Hi, I would like to summarize what we have been discussed in this thread
(including Eoghan's proposal posted last Oct [1]) regarding Interceptor API
changes. Any comments would be appreciated.
Currently our Interceptor APIs look like below:
public interface Interceptor<T extends Message> {
void handleMessage(T message) throws Fault;
void handleFault(T message);
}
Also in the interceptor chain, we have a notion of sub-chain or interceptor
chain reentrance by calling message.getInterceptorChain().doIntercept(message)
or message.getInterceptorChain().doInterceptInSubChain(message).
The main issues we have with the current implementation are:
1. Fault handling. See Eoghag's email [1]
2. Sub-chain reentrance. See previous discussion in this thread.
We propose to change Interceptor API as below:
public interface Interceptor<T extends Message> {
void handleMessage(T message) throws Fault;
void handleFault(T message);
void close(T message);
}
handleFault(T message) method is used to process fault message (which is done
by handleMessage() in fault-chain currently).
close(T message) method is called on a reverse direction at the end of
interceptor chain or when a fault or exception occurs. Take the fault handling
case as an example, below is how handleFault and close work together
when a fault occurs on the in-chain, we unwind the current chain by calling
close() on each previously traversed interceptor and then jump to the
out-fault-chain, calling handleFault() on each interceptor with the fault
message.
Close method is also used to remove the sub-chain reentrance. See the
SOAPHandlerInterceptor example I posted previously.
Cheers,
Jervis
[1]
http://mail-archives.apache.org/mod_mbox/incubator-cxf-dev/200611.mbox/[EMAIL
PROTECTED]
________________________________
From: Glynn, Eoghan [mailto:[EMAIL PROTECTED]
Sent: Fri 1/19/2007 6:41 PM
To: [email protected]
Subject: RE: When should we close the handlers in CXF?
> -----Original Message-----
> From: Liu, Jervis [mailto:[EMAIL PROTECTED]
> Sent: 19 January 2007 07:34
> To: [email protected]; [email protected]
> 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/%
<https://bosgate2.iona.com/http/0/mail-archives.apache.org/mod_mbox/incubator-cxf-dev/200611.mbox/%>
[EMAIL PROTECTED]
3e
> Cheers,
> Jervis
>
> ________________________________
>
> From: Dan Diephouse [mailto:[EMAIL PROTECTED]
> Sent: Thu 1/18/2007 9:55 PM
> To: [email protected]
> 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 <[EMAIL PROTECTED]> wrote:
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: Unreal Jiang [mailto:[EMAIL PROTECTED]
> > > Sent: 18 January 2007 11:44
> > > To: [email protected]
> > > 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" <[EMAIL PROTECTED]> 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:[EMAIL PROTECTED]
> > > Sent: Wed 1/17/2007 9:42 PM
> > > To: [email protected]
> > > Subject: RE: When should we close the handlers in CXF?
> > >
> > >
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Glynn, Eoghan [mailto:[EMAIL PROTECTED]
> > > > Sent: 17 January 2007 12:34
> > > > To: [email protected]
> > > > 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>
> <https://bosgate2.iona.com/http/0/envoisolutions.com> |
> http://netzooid.com/blog <https://bosgate2.iona.com/http/0/netzooid.com/blog>
> <https://bosgate2.iona.com/http/0/netzooid.com/blog>
>
>
>
