SaaS and J(2)EE

Introduction

Multitenancy refers to the architectural principle whereby a single instance of software runs on a software-as-a-service (SaaS) vendor’s servers, whilst serving multiple client organizations (tenants). This is in contrast to multi-instance architecture where separate software instance or hardware systems are set up for different client organizations. in other words, under a multitenant architecture, applications are required to virtually partition data and configuration so that each client organization works with a customized virtual application instance. Customization typically includes aspects like user interface branding, access control, data and configuration, workflow, etc

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What is SOA - Service Characteristics - Distributed

Services should be distributable, that is they need not and indeed should not run in the same process as the consumer. Services that run in the same process offer no possibility of runtime reuse to other consumers.

In order to achieve this goal you minimally need two things: a remoting framework and location transparency

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JBoss

I have in the past worked on Websphere and now Weblogic JEE application servers and fortunately never had to port between the two. Just porting from one version of a product to the next is difficult enough, never mind a cross product port! I have found Weblogic to be a fine product, certainly much easier to learn and use than Websphere, but its not cheap, and one of our prospective clients has raised the question of running on JBoss which is of cours open source.

“No problem!” our sales people cry and I wince. JEE is a fine thing in theory and certainly gives you a hope of porting whereas .NET gives you no such hope at all, but the problem is in those little extras that the vendors give you for competition's sake.

So I worry about those JEE implementation variations, some obvious like the Weblogic deployment specific files, some more subtle, like the way CMP works, and I worry about whether JBoss' messaging and clustering will be as tidy as Weblogic's.

So I've downloaded JBoss and will be giving it a go. Hopefully there are some migration guides and even tools out there to simplify my task, but I'm expecting tears and further hair loss.

What's worse is that I'm dying to get rid of all our EJBs, introduce Spring and Hibernate, and run in a servlet container rather than full a blown application server. That would certainly be much more portable, since with Spring you are essentially taking your application container with you. Of course then you are tied into Spring...

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Who needs an application server?

If you are primarily building web services then I would give this question serious consideration.

Why spend a fortune on expensive and complex JEE application servers when the combination of Apache Tomcat, Axis webservices (or your favourite open source alternative), Spring AOP container, ACEGI security framework, Hibernate or iBatis persistence frameworks offers a very viable and free alternative?

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