Current functionality:
There are a series of processes that have to run periodically. The most important of them is the billing process itself (the process that generates invoices), but there are many more. To do this, you need to setup a cron or other operating system (OS) managed way to call a trigger class in jbilling. This has to be done as part of the installation process and it is OS specific.

Desired functionality:
Provide build-it triggering capabilities to be configured directly in the jbilling.properties file, this way avoid any OS specific configuration.

Technical overview:
EJB provides a timer service since 2.1 (this was not implemented in JBoss when the first version of jbilling when in production). Let's take advantage of this services and let the application server take care of triggering the periodic processes.
See chapter 14 of the free PDF book 'Mastering EJB'. You can download it at www.theserverside.com.

Server tier modifications:
The class to be called is now com.sapienter.jbilling.tools.Trigger. Take a look to it. It is meant to be a standalone client program that will be calling a series of remote methods. Depending on the parameters it will run one or many processes.
So the first thing to do is to convert this class into a session bean that implements TimedObject. This means including all the xdoclet tags in the file to get the interfaces and xml entries done during the build. The 'business logic' of this class will be to setup the timer using the properties from jbilling.properties by calling TimerService.createTimer. Then the actual call to the services (now in the main method of th class) will be in ejbTimeout.

By looking at the Trigger class, you can see that there are many services being called: the first one is the billing process, followed by the ageing process and so on until the credit card expiration emails. We want the billing process to potentially be configured to run many times in a day, while all the rest of the services to run just once per day.

The following new properties will be added to jbilling.properties:
process.time=YYYYMMDD-HHmm (a full date followed by HH is the hours in 24hs format and mm the minutes).
process.frequency=X (where X is an integer >= 0 and < 1440

The fist property indicates at what time of the day the trigger has to happen for the very first time. After this first run you will need X minutes (specified by 'process.frequency') to run the trigger again. Since only the billing process can run more than once per day, we need some logic in the ejbTimout method to verify if the call is the first one of the day (where it runs all the services) or not (where it runs only the billing process).

The first property is optional. If it is not present, or its value is null, then the next trigger will happen at startup + minutes indicated in 'process.frequency'.

Client tier modifications:
Now that we have a timer bean than can periodically run the routine processes, we just need a way to kick off the whole process by invoking this session bean only once when the application server starts up. The way to do this is with a new servlet whose only purpose in life is to run once when the app server is starting and create the session bean for the trigger. You can do this by using the tag 'load-on-startup' when you declare the servlet in the web.xml file.

Database tier modifications:
N/A

Changes mostly to be done in these files:
jbilling.properties
Trigger.java
web.xml
new servlet class for application initialization

The feature is now completed. This is the change log