Re: [JXPath] Lenient getValue() in JXPathContextReferenceImpl

[Bjorn Bength]

Hi again, Dmitri,

I tried the nightly build from tonight (20030124) with the exact same behaviour as before.
I append an extract of the log output at the end of this message,
the xpath expression in this case should be "nod/address/coaddress"
where the bean (nod) in question is in a map in the context.
In this case nod _has_ a property called address and its get-method getAddress(), but that method (or, really, OJBs access methods) inherently throws an (Runtime) exception when it can't materialize the object coz it points to a null in the database.
this nod instance thus have no address and cannot have a coaddress although all access methods are there.


I have some notes about your statements below:
a) To me, if there is a lenient mode, it should quench _all_
errors and exception, but should of course log it properly.
Not just the case where the xpath expression in itself is erreanous.
I should be able to trust the

b) Maybe the lenient mode should be multilevel, one 'quench it all' and
one as you describe it. OR at least describe the actual handling properly in the documentation so that you know you cant trust it.

c) We have a clear use of a superlenient mode, for example in a form on a web page that we can't allow to break just because an object doesnt have an address, and we dont care for what reason it doesnt can't look it up. Maybe we're unique?


Keep up the good work, Dmitri.
and thanks for your time on this.


/Bj�rn




Dmitri Plotnikov wrote:
> Bjorn,
>
> I don't really want to have a catch-all in getValue, even in the
> lenient mode.
>
> When we allowed exceptions during XPath evaluation, the purpose was not
> to conceal all problems, but to ignore <i>irrelevant</i> problems.
>
> Here's my logic:
>
> 1. When you call getValue("/foo/bar"), the implication is: "I know the
> exact path and I want the value that's sitting at the tip of that path.
> If the value is null or some parts of the path are missing, that's ok,
> that's why I switched to the lenient mode. However, if an exception is
> thrown while evaluating the path, something went wrong. I should have a
> way of tracing the problem in order to fix it. This is why I want a
> descriptive exception thrown."
>
> 2. When you call iterate("foo//bar"), the implication is: "I am not
> sure there is anything for foo//bar, but I want to perform the search
> for it and get all matches. As I search for it I will be calling many
> methods that have nothing to do with either foo or bar. I don't care if
> during the search some of those methods, e.g. getBadProperty() or
> getMadAndExplode() throw exceptions, because those properties are
> irrelevant for my search."
>
> This is why in the current cut of JXPath, getValue() throws an
> exception, while iterate() does not.
>
> Does this logic make sense?
>
> - Dmitri
>







The stacktrace.

