demo.howto
Class DDHowto

java.lang.Object
  |
  +--ostore.util.StandardStage
        |
        +--demo.howto.DDHowto

All Implemented Interfaces:

EventHandlerIF, SingleThreadedEventHandlerIF

public class DDHowto

extends StandardStage

implements SingleThreadedEventHandlerIF

A simple example of how to write your own DD client and message types. The example is as follows. We bring up two machines, a sender and a receiver. The sender sends a DDHowto.Ping message to the receiver, which the receiver acknowledges with a DDHowto.Pong. This happens a number of times, and then the test exits. It's simple, but it covers most of the things you need to know to do more complicated things. Please just read the source, it's well commented.

First off, this class is going to be a SEDA/Sandstorm stage, so it has to inherit from SingleThreadedEventHandlerIF.

Version:

$Id: DDHowto.java,v 1.3 2004/05/19 06:33:43 hweather Exp $

Author:

Sean C. Rhea

Nested Class Summary

static class	DDHowto.Ping One of two DD messages used in this test.
static class	DDHowto.Pong This class is identical in all by type from the DDHowto.Ping class, so I'm not going to comment it further.

Field Summary

Fields inherited from class ostore.util.StandardStage

classifier, DEBUG, event_types, inb_msg_types, logger, my_node_id, my_sink, outb_msg_types, resender, resender_tokens, serializable_types, sim_running, tag

Constructor Summary

DDHowto()
Constructor: Creates a new DDHowto stage.

Method Summary

void	handleEvent(QueueElementIF item) This is the function that will be called when a stage dispatches a message that we've subscribed to.
void	init(ConfigDataIF config) Specified by seda.sandStorm.api.EventHandlerIF Initializes the stage once Sandstorm is up and running or more likely DustDevil (a.k.a. a Little SandStorm [lss]) You'll notice that most stages won't have constructors.

Methods inherited from class ostore.util.StandardStage

BUG, BUG, BUG, destroy, dispatch, enqueue, handleEvents, now_ms, now_us

Methods inherited from class java.lang.Object

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

Constructor Detail

DDHowto

public DDHowto()
        throws Exception

Constructor: Creates a new DDHowto stage.

Method Detail

init

public void init(ConfigDataIF config)
          throws Exception

Specified by seda.sandStorm.api.EventHandlerIF Initializes the stage once Sandstorm is up and running or more likely DustDevil (a.k.a. a Little SandStorm [lss])

You'll notice that most stages won't have constructors. The reason is that all initialization can take place here, where you have the information from your stage's config file to help you. I'll detail the important things you want to do in this function below.

Specified by:

init in interface EventHandlerIF

Overrides:

init in class StandardStage

Exception

handleEvent

public void handleEvent(QueueElementIF item)
                 throws EventHandlerException

This is the function that will be called when a stage dispatches a message that we've subscribed to.

Specified by:

handleEvent in interface EventHandlerIF

EventHandlerException