org.lightwolf
Class FlowSignal

java.lang.Object
  java.lang.Throwable
      java.lang.Exception
          java.lang.RuntimeException
              org.lightwolf.FlowSignal

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

DelayedCallSignal, SuspendSignal

public abstract class FlowSignal
extends RuntimeException

The root of all signal classes. A signal is sent to the flow-controller by the Flow.signal(FlowSignal) method. Because the signal is an exception, it must be caught by the flow-controller in a catch block. The following snippet is an example of signal handling:

     void startFlow() { // This is the flow-controller. 
         try {
             runFlow(); // Runs the flow, which might send a signal.
             System.out.println("The flow finished normally.");
         } catch (FlowSignal signal) {
             // A signal was sent.
             signal.defaultAction(); // Calls the signal's default action.
             System.out.println("The flow is waiting for something.");
         }
     }

     @FlowMethod
     void runFlow() { // This is the flow-creator.
         ...
     }
 

A well-behaved signal handler should call the signal's defaultAction() method, like the above example. For more information about sending and handling signals, please check the Flow.signal(FlowSignal) method.

Author:

Fernando Colombo

See Also:

Serialized Form

Constructor Summary

FlowSignal()

Method Summary

abstract void	defaultAction() The signal's default action.
Flow	getFlow() The flow that have sent this signal, or null if this signal was just instantiated and not sent yet.
Object	getResult()

Methods inherited from class java.lang.Throwable

fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

FlowSignal

public FlowSignal()

Method Detail

getFlow

public final Flow getFlow()

The flow that have sent this signal, or null if this signal was just instantiated and not sent yet. While the signal is being handled, it is guaranteed that the flow will be in suspended state.

getResult

public Object getResult()

defaultAction

public abstract void defaultAction()

The signal's default action. The behavior of this method varies and is defined by the actual signal class. Usually this method registers the flow somewhere, so it can be resumed when a certain event happens. A well-behaved flow-controller should always call this method while handling a signal.

NOTE TO IMPLEMENTORS: Document well what the implementation of your method does, specially on the method's JavaDoc. You can call getFlow() to obtain the flow that have sent the signal. Inside this method, it is guaranteed that the flow will be in suspended state.