Problem with XPL/DelegationProcessor (EJB)

Hi,

I call EJB methods from my form (e.g. to save specific data using existing
methods from a separate application). When I call e.g. a String method the
text-serializer does his job, but I haven't figured out how to call a void
method (or to ignore the return value).

If I remove the p:output from the delegation processor, i get an error which
tells me that the output element is missing. When it's there i get a
NullPointerException like this one:

ERROR ProcessorService - Exception at oxf:/apps/services/new-message.xpl
(executing XSLT transformation)
java.lang.NullPointerException
        at
org.orbeon.oxf.processor.DelegationProcessor.callMethod(DelegationProcessor.java:469)
        at
org.orbeon.oxf.processor.DelegationProcessor.access$200(DelegationProcessor.java:55)
        at
org.orbeon.oxf.processor.DelegationProcessor$2.endElement(DelegationProcessor.java:381)

I use XSLT to get values from the submittet instance and use them as arguments
for the EJB method (I don't know if that's the proper way to do this, but I
found no other solution). Without XSLT (and static values) the error is the
same but starts with:

ERROR ProcessorService - Exception at line x, column y of
oxf:/apps/services/tm-newtask.xpl (reading processor output: name='data',
id='ejb-data')

(where x/y points to the end of the delegation-processor output)


When i call a 'non-void' method whose return value is not of interest to me (i
want to ignore it by removing the text-serializer) the method is not called,
nothing happens which leads to the assumption, that the the processor knows
that the return value is never used and as a result doesn't invoce the EJB
method at all.


My question:

Is there some kind of argument I can set (at the delegation's output element)
to tell the delegation to ignore a potential return value or that there'll
never be a return value (cause it's a void method)?


Thanks in advance for your help.


new-message.xpl:

<?xml version="1.0" encoding="utf-8"?>
<p:config xmlns:p="http://www.orbeon.com/oxf/pipeline"
...>

  <p:param type="input" name="instance"/>

  <p:processor name="oxf:xslt">
    <p:input name="data" href="#instance"/>
    <p:input name="config">
      <xsl:stylesheet version="2.0"
          xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
        <xsl:template match="/">
          <xsl:element name="delegation:execute">
            <xsl:attribute name="service">create-task</xsl:attribute>
            <xsl:attribute name="operation">createMessage</xsl:attribute>
              <model xsi:type="xs:string"><xsl:value-of select="//id"/></model>
              <model xsi:type="xs:string"><xsl:value-of
select="//message"/></model>
          </xsl:element>
        </xsl:template>
      </xsl:stylesheet>
    </p:input>
    <p:output name="data" id="sub-pipeline-config"/>
  </p:processor>

  <p:processor name="oxf:delegation">
    <p:input name="interface">
      <config>
        <service id="create-task" type="stateless-ejb" uri="FooBar_Client1"/>
      </config>
    </p:input>
    <p:input name="call" href="#sub-pipeline-config"/>
    <p:output name="data" id="ejb-data"/>
  </p:processor>

  <p:processor name="oxf:text-serializer">
    <p:input name="data" href="#ejb-data"/>
    <p:input name="config">
      <config/>
    </p:input>
  </p:processor>
</p:config>


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On Tue, Mar 11, 2008 at 8:54 AM,  <[hidden email]> wrote:
>  Is there some kind of argument I can set (at the delegation's output element)
>  to tell the delegation to ignore a potential return value or that there'll
>  never be a return value (cause it's a void method)?

What you are looking for is entirely reasonable, but right now this is
not supported. The code in DelegationProcessor does:

result = method.invoke(instance, parameterValues.toArray()).toString();

This code expects the method to return something that can be converted
to a string. This is quite limited; I agree. You have a few options to
deal with this. You can either:

* Change the method to return an empty string, and connect the output
of the Delegation processor to a null-serializer.
* Change the code of the Delegation processor to support calling
methods that don't return anything. And of course, we would really
appreciate if you can contribute back your changes.
* Use your own custom Java code to call the EJB, for instance through
the Java processor (see
http://www.orbeon.com/ops/doc/processors-java).

Alex
--
Orbeon Forms - Web 2.0 Forms, open-source, for the Enterprise
Orbeon's Blog: http://www.orbeon.com/blog/
Personal Blog: http://avernet.blogspot.com/


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Thanks for the quick response. I think my first step will be to make use
of your first suggestion (zero-string + null-serializer). But since that
will not always be possible (or at least not without writing an ugly
'wrapper' of some kind) I will definitively take a deeper look at point
2+3. Thanks again.


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