Re: [Webmacro-devel] Why can't webmacro.jar be replaced without restart?

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Hi,

On Wednesday 23 July 2003 12:11, Marc Palmer wrote:
> Guys, I imagine a few of use are familiar with this message after trying to
> replace webmacro.jar and restarting/reloading the web application without
> restarting the servlet container:
>
> WebMacro Error:
>
> Could not initialize the broker!
> *** Check that WebMacro.properties was in your servlet
> *** classpath, in a similar place to webmacro.jar *** and that all values
> were set correctly.
> IO Error reading WebMacro.defaults
> java.io.FileNotFoundException: JAR entry WebMacro.defaults not found in
> E:\Program Files\Apache Group\Tomcat 4.1\webapps\ignition\WEB-
> INF\lib\webmacro.jar
> Please contact the server administrator
>
>
> Do we know why this is happening? It is hard to see how it can be a WM
> thing, as it looks more like a generic classloader issue.

I've tried to track this down the last two hours, but I have no clue. I did 
the following to get a minimal test case.

I modified Standalone.java from our examples slightly, so that it worked as 
expected:
- Passed a "this" reference in new WM()
- called super.init(sc) at the beginning of the overriden init method

I then created a simple web-app with the following files:
webapps/test/standalone.wm
webapps/WEB-INF/web.xml
webapps/WEB-INF/classes/Standalone.class
webapps/WEB-INF/lib/webmacro.jar

This works as expected. When I "touch" webmacro.jar the webapp gets reloaded 
and everything works as expected. However, when I change a core WebMacro 
class sligthly, so that the size of webmacro.jar changes and put this 
modified webmacro.jar in place, things fails after reloading the webapp.

However, I'm getting another message than Marc which really hints at a 
classloader issue:

avax.servlet.ServletException: Error instantiating servlet class Standalone
        at 
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:912)
        at 
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:668)
        at 
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
        at 
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
        at 
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
        at 
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
        at 
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
        at 
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
        at java.lang.Thread.run(Thread.java:484)
----- Root Cause -----
java.lang.NoClassDefFoundError: org/webmacro/ContextException
        at java.lang.Class.newInstance0(Native Method)
        at java.lang.Class.newInstance(Class.java:237)
        at 
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:903)
        at 
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:668)
        at 
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
        at 
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
        at 
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
        at 
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
        at 
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
        at 
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
        at java.lang.Thread.run(Thread.java:484)

Notice the root cause: 
"java.lang.NoClassDefFoundError: org/webmacro/ContextException"

Needless to say, that I did not do anything to ContextException.

I have no idea what's going on here, or how to track this down.

This all happens under tomcat-4.1.24

Sebastian

-- 
Sebastian Kanthak
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