JMS

I, Nitol and Paul are 3 developers who worked at the early times of our career as java developers in a project named SPRINTRE in Bangladesh almost 6 years back. Coincidentally, we all 3 are now in USA. I and Nitol in California and are now neighbours and Paul just came to USA few weeks back and interviewing for openings in New York area. This is a part of a technical discussion going amongst us in JMS that Nitol sent. I am keeping it here finding valuable for reference.

Excerpt From Nitol’s Email

JMS is not mandatory thing, it’s a tool. If it properly used, then it can be useful. It helps to modularize code, improves maintainability …

I’m going to describe one scenario from project Spintre, you remember right :). When a Purchase Order is approved, it should be saved in the PO table also it should save one record in accounts in proper cost center. How did we implemented it, we had accounts service call in PO module. Means we made PO module dependent on accounts module. Suppose we had a ActivityTracking module, which saves all user activity. How did we implemented it? We would have implemented it by calling activity tracking service. Suppose we have to include notification service also, when ever a PO is approved, purchase officer wants a email in his email box.

accountService.save(amount, costcenter);

activityTrackingService(userObj, PoModuleIdentifier, ActivityApprove ..);

{

look for who want’s notification, get the email address and send the email.

}

How do you like this code implementation? How is the impression of a User who just clicked on the Approve button and waiting for so many thing to happen.

Those all service can be asynchronous, those activity don’t need to be real time. Now how we can use JMS here

when PO is saved, code block using JMS is

{

Event event  = new Event(po number, date, Module, ActivityType, user ……)

jmsPublisher.publish(event);

}

Done, clean implementation. But now we can write sevaral Subscriber

AccountModuleSubscriber {

receive(Message obj) {

Event event = (Event) obj;

// save it to correct cost center

}

}