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From "Glynn, Eoghan" <eoghan.gl...@iona.com>
Subject RE: When should we close the handlers in CXF?
Date Fri, 19 Jan 2007 10:41:57 GMT
 

> -----Original Message-----
> From: Liu, Jervis [mailto:jliu@iona.com] 
> Sent: 19 January 2007 07:34
> To: cxf-dev@incubator.apache.org; cxf-dev@incubator.apache.org
> Subject: RE: When should we close the handlers in CXF?
> 
> Hi,
>  
> Did we have any previous discussions on why we wont want a 
> JAX-WS like APIs for interceptor chain? 

Yes, I've brought this up a few times before, e.g. see point #4 in this
cxf-dev post [1] from Nov 10th last.

My problem with the CXF Interceptor.handleFault() method is that it
actually has semantics closer to the JAX-WS Handler.close(), and is
gratuitously different from the similarly-named Handler.handleFault()
method .

I've argued that is needlessly confusing for developers who use both the
CXF Interceptor and JAX-WS Handler APIs, and we should in fact model the
former on the latter.

> I.e., an Interceptor 
> interface should look like below:
>  
> public interface Interceptor<T extends Message> {
>     void handleMessage(T message) throws Fault;
>     void handleFault(T message);
>     void close(T message);    
> }

If we were to include *both* handleFault() and close() on Interceptor,
then the current Interceptor.handleFault() semantics would have to
change.

My proposal in the above referenced mail was to change handleFault()
semantics as follows:

"[currently] when a fault occurs on the in-chain, we unwind the current
chain by calling
handleFault() on each previously traversed interceptor and then jump to
the out-fault-chain,
calling handleMessage() on each interceptor with the fault message. I'd
propose changing this
to drop the unwind, instead call faultMessage() on each interceptor in
the out-fault-chain."

I suppose the unwind wouldn't be totally dropped, just achieved using
Interceptor.close() instead of handleFault().
 
> I see the possibility of removing subchains(interceptor chain 
> re-entrance) from the interceptor chain by using close 
> method. I am not saying sub-chain and the reentrance is that 
> bad, but it does bring some confusion to understand the 
> interceptor flow and it also brings unnecessary complexity 
> such as handling exceptions thrown from a subchain and how to 
> return back from subchain. Take the SOAPHandlerInterceptor as 
> example, it looks like below now with a close method:
>  
>     private OutputStream oldStream;
>     ......
>     public void handleMessage(SoapMessage message) {
>         if (getInvoker(message).getProtocolHandlers().isEmpty()) {
>             return;
>         }
>         if (getInvoker(message).isOutbound()) {
>             oldStream = message.getContent(OutputStream.class);
>             CachedStream cs = new CachedStream();
>             message.setContent(OutputStream.class, cs);
>         } else {
>            .....
>         }
>     }
> 
>     public void close(SoapMessage message) {
>         if (getInvoker(message).isOutbound()) {
>             super.handleMessage(message);
>             try {
>                 CachedStream cs = 
> (CachedStream)message.getContent(OutputStream.class);
>                 // Stream SOAPMessage back to output stream 
> if necessary
>                 SOAPMessage soapMessage = 
> message.getContent(SOAPMessage.class);
>                 if (soapMessage != null) {
>                     soapMessage.writeTo(oldStream);
>                 } else {
>                     cs.flush();
>                     AbstractCachedOutputStream csnew = 
> (AbstractCachedOutputStream) message
>                             .getContent(OutputStream.class);
>                     AbstractCachedOutputStream.copyStream(csnew
>                             .getInputStream(), oldStream, 64 * 1024);
>                     cs.close();
>                 }
>                 oldStream.flush();
>                 message.setContent(OutputStream.class, oldStream);
>             } catch (IOException ioe) {
>                 throw new SoapFault(new 
> org.apache.cxf.common.i18n.Message(
>                         "SOAPHANDLERINTERCEPTOR_EXCEPTION", 
> BUNDLE), ioe,
>                         message.getVersion().getSender());
>             } catch (SOAPException soape) {
>                 throw new SoapFault(new 
> org.apache.cxf.common.i18n.Message(
>                         "SOAPHANDLERINTERCEPTOR_EXCEPTION", 
> BUNDLE), soape,
>                         message.getVersion().getSender());
>             }
>         } 
>     }
> 
>  
> We can do the same thing for MessageSenderInterceptor, 
> StaxOutInteceptor and SoapOutInterceptor etc.
>  
> Does this look good to everyone, any thoughts?

Just so I'm sure I understand correctly, are you proposing to use
close() to trigger a jump from the sub-chain back up to the main chain?

