jorgecavaco / simple-event-loop

Java event loop for simple projects

Simple Event Loop

This is a simple event loop for multi-threaded java application. Get it from Maven repository

<dependency>
   <groupId>com.github.induwarabas</groupId>
   <artifactId>event-loop</artifactId>
   <version>1.0.0</version>
</dependency>

An event loop has its own java Thread and all callbacks are triggered in that thread context. It also contains a transfer queue implementation.

###Communicating between two threads. Communicating between two threads is simple. No locks required. Here is a sample code to send an object to the event loop.

// Creating new event loop
SimpleEventLoop s1 = new SimpleEventLoop();

// Starting. This will create a new thread.
s1.start();

// Add event handler for the event loop. This will receive Objects queue from anywhere.
s1.addEventHandler(new SimpleEventHandler() {
	@Override
	public void onEvent(SimpleEventLoop eventLoop, Object data) {
		if (data instanceof String) {
			// The String sent from main thread will receive here
			System.out.println("Received: " + data.toString());
		}
	}
});

// Sending String from main thread.
s1.queue("Hello");

###Creating timers You can create timers in both singleShot and repeatable ways.

#####Single Shot timers. These timers will call only once and these are not repeatable.

// Creating new event loop
SimpleEventLoop s1 = new SimpleEventLoop();

// Starting. This will create a new thread.
s1.start();

// Creating a timer
SimpleTimer timer = s1.createTimer(new SimpleTimerCallback() {
	@Override
	public void onTimer(SimpleTimer timer) {
		System.out.println("I am in the timer");
	}
});

// Specify time interval in milliseconds and call singleShot
timer.singleShot(1000);

#####Repeating timers These timers will repeat until stop it.

// Creating new event loop
SimpleEventLoop loop = new SimpleEventLoop();

// Starting. This will create a new thread.
loop.start();

// Creating a timer
SimpleTimer timer = loop.createTimer(new SimpleTimerCallback() {
	@Override
	public void onTimer(SimpleTimer timer) {
		System.out.println("I am in the timer");
	}
});

// Specify time interval in milliseconds call start
timer.start(1000);

###Sleeping in events If you call Thread.sleep in event callbacks, the event loop will get blocked. All other events will not trigger until you wake. But sometimes you may need to give a change to process another event while sleeping. You can do it by calling the sleep function of the event loop. See the difference of two scenarios.

#####Scenario 1. Sleeping with Thread.sleep

// Creating new event loop
SimpleEventLoop loop = new SimpleEventLoop();

// Starting. This will create a new thread.
loop.start();

// Creating a timer
SimpleTimer timer1 = loop.createTimer(new SimpleTimerCallback() {
	@Override
	public void onTimer(SimpleTimer timer) {
		System.out.println("I am going to sleep in timer 1");
		try {
			Thread.sleep(5000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("I waked in timer 1");
	}
});
timer1.start(10000);

// Creating another timer
SimpleTimer timer2 = loop.createTimer(new SimpleTimerCallback() {
	@Override
	public void onTimer(SimpleTimer timer) {
		System.out.println("Grrrrr");
	}
});
timer2.start(1000);

Output

I am going to sleep in timer 1
I waked in timer 1
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
I am going to sleep in timer 1
I waked in timer 1
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr

Here timer2 events queued until timer1 wake.

#####Scenario 2. Sleeping with loop.sleep

// Creating new event loop
SimpleEventLoop loop = new SimpleEventLoop();

// Starting. This will create a new thread.
loop.start();

// Creating a timer
SimpleTimer timer1 = loop.createTimer(new SimpleTimerCallback() {
	@Override
	public void onTimer(SimpleTimer timer) {
		System.out.println("I am going to sleep in timer 1");
		loop.sleep(5000);
		System.out.println("I waked in timer 1");
	}
});
timer1.start(10000);

// Creating another timer
SimpleTimer timer2 = loop.createTimer(new SimpleTimerCallback() {
	@Override
	public void onTimer(SimpleTimer timer) {
		System.out.println("Grrrrr");
	}
});
timer2.start(1000);

Output

I am going to sleep in timer 1
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
I waked in timer 1
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
I am going to sleep in timer 1
Grrrrr
Grrrrr
Grrrrr
Grrrrr
Grrrrr
I waked in timer 1

Here the timer2 events triggered while timer1 is sleeping.

###Network communication You can create a server client application easy using the event loop. #####Creating a server

SimpleEventLoop loop = new SimpleEventLoop();
loop.start();

Server server = loop.createServer(new ServerCallback() {
	@Override
	public void onData(Server server, Client client, Object message) {
		System.out.println("Data from client: " + client.getName() + " : " + message.toString());
		try {
			client.send("Hello Client");
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	@Override
	public void onDisconnected(Server server, Client client) {
		System.out.println("Client disconnected. " + client.getName());
	}

	@Override
	public void onConnect(Server server, Client client) {
		System.out.println("Connected new client. ");
		client.setName("Client1");
	}
});

try {
	server.start(3000);
} catch (IOException e) {
	e.printStackTrace();
}

#####Creating a client

SimpleEventLoop loop2 = new SimpleEventLoop();
loop2.start();

Client client = loop2.createClient(new ClientCallback() {
	@Override
	public void onData(Client client, Object message) {
		System.out.println("Data from server: " + message);
	}

	@Override
	public void onDisconnected(Client client) {
		System.out.println("Client disconnected");
	}

	@Override
	public void onConnect(Client client) {
		System.out.println("Client connected");
	}
});
try {
	client.connect("localhost", 3000);
	client.waitForConnect();
	client.send("Hello Server");
} catch (Exception e) {
	e.printStackTrace();
}

If you have any question feel free to contact me [e-mail]