Why I have to use message composer for casting StringReader to String?

[apodhrad]

Hi folks,

when trying to expose a BPMN proces via HTTP I get the following error:

org.switchyard.HandlerException: org.jbpm.workflow.instance.WorkflowRuntimeException: [com.sample.bpmn.hello:1 - Hello:2] -- java.io.StringReader cannot be cast to java.lang.String

Yes, I can use the message composer for casting StringReader to String but I'm wondering why? When I do the same with simple bean it is working without the composer.

Please see my two projects http-bean and http-bpmn (also includes the message composer but it isn't set).

Andrej

[kcbabo]

Bottom line is that this is a sorta-bug in the HTTP binding.  The message composer for HTTP should check the message type defined for the operation to determine if a Java type is used.  If it is, then the HTTP composer should attempt a conversion to the declared content type.  Here's an example from the composer used by all Camel bindings:

https://github.com/jboss-switchyard/components/blob/master/common/camel/src/main/java/org/switchyard/component/camel/common/composer/CamelMessageComposer.java#L61

Can you file a JIRA to have this addressed? 

In terms of why this works for you now with bean services and not with bpm - that's a side effect of how the bean implementation maps the message content to operation parameters.  The bean component uses getContent(Class<T> type), which forces the conversion from StringReader to String.  As I mentioned above, this should really happen earlier in the binding layer since the composite service interface defines a type of String, not StringReader.

[apodhrad]

Hi Keith,

thx, I reported it at [#SWITCHYARD-1674] HTTP binding cannot cast StringReader to String - JBoss Issue Tracker

Andrej