If so, where is this jump done currently?

Cheers,
Eoghan

[1]
http://mail-archives.apache.org/mod_mbox/incubator-cxf-dev/200611.mbox/%
3cFA1787F64A095C4090E76EBAF8B183E071FADE@emea-ems1.dublin.emea.iona.com%
3e

> Cheers,
> Jervis
> 
> ________________________________
> 
> From: Dan Diephouse [mailto:dan@envoisolutions.com]
> Sent: Thu 1/18/2007 9:55 PM
> To: cxf-dev@incubator.apache.org
> Subject: Re: When should we close the handlers in CXF?
> 
> 
> 
> I think the registering of actions to be run at the end of 
> the chain is good.
> 
> Another possibility is to add a close(Message) method to the 
> Interceptor which gets called at the end of the chain. If we 
> did that I would think we might want to get rid of the 
> handleFault method as cleanup could be done in close().  
> (Eoghan - I'm actually suggesting we move closer to the 
> JAX-WS APIs! ;-))
> 
> Thoughts?
> 
> - Dan
> 
> On 1/18/07, Glynn, Eoghan <eoghan.glynn@iona.com> wrote:
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: Unreal Jiang [mailto:sinbad_jia@yahoo.com]
> > > Sent: 18 January 2007 11:44
> > > To: cxf-dev@incubator.apache.org
> > > Subject: RE: When should we close the handlers in CXF?
> > >
> > > Hi Eoghan,
> > >   I think those two approach are work fine.
> > >
> > >   The first approach is only for handlers process,
> > >   The second approach can do some clean-up works not only for 
> > > handlers  but interceptors,  but if we use runnable object for  
> > > TerminalAction,  the order of handlers or interceptors 
> will be  hard 
> > > to ensure.
> >
> > In most cases, a FIFO ordering of the terminal actions 
> would be fine, 
> > i.e. the order in which the terminal actions are executed would 
> > reflect the order in which the interceptors were traversed. If you 
> > needed more fine-grained control, maybe 
> > InterceptorChain.addTerminalAction() could be replaced by 
> something like ...
> >
> > interface InterceptorChain {
> >     List<Runnbale> getTerminalActions(); }
> >
> > ... so that the code submitting the terminal action could control 
> > ordering with respect to previously submitted terminal 
> actions. Going 
> > even further that this (e.g. something akin to the
> > PhaseInterceptor.getBefore/After() business) would I think 
> be overkill 
> > without a specific ordering-sensitive usecase.
> >
> > However, a closer look at the JAX-WS HandlerChainInvoker 
> code suggests 
> > that only one of the LogicalHandlerInterceptor and 
> > SOAPHandlerInterceptor will actually need to submit a 
> terminal action.
> > So with only a *single* terminal action concerned with closing 
> > handlers, ordering shouldn't be an issue here.
> >
> > This is because the same HandlerChainInvoker instance is shared by 
> > these two interceptors, and the code that calls 
> handleMessage/Fault() 
> > on the individual Handlers also adds each of these to a 
> separate list
> > (closeHandlers) of handlers for which close() should be called.
> >
> > Only a single call to HandlerChainInvoker.mepComplete() is then 
> > actually required to ensure that *all* the traversed handlers are 
> > close()d in the correct order.
> >
> > So maybe the simplest approach would be be to submit the terminal 
> > action in AbstractJAXWSHandlerInterceptor.getInvoker(), i.e.:
> >
> >     protected HandlerChainInvoker getInvoker(final T message) {
> >         HandlerChainInvoker invoker =
> >             message.getExchange().get(HandlerChainInvoker.class);
> >         if (null == invoker) {
> >             invoker = new 
> HandlerChainInvoker(binding.getHandlerChain(),
> >                                               isOutbound(message));
> >             message.getExchange().put(HandlerChainInvoker.class,
> > invoker);
> >
> >             // submit a *single* terminal action for entire handler 
> > chain
> >             message.getInterceptorChain().addTerminalAction(new
> > Runnable() {
> >                 public void run() {
> >                     mepComplete(message);
> >                 }
> >             }
> >         }
> >         //...
> >     }
> >
> > Cheers,
> > Eoghan
> >
> > >   So I incline to  the second approach, but we should use 
> some other 
> > > way to instead of runnable object.
> > >
> > >   Regards
> > >   Unreal
> > >
> > > "Liu, Jervis" <jliu@iona.com> wrote:I  would vote for the second 
> > > approach. When its there, we can probably use  the 
> similiar approach 
> > > to remove the sub-chain (interceptor chain
