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Web Services newbie question  RSS feed

 
Arun Subramanian
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Ray-
Great to have you here in the forum
As someone exposed to J2EE but not at all to web services, what additional steps (in terms of new hardware, software, security etc) does one have to take to convert, say, a java application component to a web service or to put it like this, how easy or difficult is it to transform an existing software component into a web service.
Also, I work within a corporate intranet. Do we have any examples of intranet applications utilizing a web service in practice.
Lastly, is your book comprehensible for a beginner?
Thanks,
Arun.
 
Lasse Koskela
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Originally posted by Arun Subramanian:
what additional steps (in terms of new hardware, software, security etc) does one have to take to convert, say, a java application component to a web service or to put it like this, how easy or difficult is it to transform an existing software component into a web service.
You don't need any special hardware for running web services, although processing XML messages does take its toll on performance.
What you need is a runtime environment, the middleware to run your web services on top of. This can mean using an application server that supports web services APIs (WebLogic, WebSphere, Oracle9iAS, SunONE, etc) or it can mean embedding a web services "engine" into a regular J2EE application (Apache Axis).
The difficulty of converting your application into a web service depends on your application. What does your application do? What kind of an architecture it has?
 
Ray Lai
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Originally posted by Arun Subramanian:
As someone exposed to J2EE but not at all to web services, what additional steps (in terms of new hardware, software, security etc) does one have to take to convert, say, a java application component to a web service or to put it like this, how easy or difficult is it to transform an existing software component into a web service.

Apache Axis provides probably the simplest example to expose a Java apps to web services. you rename your .java, and drop it under the webapps of your Axis servlet under Tomcat or J2EE apps server. Axis will automatically generate the stub/skeleton for you. This may be too simplistic for real life situation.
My book ch 9 pp. 500-510 (section 9.4.2) shows a simple exercise (step-by-step guide) to expose a Java component to web services using Axis's utilities java2wsdl and wsdl2java. Using these utilities, developers may spend a few minutes to create a web service.
The concept of exposing Java components is simple. You expose your servlet/beans/EJB to RPC-call. Your SOAP server (e.g. Axis) will route the SOAP-RPC call automatically by binding to your Java components (pp. 93-34 section 3.4.2).
Reality check. But in real life, there are many design complexities, e.g.
* not every Java component is RPC call; you may need both synchronous (RPC-style) and asynchronous web services
* state management issues (p. 188 section 4.8.5)
* need to consider how the apps security is designed (pp. 367-317 section 7.4.1)
* data type conversion and compatibility
* what to expose/other design considerations (e.g. p. 207 section 4.8.13) - fine-grained versus coarse-grained

Also, I work within a corporate intranet. Do we have any examples of intranet applications utilizing a web service in practice.

At Sun, many intranet apps are web services, e.g. our timecard for consultants, our travel expenses, our staff benefits system, internal messaging hub, payment services with bank, etc. They have been in production for at least 2 years.
I'm aware that many production web services are for external B2B integration, e.g. Sabre's travel services. Some customers also start with intranet first, e.g. brokers/traders' desktop risk models

Lastly, is your book comprehensible for a beginner?

Yes in general. But I'd recommend other better beginner books if you're looking for a step-by-step programming book on web services. Pls refer to a separate thread I posted on the different kinds of web services books.
My book was written with 2 target groups of audience:
1. Management, who are *beginners* but want to know real life case studies or examples, or want to do a business case/ROI for web services initiatives
2. Architects or developers, who already have a hands-on beginner book, but want to delve into advanced level of mainframe integration, architecture patterns, integration patterns, or security patterns. My book will serve as a companion book or an advanced book.
However, a refresher chapter of web services basic with some hands-on exercises are provided in ch 3. A detailed case study of complete programming examples is provided in ch 8. Pls note that this has complete design details using Unified Process methodology (elaboration details). This will be good for beginners, as I have not seen much detailed design coverage in many beginners' books.
 
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