Yes, as already confirmed. One area where web services are used is standardizing how multiple applications can retrieve the same type of data from different servers. For example, if you have multiple servers that produce gridded weather data, all the data producers could get together and define a common XML schema for requesting data from their servers that they all implement. This way, clients can use different data providers interchangably. This XML schema standardization is a very fluid process that can be subject to many changes. It is easiest if your application is as isolated as possible from the actual XML schema.
Gotcha. This is clear in my mind now. The only concern I might have, and believe me I know how weird this going to sound, is that this might make it TOO flexible!
What I mean is, I think there are products already out there better suited to deal with more complex service requests, and with regard to other discussion points in this thread, if your to a point where you are exposing more complex things, as in your weather example, I'd be willing to bet you probably wouldn't consider doing it with this anyway, regardless of whether I added the transofmration capabilities or not. You would probably be talking directly to your real business objects and not wanting to go through the Actions, and then there are far better ways to do things than this.
I'm certainly not ruling out what your saying, your've definitely convinced me of the benefit it would bring, but I do see it as something for down the road because I get the feeling it really morphs what I'm doing into a much grander plan. I certainly dion't mind grand plans, and don't mind working to make those plans a reality, but I'm not as convinced that it fits in with the simple model I started with, and so it might be an addition after the more basic model is solidified.
The problem with just using a JSP is you need to write a JSP for each action. If you use auto-generated XML, you can define a smaller number of XSL stylesheets to match common XML elements for transformation. Furthermore, the pipeline approach allows you to break up the transformation process to support transformation stages that may involve more complex processing.
Actually, as it stands now you would only have to write a JSP for any responses that can't be described by the default JSP. It's hard to say how many situations would really require a custom JSP, but my gut tells me that it's probably no better than 50/50 in favor of creating a new JSP. My bet is that half the time, and maybe even more, the default template will suffice, probably with the member list attribute in use more times than not. Granted, if your response has to work within the confines of a defined schema as in your weather example, then your talking a new JSP, and then that becomes a burden most likely. But again, it your doing something like that, I suspect you'd have decided against my little package already!
Again I think this is somethng that I can see where the benefit comes in, but probably baloons the complexity again. I can concieve of this project expanding as time goes on to more "compete" with the more developed packages out there now, but I feel like that's a much more long-term goal than what I'm trying to accomplish now.
While struts-chain won't be incorporated into Struts until probably 1.3 (but could be somewhere in 1.2), it is still available to be used with Struts 1.1. Since you are requiring a custom request processor anyways, just use the struts-chain request processor and refactor your capabilities into multiple commands instead of extended RequestProcessor methods. The burden on your users will be about the same and the transition to future Struts will simply require you to discontinue the specific use of the chain's legacy RequestProcessor. Your function code will already be in commands that are already compliant.
That sounds good, I will definitely look into doing it this weekend. Your comments above alay whatever fears I might have had, it sounds like the right thing to do overall, and not a massive change either.
Good job with what you've put together so far. I think this extension is a great addition to the toolbox available to Struts developers.
Thank you, I'm very glad to hear the positive feedback I've gotten, and just as happy that people are interested enough to at least make suggestions and question what I'm doing. Any comments, regardless of what side of the fence they are on or if/when I act on things is valuable. I was concerned that I was the only one that thought this might be something useful, but it sounds like I'm not alone, and that certainly motivates me to develop it further.
Don
Thanks!
Frank
From: Don Brown <[EMAIL PROTECTED]> Reply-To: "Struts Developers List" <[EMAIL PROTECTED]> To: Struts Developers List <[EMAIL PROTECTED]> Subject: Re: Struts Web Services Enablement Project Date: Fri, 04 Jun 2004 12:14:16 -0400
I think there can be considerable benefit from exposing Struts Actions. For one, how Struts is currently architected, all the validation happens in the Struts layer so putting the web service interface in front of that makes sense. Two, many times user authorization occurs in the Actions and so if this code hooked into the Servlets API, authorization is automatically taken care of.
I'd recommend two feature additions to make this useable for document style SOAP messaging:
1) Put a configurable XML transformation pipeline before the SOAP message gets interpreted for parameters, and after the response is created. The pipeline for the response should start with auto-generated request XML (via something like XStream).
2) Improve the request parameter schema for the incoming XML document to include XPath paths as parameter names. This way, using something like JXPath, a complex XML element could be automatically created, to be then transformed by the pipeline. Send the resulting XML to the action via a wrapper action form or even just put it in the request. Better yet, have the resulting XML be processed by an XML binding framework like XStream to create arbitrary Java objects to be passed to the action.
The key is to enable any XML schema to be used as input and output. The XML pipeline further isolates you from schema changes.
Finally, I'd also recommend looking at using struts-chain rather than a RequestProcessor. If the above functionality was decomposed into different Commands, one could easily plug in, say, a different XML binding framework or get rid of the XPath processor altogether.
Don
Duncan Mills wrote:
Didn't mean to be harsh - I was just presenting the alternative viewpoint that has to be answered. Personally I can see the benefit that this project could offer, but the counter stance is a one to raise is it not?
Regards
Duncan Mills Senior Principal Product Manager Oracle Application Development Tools
Jung, Eric wrote:
Wow, that's kind of harsh, Duncan.
-----Original Message----- From: Duncan Mills [mailto:[EMAIL PROTECTED] Sent: Friday, June 04, 2004 3:38 AM To: Struts Developers List Subject: Re: Struts Web Services Enablement Project
Frank forgive me here, but playing Devils Advocate, if you have clean MVC separation then surely the last thing you want to do is to expose Actions as Web Services.
It is reasonable to want to expose Business Service Providers such as EJB, or TopLink beans as Web Services but that's up in the model layer, what's the point in pushing the access point down into the Controller code?
Or do you see here a solution for all those folks who've not followed best practice and have intermingled Controller functionality with Business logic..?
Regards
Duncan Mills Senior Principal Product Manager Oracle Application Development Tools
Frank Zammetti wrote:
Hello devs! This is my first time posting here, and my first attempt at contributing to an Apache project. I hope I'm going about it properly! :)
In short, I have a little project going with the stated goal of allowing a Struts developer to expose any existing business logic, as implemented in Struts Actions and their subordinate helper classes, as Web Services, and do this with NO changes required to any existing application code, and as little change to Struts itself as possible. Simplicity is the key to this!
Today I released a second version of this project to the user's mailing list, and after some feedback I think it's at a point where I'd like to make you all aware of it, and get some higher-level feedback. It's certainly far from complete at this point, but I think even now it's in a useful form.
My hope is that eventually it will be good enough to be included in the base Struts distro, but that's obviously a long way off, if ever.
With all that in mind, please at your convenience visit http://www.omnytex.com/strutsws
There you will find some more detailed technical information and a download which contains everything you need, including a simple sample webapp demonstrating the whole mess.
I thank you in advance for any time you spend on this!
Frank W. Zammetti
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