Wednesday, April 30, 2008

SOA - how does one discover services??

Lately in the SOA yahoo group, I was involved in a discussion about what one would consider a successful SOA implementation. Given that SOA really has to be considered from a business perspective, there are very few case studies out there that provide details about the business specifics of implementation. These case studies only talk about the integration of various systems. Very disappointing and frustrating for people to learn from.

A successful implementation of Business SOA really has to outline and give details about the process of service discovery (business services more specifically) and how an organization goes about outlining the Service architecture map that helps it to zoom in on those services that provide strategic /tactical advantage versus ones that are more utility services and could probably be bought. KPIs around these business services would then help the organization measure the benefits of these business services in the strictest sense in line with its strategies.

So, as I research on SOA, those interesting case studies elude me - however the best source of material I've come across has been from Steve Jones (CTO, CapGemini). In general though, service discovery comes very close to the methodology of discovering domain objects in an enterprise wide system. As Steve has eloquently put - services tend to be around functional nouns, so "Order Management" is a good example, it will have capabilities that are the verbs "newOrder","createDispatch", etc and it will have priorities for its operation e.g. availability, response times, dispatch sizes etc.

It definitely seems like OO design, however this discovery has to be top-down, with business folks heavily involved throughout service discovery. Most organizations struggle with that, but maybe there's light at the end of the tunnel as the industry gets a better understanding and feel for SOA and what such undertakings really require an organization to do.

Thursday, April 24, 2008

Liking Spring 2.5 (love annotations)

Ok, I think I feel comfortable in adopting or suggesting the Spring framework for JEE projects. And I am sure some people would say that they had reached that conclusion a long time ago. However, earlier I would tend to disagree on a couple of counts if someone suggested that Spring was the best thing to happen to Java and a better alternative to the existing JEE spec. The things I despised about Spring earlier were:
  • Too many libraries to include
  • Too much in an Xml configuration leading to some tricky runtime debugging errors
However, the Spring folks seem to have taken notice and have addressed these problems with Spring 2.5. So at my first opportunity, I decided to code with Spring 2.5 leveraging it mainly for its annotation facility. A really good resource I found for seeing the customization of Spring's annotation features is on InfoQ. However, I also extended a couple of the classes in Spring to be able to mimic resource manager injection capability (aka autowiring), similar to JPA persistent manager injection in JEE 5. The code looks something like this:

public class WiredBean
private Resource resource;

public boolean isInjected()
if ( resource!=null )
return true;
return false;

Spring allows renaming of annotations so that there is no dependency in your code on Spring classes. However to be able to inject (or autowire objects) based on your own annotation, requires some coding and essentially the following 2 things -
  1. Create your own class that extends InstantiationAwareBeanPostProcessorAdapter ( look at PersistenceAnnotationBeanPostProcessor for an example or email me for my example)
  2. Your Sping xml configuration needs really only 2 entries:
    1. An entry to register your own AnnotationBeanPostProcessor
    2. An entry to scan for your own autowiring annotation that allows one to override default behavior.
And you'll get code that looks like the above. Injecting your own manager objects into a JEE 5 application could be done using a Filter on the web side and Interceptors on the service/ejb side. If you are in an organization that wishes to avoid direct dependency on Spring all over the place in their JEE apps, custom annotations as I've mentioned allows for that separation.