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Date: Tue, 13 Mar 2012 14:45:34 +0100
From: Thorsten Scherler <scherler@gmail.com>
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To: dev@cocoon.apache.org
Subject: Re: [c3] CallStack.getCurrentFrame() returns null - why?
References: <4F5F3BEB.3000707@gmail.com>
In-Reply-To: <4F5F3BEB.3000707@gmail.com>
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On 03/13/2012 01:22 PM, Thorsten Scherler wrote:
> Hi all,
>
> as I mentioned in another thread I am ATM extracting various code from 
> our main c3 block into separate ones. The extraction works fine for 
> i18n and some general pipes. However we use a activemq queue and when 
> I try to invoke a java pipeline from within a 
> javax.jms.MessageListener I get a NPE in invoking pipe.execute().
>
> I use something like:
>
> ByteArrayOutputStream baos = new ByteArrayOutputStream();
> Pipeline<SAXPipelineComponent> emailPipe = 
> this.applicationContext.getBean("emailPipe", Pipeline.class);
> emailPipe.setup(baos, parameters);
> emailPipe.execute(); -> here we get NPE
>
> I debugged the whole thing and found out that we never enter in the 
> execute() method of the pipeline because before the 
> CallStackCollectorDataStore.set is called.
>
> public void set(String key, Object value) {
>         CallStack.getCurrentFrame().setAttribute(key, value);
>     }
>
> This provokes the following:
> java.lang.NullPointerException
>     at 
> org.apache.cocoon.servlet.collector.CallStackCollectorDataStore.set(CallStackCollectorDataStore.java:28)
>     at 
> org.apache.cocoon.servlet.collector.ResponseHeaderCollector.setModifiedResponse(ResponseHeaderCollector.java:200)
>     at 
> org.apache.cocoon.servlet.collector.ResponseHeaderCollector.interceptInvoke(ResponseHeaderCollector.java:49)
>
> Now finally I found that CallStack.getCurrentFrame() is NULL,  because 
> in CallStack
> public static CallFrame getCurrentFrame() {
>  final Stack stack = (Stack) callStack.get();
> ...
> the stack is null and then the method is returning null provoking this 
> very ugly NPE (which took me ages to track down).
>
> Now my question is how can it be that the stack is null and how can I 
> prevent it from happening? Further I would strongly vote to refactor 
> CallStack.getCurrentFrame().setAttribute to something like
> CallFrame frame = CallStack.getCurrentFrame();
> if(null!=frame){
>   frame.setAttribute(key, value);
> }else{
>   // should we throw here an exception or is there an alternative?
> }
>
> Any ideas are welcome.

Ok, getting closer to the underlying problem. I did
ServletContext xXx = CallStackHelper.getCurrentServletContext();
and surprise surprise "xXx = null"

...now how can I attach the context to my jms listener again?

salu2

-- 
Thorsten Scherler<scherler.at.gmail.com>
codeBusters S.L. - web based systems
<consulting, training and solutions>

http://www.codebusters.es/


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    On 03/13/2012 01:22 PM, Thorsten Scherler wrote:
    <blockquote cite="mid:4F5F3BEB.3000707@gmail.com" type="cite">
      <meta http-equiv="content-type" content="text/html;
        charset=ISO-8859-1">
      Hi all,<br>
      <br>
      as I mentioned in another thread I am ATM extracting various code
      from our main c3 block into separate ones. The extraction works
      fine for i18n and some general pipes. However we use a activemq
      queue and when I try to invoke a java pipeline from within a
      <meta http-equiv="content-type" content="text/html;
        charset=ISO-8859-1">
      javax.jms.MessageListener I get a NPE in invoking pipe.execute().<br>
      <br>
      I use something like:<br>
      <br>
      ByteArrayOutputStream baos = new ByteArrayOutputStream();<br>
      Pipeline&lt;SAXPipelineComponent&gt; emailPipe =
      this.applicationContext.getBean("emailPipe", Pipeline.class);<br>
      emailPipe.setup(baos, parameters);<br>
      emailPipe.execute(); -&gt; here we get NPE<br>
      <br>
      I debugged the whole thing and found out that we never enter in
      the execute() method of the pipeline because before the
      CallStackCollectorDataStore.set is called.<br>
      <br>
      public void set(String key, Object value) {<br>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CallStack.getCurrentFrame().setAttribute(key, value);<br>
      &nbsp;&nbsp;&nbsp; }<br>
      <br>
      This provokes the following:<br>
      java.lang.NullPointerException<br>
      &nbsp;&nbsp;&nbsp; at
org.apache.cocoon.servlet.collector.CallStackCollectorDataStore.set(CallStackCollectorDataStore.java:28)<br>
      &nbsp;&nbsp;&nbsp; at
org.apache.cocoon.servlet.collector.ResponseHeaderCollector.setModifiedResponse(ResponseHeaderCollector.java:200)<br>
      &nbsp;&nbsp;&nbsp; at
org.apache.cocoon.servlet.collector.ResponseHeaderCollector.interceptInvoke(ResponseHeaderCollector.java:49)<br>
      <br>
      Now finally I found that CallStack.getCurrentFrame() is NULL,&nbsp;
      because in CallStack <br>
      public static CallFrame getCurrentFrame() {<br>
      &nbsp;final Stack stack = (Stack) callStack.get();<br>
      ...<br>
      the stack is null and then the method is returning null provoking
      this very ugly NPE (which took me ages to track down).<br>
      <br>
      Now my question is how can it be that the stack is null and how
      can I prevent it from happening? Further I would strongly vote to
      refactor CallStack.getCurrentFrame().setAttribute to something
      like <br>
      CallFrame frame = CallStack.getCurrentFrame();<br>
      if(null!=frame){<br>
      &nbsp; frame.setAttribute(key, value);<br>
      }else{<br>
      &nbsp; // should we throw here an exception or is there an alternative?<br>
      }<br>
      <br>
      Any ideas are welcome.<br>
    </blockquote>
    <br>
    Ok, getting closer to the underlying problem. I did<br>
    ServletContext xXx = CallStackHelper.getCurrentServletContext();<br>
    and surprise surprise "xXx = null"<br>
    <br>
    ...now how can I attach the context to my jms listener again?<br>
    <br>
    salu2<br>
    <pre class="moz-signature" cols="72">-- 
Thorsten Scherler &lt;scherler.at.gmail.com&gt;
codeBusters S.L. - web based systems
&lt;consulting, training and solutions&gt;

<a class="moz-txt-link-freetext" href="http://www.codebusters.es/">http://www.codebusters.es/</a>
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