Re: Bypassing unnecessary transforms by Tuscany databinding framework

[Raymond Feng]

+1 on the proposal.

The interceptor could just return the flag based on its capability without 
asking the next one. And the runtime can query it from the head in the 
invocation chain and stop when it gets a true.

boolean allowsPBR = false;
Invoker i = invocationChain.getHead();
while(i!=null) {
   if(i instanceof PassByValueInvoker}
   {
       if((PassByValueInvoker) i).allowsPassByReference()) {
           allowsPBR = true;
           break;
       }
       if(i instanceof Interceptor) {
           i = ((Interceptor) i).getNext();
       }
   }
}

Thanks,
Raymond

----- Original Message ----- 
From: "Jean-Sebastien Delfino" <[EMAIL PROTECTED]>
To: <tuscany-dev@ws.apache.org>
Sent: Thursday, February 07, 2008 6:06 PM
Subject: Re: Bypassing unnecessary transforms by Tuscany databinding 
framework


Raymond Feng wrote:
One more question:

Do you think if the participants to enforce PBV know their data 
capability upfront (static) or do they have to defer the decision to the 
actual invocation time (dynamic)? It seems that you were leaning to the 
dynamic style in your proposal.

Static, per operation.


If it's static, we could have a flag set on the InvocationChain (instead 
of Message and Interceptor). The implementation/binding providers as well 
as other interception providers can call InvocationChain.setPBVEnsured().

A flag on interceptor will let its implementor decide the value of the 
flag according to what he's doing in the interceptor. That's more 
extensible than hardwired logic in the providers competing to set a single 
flag.

With my latest proposal we don't even need a message flag as an 
interceptor that copies data just needs to return the flag value 
indicating that the data is now safe from changes.

To summarize, and using the spec terminology:
AnInvoker {

  boolean allowsPassByReference() {
    // example implementation
    check the @AllowsPassByReference annotation or equivalent
    indication that the given data is safe and won't be altered
  }
}

and Interceptor {

  boolean allowsPassByReference() {
    // example implementation
    boolean doIAllowThat = depends on what I do with the data
      in the interceptor;
    return doIAllowThat && next.allowsPassByReference();
  }
}

--
Jean-Sebastien

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