[UIMA-3692] Classloading inconsistencies

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Not A Problem
• Affects Version/s: 2.0.0uimaFIT
• Component/s: uimaFIT
• Assignee: Richard Eckart de Castilho
• Reporter: Richard Eckart de Castilho
• Created: 23/Mar/14 11:47
• Updated: 01/Aug/18 22:40
• Resolved: 01/Aug/18 22:40

Description

The type discovery mechanism relies on Spring tech and eventually on org.springframework.util.ClassUtils.getDefaultClassLoader() which tries the following classloaders:

• Thread.currentThread().getContextClassLoader()
• ClassUtils.class.getClassLoader()

This allows it to override the classloader used for type scanning by setting the thread classloader.

However, when we actually instantiate components, we rely on UIMA tech which uses:

• getUimaContextAdmin().getResourceManager().getExtensionClassLoader()
• Class.forName(annotatorClassName)

In particular, it does not look at the thread context.

To make classloading consistent, it appears that uimaFIT should check if there is a thread classloader and configure it as the extension classloader for UIMA components created via uimaFIT. Because uimaFIT is using mainly static methods, respecting the thread classloader appears to be the most sensible thing. At least better than setting a global classloader.

To give some context: I hit this problem when running a uimaFIT pipeline from a Jython script. The first problem was to allow uimaFIT to properly scan the JARs in sys.path of the script context, which I did by setting the thread classloader. After that, I tried to run a UIMA component whose class I had defined in the script. UIMA was not able to find the class for this component:

Traceback (most recent call last):
  File "./bad.jpy", line 39, in <module>
    runPipeline(
	at org.apache.uima.analysis_engine.impl.PrimitiveAnalysisEngine_impl.initializeAnalysisComponent(PrimitiveAnalysisEngine_impl.java:209)
	at org.apache.uima.analysis_engine.impl.PrimitiveAnalysisEngine_impl.initialize(PrimitiveAnalysisEngine_impl.java:158)
	at org.apache.uima.impl.AnalysisEngineFactory_impl.produceResource(AnalysisEngineFactory_impl.java:94)
	at org.apache.uima.impl.CompositeResourceFactory_impl.produceResource(CompositeResourceFactory_impl.java:62)
	at org.apache.uima.UIMAFramework.produceResource(UIMAFramework.java:269)
	at org.apache.uima.UIMAFramework.produceAnalysisEngine(UIMAFramework.java:387)
	at org.apache.uima.analysis_engine.asb.impl.ASB_impl.setup(ASB_impl.java:255)
	at org.apache.uima.analysis_engine.impl.AggregateAnalysisEngine_impl.initASB(AggregateAnalysisEngine_impl.java:429)
	at org.apache.uima.analysis_engine.impl.AggregateAnalysisEngine_impl.initializeAggregateAnalysisEngine(AggregateAnalysisEngine_impl.java:373)
	at org.apache.uima.analysis_engine.impl.AggregateAnalysisEngine_impl.initialize(AggregateAnalysisEngine_impl.java:186)
	at org.apache.uima.impl.AnalysisEngineFactory_impl.produceResource(AnalysisEngineFactory_impl.java:94)
	at org.apache.uima.impl.CompositeResourceFactory_impl.produceResource(CompositeResourceFactory_impl.java:62)
	at org.apache.uima.UIMAFramework.produceResource(UIMAFramework.java:269)
	at org.apache.uima.UIMAFramework.produceResource(UIMAFramework.java:314)
	at org.apache.uima.UIMAFramework.produceAnalysisEngine(UIMAFramework.java:425)
	at org.apache.uima.fit.factory.AnalysisEngineFactory.createEngine(AnalysisEngineFactory.java:204)
	at org.apache.uima.fit.pipeline.SimplePipeline.runPipeline(SimplePipeline.java:73)
	at org.apache.uima.fit.pipeline.SimplePipeline.runPipeline(SimplePipeline.java:115)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)

org.apache.uima.resource.ResourceInitializationException: org.apache.uima.resource.ResourceInitializationException: Annotator class "org.python.proxies.__main__$Writer$1" was not found. (Descriptor: <unknown>)