Page History

...

• starting dependent services; where a parent component is dependent on the child components starting; where the start process may be asynchronous in different threads. e.g. there may be a recovery process on startup which you need to wait for.
• implementing master-slave type protocols where you need to monitor the state of the master and slave to make decisions on what to do; together with dealing with transitions from Started to Recovering to Running then maybe to FailingOver etc.
• implementing message orchestration. You may want to implement some simple orchestrations, waiting for either a response to arrive or a timeout to fire etc

Code overview

First we'll give an overview of the two main interfaces in BeanFlow then we'll progress to concepts like timeouts and composing activities.

State class

We have a State<T> interface which is identical to the AtomicReference<T> interface included in java.util.concurrent in Java 5 apart from that it allows you to register listeners to the state. This makes it easy to respond to the changes in state.

...

The default notifier used is the SynchronousNotifier but its easy to switch to an AsynchronousNotifier by just passing it into the constructor of the State<T> object.

Activity class

An activity is just a POJO which implements the Activity interface; it has a simple lifecycle, you can start them and stop them and ask their status.

...