Velocity Initialization failing - apache

Question

I am using velocity as Java Code Generator, I am running a Eclipse application which has multiple plugins and different plugins are calling Velocity module for code generation.
Whenever i run a particular plugin it works fine individually no matter how many times i run it , Now if i will try to run the other plugin it throws velocity exception(i have provided stack trace below), I will restart the eclipse again and other plugin will work fine.
Conclusion: Velocity initialization fails when one plugin runs after some plugin already executed
The code i was using
velocityEngine = new VelocityEngine();
velocityEngine.setProperty(RuntimeConstants.RESOURCE_LOADER, LOCATION);
velocityEngine.setProperty(RESOURCE_LOADER,ClasspathResourceLoader.class.getName());
try {
velocityEngine.init();
} catch (Exception e) {
LOG.error("Failed to load velocity templates e={}", e);
}
i read it is caused by not able to create velocity.log file , then i tried it like this
velocityEngine = new VelocityEngine();
velocityEngine.setProperty(RuntimeConstants.RESOURCE_LOADER, "class,file");
velocityEngine.setProperty(RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS, "org.apache.velocity.runtime.log.Log4JLogChute");
velocityEngine.setProperty("runtime.log.logsystem.log4j.logger", "VELLOGGER");
velocityEngine.setProperty("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
velocityEngine.setProperty("runtime.log.logsystem.class", "org.apache.velocity.runtime.log.NullLogSystem");
/*
velocityEngine.setProperty(RuntimeConstants.RESOURCE_LOADER, LOCATION);
velocityEngine.setProperty(RESOURCE_LOADER,ClasspathResourceLoader.class.getName());
*/
try{
LOG.debug("Velocity Initialisation In AbstractFactory");
velocityEngine.init();
LOG.debug("Velocity Initialisation Done!!!");
}catch(Exception e){
LOG.error("Error Occured In Initialising Velocity Engine {}",e);
}
still it is failing while getting
template = velocityEngine.getTemplate(COMMAND_TEMPLATE_LOCATION.concat(command).concat(TEMPLATE_EXTENSION));
with exception stack trace:
org.apache.velocity.exception.VelocityException: Error initializing log: Failed to initialize an instance of org.apache.velocity.runtime.log.NullLogSystem with the current runtime configuration.
at org.apache.velocity.runtime.RuntimeInstance.initializeLog(RuntimeInstance.java:875)
at org.apache.velocity.runtime.RuntimeInstance.init(RuntimeInstance.java:262)
at org.apache.velocity.app.VelocityEngine.init(VelocityEngine.java:93)
at com.yodlee.dap.cortex.generation.engine.AbstractTemplateFactory.<init>(AbstractTemplateFactory.java:68)
at com.yodlee.dap.cortex.generation.engine.GenericTemplateFactory.<init>(GenericTemplateFactory.java:26)
at com.yodlee.dap.cortex.generation.generator.CodeGenerator.generateCode(CodeGenerator.java:52)
at com.yodlee.dap.cortex.codegenerator.processor.CodeGenProcessor.process(CodeGenProcessor.java:75)
at com.yodlee.dap.cortex.codegenerator.handler.CortexHandler.handle(CortexHandler.java:80)
at com.yodlee.dap.cortex.codegenerator.handler.CortexHandler.handle(CortexHandler.java:48)
at com.yodlee.dap.cortex.codegenerator.generate.CodeGenHandler.generate(CodeGenHandler.java:23)
at com.yodlee.eclipse.json.template.generator.code.TemplateGenerator.writeJavaFile(TemplateGenerator.java:228)
at com.yodlee.eclipse.json.template.generator.code.TemplateGenerator.findNewStates(TemplateGenerator.java:291)
at com.yodlee.eclipse.json.template.generator.code.TemplateGenerator.codeParser(TemplateGenerator.java:137)
at com.yodlee.eclipse.json.site.flow.CodeGenerator.generate(CodeGenerator.java:24)
at com.yodlee.eclipse.json.editor.JsonEditor.addBrowserContent(JsonEditor.java:310)
at com.yodlee.eclipse.json.editor.JsonEditor.setJsonInput(JsonEditor.java:450)
at com.yodlee.eclipse.json.editor.JsonReconcileStrategy$1.run(JsonReconcileStrategy.java:66)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:182)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4211)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3827)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1121)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1022)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:150)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:693)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:610)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:138)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
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)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:673)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:610)
at org.eclipse.equinox.launcher.Main.run(Main.java:1519)
at org.eclipse.equinox.launcher.Main.main(Main.java:1492)
Caused by: org.apache.velocity.exception.VelocityException: Failed to initialize an instance of org.apache.velocity.runtime.log.NullLogSystem with the current runtime configuration.
at org.apache.velocity.runtime.log.LogManager.createLogChute(LogManager.java:220)
at org.apache.velocity.runtime.log.LogManager.updateLog(LogManager.java:269)
at org.apache.velocity.runtime.RuntimeInstance.initializeLog(RuntimeInstance.java:871)