13391 DEBUG [HttpProcessor[9999][4]] db.NodmodulobjektOpImpl - Query from class se.multicom.prisma.ojb.db.NodmodulobjektImpl where org.apache.
ojb.broker.query.Criteria@45f468
13454 DEBUG [HttpProcessor[9999][4]] db.NodmodulobjektOpImpl - returning: []
[DEFAULT] WARN: OJB broker could not materialize se.multicom.prisma.ojb.db.AddressImpl{0}
[org.apache.ojb.broker.accesslayer.IndirectionHandler] ERROR: Method invoking failed for method *getCoaddress* on object null
null
java.lang.NullPointerException
at org.apache.ojb.broker.accesslayer.IndirectionHandler.invoke(Unknown Source)
at $Proxy0.getCoaddress(Unknown Source)
at java.lang.reflect.Method.invoke(Native Method)
at org.apache.commons.jxpath.util.ValueUtils.getValue(ValueUtils.java:351)
at org.apache.commons.jxpath.ri.model.beans.BeanPropertyPointer.getBaseValue(BeanPropertyPointer.java:151)
at org.apache.commons.jxpath.ri.model.beans.BeanPropertyPointer.getImmediateNode(BeanPropertyPointer.java:177)
at org.apache.commons.jxpath.ri.model.beans.PropertyPointer.getImmediateValuePointer(PropertyPointer.java:171)
at org.apache.commons.jxpath.ri.model.NodePointer.getValuePointer(NodePointer.java:259)
at org.apache.commons.jxpath.ri.JXPathContextReferenceImpl.getValue(JXPathContextReferenceImpl.java:249)
at org.apache.commons.jxpath.ri.JXPathCompiledExpression.getValue(JXPathCompiledExpression.java:101)
at org.apache.cocoon.www.prisma_site.tup.nod.nod_show_xsp.generate(/home/bjorn/tomcat/work/Standalone/localhost/cocoon/cocoon-files/or
g/apache/cocoon/www/prisma_site/tup/nod/nod_show_xsp.java:1135)
at org.apache.cocoon.generation.ServerPagesGenerator.generate(ServerPagesGenerator.java:263)
at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:520)
at org.apache.cocoon.components.pipeline.impl.CachingProcessingPipeline.processXMLPipeline(CachingProcessingPipeline.java:194)
at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:495)
at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:666)
at org.apache.cocoon.components.source.impl.SitemapSource.toSAX(SitemapSource.java:368)
at org.apache.cocoon.environment.AbstractEnvironment.toSAX(AbstractEnvironment.java:454)
at org.apache.cocoon.environment.wrapper.EnvironmentWrapper.toSAX(EnvironmentWrapper.java:319)
at org.apache.cocoon.sitemap.ContentAggregator.generate(ContentAggregator.java:155)
at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.processXMLPipeline(AbstractProcessingPipeline.java:520)
at org.apache.cocoon.components.pipeline.impl.CachingProcessingPipeline.processXMLPipeline(CachingProcessingPipeline.java:194)
at org.apache.cocoon.components.pipeline.AbstractProcessingPipeline.process(AbstractProcessingPipeline.java:495)
at org.apache.cocoon.components.treeprocessor.sitemap.SerializeNode.invoke(SerializeNode.java:142)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:83)
at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:160)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:107)
at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:157)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:107)
at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:152)
at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:327)
at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:309)
at org.apache.cocoon.environment.ForwardRedirector.cocoonRedirect(ForwardRedirector.java:201)
at org.apache.cocoon.environment.ForwardRedirector.redirect(ForwardRedirector.java:113)
at org.apache.cocoon.components.flow.AbstractInterpreter.forwardTo(AbstractInterpreter.java:214)
at org.apache.cocoon.components.flow.javascript.JSCocoon.jsFunction_forwardTo(JSCocoon.java:153)
at inv3.invoke()
at org.mozilla.javascript.FunctionObject.doInvoke(FunctionObject.java:523)
at org.mozilla.javascript.FunctionObject.call(FunctionObject.java:438)
at org.mozilla.javascript.ScriptRuntime.call(ScriptRuntime.java:1244)
at org.mozilla.javascript.continuations.ContinuationInterpreter.interpret(ContinuationInterpreter.java:1561)
at org.mozilla.javascript.continuations.ContinuationInterpreter.interpret(ContinuationInterpreter.java:647)
at org.mozilla.javascript.continuations.ContinuationInterpreter.interpret(ContinuationInterpreter.java:595)
at org.mozilla.javascript.continuations.InterpretedFunctionImpl.call(InterpretedFunctionImpl.java:121)
at org.apache.cocoon.components.flow.javascript.JavaScriptInterpreter.handleContinuation(JavaScriptInterpreter.java:261)
at org.apache.cocoon.components.treeprocessor.sitemap.ContinueNode.invoke(ContinueNode.java:100)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:83)
at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:160)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:107)
at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:157)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:107)
at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:152)
at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:327)
at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:309)
at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:131)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:83)
at org.apache.cocoon.components.treeprocessor.sitemap.PreparableMatchNode.invoke(PreparableMatchNode.java:160)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:107)
at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:157)
at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:107)
at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:152)
at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:327)
at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:309)
at org.apache.cocoon.Cocoon.process(Cocoon.java:585)
at org.apache.cocoon.servlet.CocoonServlet.service(CocoonServlet.java:999)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:260)
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$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2396)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
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.valves.AccessLogValve.invoke(AccessLogValve.java:469)
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.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1040)
at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1151)
at java.lang.Thread.run(Thread.java:479)


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