When im­ple­ment­ing a ser­vice-ori­ent­ed ar­chi­tec­ture (SOA), there is al­ways the choice be­tween com­po­nents (in­clud­ed mod­ules of reusable func­tion­al­i­ty) ver­sus ser­vices (de­ployed once, reused by calls over the net­work).

How do you know which one to choose? There is a lot of things to con­sid­er, but these will give you a head-start:

• if there is a need for dif­fer­ent con­fig­u­ra­tion pa­ra­me­ters per con­sumer, fa­vor a com­po­nent
• if per­for­mance of re­mote net­work calls is prob­lem­at­ic, fa­vor a com­po­nent
• if de­ploy-once is cru­cial, fa­vor a ser­vice
• if you have no con­trol over the de­ploy­ment pa­ra­me­ters, fa­vor a ser­vice (e.g., if the provider is a third par­ty)
• to dy­nam­i­cal­ly switch be­tween both, choose ser­vice com­po­nent ar­chi­tec­ture (SCA)

Also, keep in mind that com­po­nents re­quire set­ting up the re­quired in­fra­struc­ture (data­base schema, queues, etc) for each de­ploy­ment.

Prob­a­bly most read­ers of this blog post will know about com­po­nents, be­cause you prob­a­bly use Trans­ac­tion­sEssen­tials as a com­po­nent

In an at­tempt to 'in­crease per­for­mance', many peo­ple will try to hack around in JMS - there­by falling into the idem­po­tent re­ceiv­er trap by check­ing for du­pli­cate mes­sage re­ceipt. The con­se­quence: scal­a­bil­i­ty ac­tu­al­ly de­grades!

For­tu­nate­ly, the best way to en­joy re­li­able mes­sag­ing is also the sim­plest one, and it scales lin­ear­ly.

We've up­loaded a slideshare pre­sen­ta­tion on de­vel­op­ing trans­ac­tion­al ap­pli­ca­tions with Spring. En­joy!

Here is an­oth­er ex­cel­lent ar­ti­cle about the cost of ap­pli­ca­tion servers, and why a par­a­digm shift is need­ed with lighter-weight al­ter­na­tives:

http://www.tom­ca­t­ex­pert.com/blog/2010/06/03/mi­grat­ing-jee-ap­pli­ca­tions-tom­cat-mo­ti­va­tion-mi­grat­ing

In­ter­est­ing note: the au­thor used to work at Bea, so he def­i­nite­ly knows what he is talk­ing about;-)

Check out http://www.tom­ca­t­ex­pert.com/blog/2010/07/07/how-mi­grate-jee-ap­pli­ca­tions-tom­cat for a nice dis­cus­sion on how to mi­grate from jee to a light-weight al­ter­na­tive like Tom­cat - with Atomikos for JTA if need­ed.