... 42 common frames omitted
Caused by: org.apache.velocity.exception.VelocityException: The specified logger class org.apache.velocity.runtime.log.NullLogSystem does not implement the org.apache.velocity.runtime.log.LogChute interface.
at org.apache.velocity.runtime.log.LogManager.createLogChute(LogManager.java:181)
... 44 common frames omitted
12:32:52.177 [main] DEBUG com.yodlee.dap.cortex.generation.engine.GenericTemplateFactory - Start getGenericTemplate For= GenericClass
12:32:52.180 [main] ERROR com.yodlee.dap.cortex.generation.engine.GenericTemplateFactory - Error Occured In Velocity initialisation Module {}
org.apache.velocity.exception.VelocityException: Error initializing log: Failed to initialize an instance of org.apache.velocity.runtime.log.CommonsLogLogChute with the current runtime configuration.
at org.apache.velocity.runtime.RuntimeInstance.initializeLog(RuntimeInstance.java:875)
at org.apache.velocity.runtime.RuntimeInstance.init(RuntimeInstance.java:262)
at org.apache.velocity.app.VelocityEngine.init(VelocityEngine.java:93)
at com.yodlee.dap.cortex.generation.engine.GenericTemplateFactory.getGenericTemplate(GenericTemplateFactory.java:43)
at com.yodlee.dap.cortex.generation.generator.CodeGenerator.generateCode(CodeGenerator.java:52)
at com.yodlee.dap.cortex.codegenerator.processor.CodeGenProcessor.process(CodeGenProcessor.java:75)
at com.yodlee.dap.cortex.codegenerator.handler.CortexHandler.handle(CortexHandler.java:80)
at com.yodlee.dap.cortex.codegenerator.handler.CortexHandler.handle(CortexHandler.java:48)
at com.yodlee.dap.cortex.codegenerator.generate.CodeGenHandler.generate(CodeGenHandler.java:23)
at com.yodlee.eclipse.json.template.generator.code.TemplateGenerator.writeJavaFile(TemplateGenerator.java:228)
at com.yodlee.eclipse.json.template.generator.code.TemplateGenerator.findNewStates(TemplateGenerator.java:291)
at com.yodlee.eclipse.json.template.generator.code.TemplateGenerator.codeParser(TemplateGenerator.java:137)
at com.yodlee.eclipse.json.site.flow.CodeGenerator.generate(CodeGenerator.java:24)
at com.yodlee.eclipse.json.editor.JsonEditor.addBrowserContent(JsonEditor.java:310)
at com.yodlee.eclipse.json.editor.JsonEditor.setJsonInput(JsonEditor.java:450)
at com.yodlee.eclipse.json.editor.JsonReconcileStrategy$1.run(JsonReconcileStrategy.java:66)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:182)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4211)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3827)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1121)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1022)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:150)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:693)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:610)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:138)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
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)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:673)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:610)
at org.eclipse.equinox.launcher.Main.run(Main.java:1519)
at org.eclipse.equinox.launcher.Main.main(Main.java:1492)
Caused by: org.apache.velocity.exception.VelocityException: Failed to initialize an instance of org.apache.velocity.runtime.log.CommonsLogLogChute with the current runtime configuration.
at org.apache.velocity.runtime.log.LogManager.createLogChute(LogManager.java:220)
at org.apache.velocity.runtime.log.LogManager.updateLog(LogManager.java:269)
at org.apache.velocity.runtime.RuntimeInstance.initializeLog(RuntimeInstance.java:871)
... 41 common frames omitted
Caused by: org.apache.velocity.exception.VelocityException: The specified logger class org.apache.velocity.runtime.log.CommonsLogLogChute does not implement the org.apache.velocity.runtime.log.LogChute interface.
at org.apache.velocity.runtime.log.LogManager.createLogChute(LogManager.java:181)
... 43 common frames omitted

Answer 1

Later i have found the actual root cause of the problem. It was whenever a plugin was initialising the velocity the other plugin was not able to re-initialise it, As the run time environment was same. Additionally both were present as separate module and hence it was not able to access it because of scope issue and hence velocity initialisation was failing.
The solution we implemented as we clubbed both the plugins under single module and hence initialised class from one module was accessible by other.

Answer 2

In my case veolocity and my application was initialized by 2 different class loaders. So when it tries to find the logger class in runtime it cannot find the class. As a solution I had to switched class loaders as a work around(anyway this is not a good way to solve this ).
VelocityEngine ve = new VelocityEngine();
Thread currentThread = Thread.currentThread();
ClassLoader temp = Thread.currentThread().getContextClassLoader();
try
{
currentThread.setContextClassLoader( getClass().getClassLoader() );
ve.setProperty( "runtime.log.logsystem.class", NullLogChute.class.getName() );
ve.init();
}
finally
{
currentThread.setContextClassLoader( temp );
}