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From: Harald Wehr <hwehr@hs-harz.de>
Subject: Re: ClassCastException for Postgres datasource in Generator
Date: Mon, 15 Dec 2003 15:03:50 +0100
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Geoff Howard wrote:
> Harald Wehr wrote:
> 
>> Thanks for your fast answer. I tested your hints but that didn't help. 
>> Nevertheless there is an interesting debug output. If I call 
>> conn.getClass().getName() to the connection I get from the pool, the 
>> output is:
>> ------------
>> $Proxy4
>> ------------
> 
> 
> Looks to me like Excalibur is wrapping the class in a dynamic proxy
> which is then leading to the class cast exception.  Unfortunately, I
> don't know whether you're supposed to find an abstracted api within
> excalibur datasource for the feature you want (which seemed to be
> hinted at by Bertrand's answer, or if "fixing" the proxy is what is 
> needed, or if this is just a good old fashioned bug or unimplemented
> feature.
> 
> I seem to recall that excalibur was using the dynamic proxies in order 
> to get around JDK 1.3/1.4 differences in jdbc.  So, my guess is you are
> using JDK 1.3?  If so, perhaps switching to 1.4 would make the proxy 
> unnecessary and would be a workaround.

I'm already working with JDK 1.4.2, so this can't be an issue here.

> 
> BTW, what does the stack trace say besides ClassCastException?

Here is the full stack trace:

java.lang.ClassCastException
         at 
de.hsharz.vrgis.cocoon.SVGGenerator.getVector(SVGGenerator.java:68)
         at 
de.hsharz.vrgis.cocoon.SVGGenerator.convert(SVGGenerator.java:135)
         at 
de.hsharz.vrgis.cocoon.SVGGenerator.generate(SVGGenerator.java:336)
         at 
org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:549)
         at 
org.apache.cocoon.components.pipeline.impl.AbstractCachingProcessingPipeline.processXMLPipeline(AbstractCachingProcessingPipeline.java:196)
         at 
org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:501)
         at 
org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:147)
         at 
org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:84)
         at 
org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:164)
         at 
org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:108)
         at 
org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:163)
         at 
org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:108)
         at 
org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:152)
         at 
org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:354)
         at 
org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:307)
         at org.apache.cocoon.Cocoon.process(Cocoon.java:656)
         at 
org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:1112)
         at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
         at 
org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:356)
         at 
org.mortbay.jetty.servlet.WebApplicationHandler.dispatch(WebApplicationHandler.java:294)
         at 
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:567)
         at org.mortbay.http.HttpContext.handle(HttpContext.java:1723)
         at 
org.mortbay.jetty.servlet.WebApplicationContext.handle(WebApplicationContext.java:514)
         at org.mortbay.http.HttpContext.handle(HttpContext.java:1673)
         at org.mortbay.http.HttpServer.service(HttpServer.java:879)
         at org.mortbay.http.HttpConnection.service(HttpConnection.java:783)
         at 
org.mortbay.http.HttpConnection.handleNext(HttpConnection.java:945)
         at org.mortbay.http.HttpConnection.handle(HttpConnection.java:800)
         at 
org.mortbay.http.SocketListener.handleConnection(SocketListener.java:201)
         at org.mortbay.util.ThreadedServer.handle(ThreadedServer.java:289)
         at org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:454)


Harald