders provided
by OSGi bundles can be loaded via buddy
class loading.

The providing bundle must define a
corresponding Eclipse-RegisterBuddy header.

Closes qos-ch#72

Signed-off-by: Simon Zilliken <simon.zilliken@sbb.ch>
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Enables buddy class loading simonzn/reload4j
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