As a dev list lurker, let me say I too am "really enjoying this discussion". I'm learning a ton.
Jay http://www.vtgroup.com/ -----Original Message----- From: Don Brown [mailto:[EMAIL PROTECTED] Sent: Thursday, September 01, 2005 1:06 PM To: Struts Developers List Subject: Re: Spring and XWork in Ti Perhaps an example would help convey what I'm trying to say: Take a simple case where you want to processing time and log it to a file. As a XWork interceptor, it would look like this: long startTime = System.currentTimeMillis(); String result = invocation.invoke(); long executionTime = System.currentTimeMillis() - startTime; log.info("Execution time: "+executionTime+" ms"); Here, we define a method variable, startTime, before the rest of the execution, then need to access it after the execution is done. If we wanted to write this as a Filter in commons-chain, we couldn't without making startTime a class level variable, but then the command would no longer be thread-safe. Ah, but you might suggest we write that as a chain since a chain has explicit control over executing its children. But then, we'd have to define the rest of the commands within that chain and if you have multiple commands like this timer command, they too would have to be chains: process-chain timer-chain fooCommand otherAroundCommand barCommand .... This obviously has the disadvantage of deep nesting losing some of the readability of a simple process chain. Therefore, my point is an interceptor chain is better suited to a scalable, linear process flow, while chain is better for decision points. And neither, I'd argue, is well suited for a robust, configurable workflow, and this surely we can agree we are seeing with commons-chain in Struts Classic. Don BTW, I'm really enjoying this discussion and have missed these on this list. Ted Husted wrote: > On 9/1/05, Don Brown <[EMAIL PROTECTED]> wrote: > >>In that case, I find interceptors more practical, as they allow >>you to have code before and after processing that uses method variables. With >>Chain, you have to use a Filter and even then, there is no way to share >>variables between the two blocks of code without instance variables which has >>its own problems. > > > First, you're doing the work, Don, and so you're welcome to make the > decisions :) > > Though, I don't understand is why you'd want to be restricted to two > blocks of code :) > > With Chain, any number of blocks of code, be they commands or chains, > in any combination, can be the object of the request processing. > > In OverDrive/Nexus, we do find having interceptors that surround each > request useful. It's not hard to define "pre" and "post" chains, and > then at runtime create a third chain to execute them all. > > public void ExecuteView (IRequestContext context) > { > IRequestCommand command = VerifyRequest (context); > if (context.IsNominal) > { > IChain chain = new Chain (); > if (_PreOp!=null) chain.AddCommand (_PreOp); > chain.AddCommand (command); > if (_PostOp!=null) chain.AddCommand (_PostOp); > try > { > chain.Execute (context); > } > catch (Exception e) > { > context.Fault = e; > } > } > } > > http://svn.apache.org/viewcvs.cgi/struts/sandbox/trunk/overdrive/Nexus/Extras/Spring/Catalog.cs?view=markup > > The PreOp and PostOp chains are defined in the configuration, along > with everything else. > > But, we're not trying to solve the problems of navigational workflows, > only the problem of processing business use cases and interacting with > a presentation layer > > -Ted., > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