> > > reentrance) wherever it is possible.
> > >
> > > ________________________________
> > >
> > > From: Glynn, Eoghan [mailto:eoghan.glynn@iona.com]
> > > Sent: Wed 1/17/2007 9:42 PM
> > > To: cxf-dev@incubator.apache.org
> > > Subject: RE: When should we close the handlers in CXF?
> > >
> > >
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Glynn, Eoghan [mailto:eoghan.glynn@iona.com]
> > > > Sent: 17 January 2007 12:34
> > > > To: cxf-dev@incubator.apache.org
> > > > Subject: RE: When should we close the handlers in CXF?
> > > >
> > > >
> > > > Hi Unreal,
> > > >
> > > > One point to note is that all the other JAX-WS Handler touch 
> > > > points are driven through a set of interceptors, each wrapping a
> > > chain of a
> > > > particular Handler type (logical, protocol etc.).
> > > >
> > > > So for example the SOAPHanderInterceptor takes care of 
> calling the
> > > > handleMessage/Fault() methods of any SOAPHandlers in the chain.
> > > > Similarly there's a *separate* LogicalHandlerInterceptor that 
> > > > traverses the chain of LogicalHandlers. I'm guessing you
> > > already know
> > > > all this ...
> > > >
> > > > But the point is that it would be a good idea to maintain
> > > the pattern
> > > > of wrapper-interceptor calling out to JAX-WS Handler, and
> > > obviously it
> > > > would be badness to for example put this JAXWS-specific
> > > logic into the
> > > > ClientImpl code.
> > > >
> > > > However, because Handler.close() should only be called 
> at the very
> > > > *end* of the interceptor chain tarversal, and because 
> we currently 
> > > > have
> > > > *multiple* interceptors wrapping the JAX-WS Handler chains
> > > of various
> > > > types, the close() call should not be made from within the 
> > > > existing wrapper interceptors. Otherwise we'd end up with for
> > > example close()
> > > > called prematurely on the SOAPHandlers *before* the 
> > > > LogicalHandlers have even been traversed (inbound on 
> the client-side).
> > > >
> > > > So we'd need a *single* new wrapper interceptor, positioned
> > > at the end
> > > > of the in & fault-in interceptor chains, that's responsible for 
> > > > calling
> > > > close() on all types of handler. This could be driven via a 
> > > > pattern similar to the
> > > > LogicalHandlerInterceptor.onCompletion() method (e.g. the new 
> > > > interceptor walks back along the chain to find the 
> > > > LogicalHandlerInterceptor & SOAPHandlerInterceptor and calls
> > > > onCompletion() on these).
> > >
> > > On second thoughts, maybe a cleaner may of doing this 
> would be allow 
> > > an interceptor to register some sort of terminal action with the 
> > > InterceptorChain to be executed when the chain traversal is 
> > > complete, e.g.
> > >
> > > public interface InterceptorChain {
> > >     void addTerminalAction(Runnable r);
> > >
> > >     //...
> > > }
> > >
> > > Or alternatively take the Runnable as a return value from 
> > > Interceptor.handleMessage/Fault().
> > >
> > > Then in the InterceptorChain impl, run all the
> > > TerminalAction(s) from a finally block, e.g.
> > >
> > > public class PhaseInterceptorChain {
> > >    public boolean doIntercept(Message m) {
> > >        try {
> > >            while (interceptorIterator.hasNext()) {
> > >                interceptorIterator.next().handleMessage(m);
> > >            }
> > >        } finally {
> > >            for (Runnable r : terminalActions) {
> > >                r.run();
> > >            }
> > >        }
> > >    }
> > > }
> > >
> > > Then for example the
> > > LogicalHandlerInterceptor.handleMessage() would end with 
> some logic 
> > > like:
> > >
> > >    if (isRequestor(message) && (isOneway(message) ||
> > > !isOutbound(message))) {
> > >       message.getInterceptorChain().addTerminalAction(new 
> Runnable() {
> > >           public void run() {
> > >               getInvoker(message).mepComplete(message);
> > >           }
> > >       }
> > >    }
> > >
> > > Similarly for SOAPHandlerInterceptor etc.
> > >
> > > Cheers,
> > > Eoghan
> > >
> > >
> > >
> > >
> > >
> > > ---------------------------------
> > > Cheap Talk? Check out Yahoo! Messenger's low PC-to-Phone 
> call rates.
> > >
> >
> 
> 
> 
> --
> Dan Diephouse
> Envoi Solutions
> http://envoisolutions.com 
> <https://bosgate2.iona.com/http/0/envoisolutions.com>  | 
> http://netzooid.com/blog 
> <https://bosgate2.iona.com/http/0/netzooid.com/blog> 
> 
> 
> 

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