MINA(1)Chain and Observer Basic Theory

MINA(1)Chain and Observer Basic Theory

Before, I just demo the MINA and use spring to integrate the MINA in my web application.

I learn MINA from others' blog, start from the basic design ideas.

1. Chain of filters, or rather say, handlers
One simple example for chain
Object iphone
package com.sillycat.easynio.plugins.mina.chain;

public class Iphone {

private String state = "IOS mobile phone!";

public String getState() {
return state;
}

public void setState(String state) {
this.state = state;
}
}

Interface for Workers
package com.sillycat.easynio.plugins.mina.chain;

public interface IWorker {

public void handle(Iphone iphone);

public void setNextWorker(IWorker worker);
}

One implementation of workers based on the interface
package com.sillycat.easynio.plugins.mina.chain;

public class WorkerDevice implements IWorker {

private IWorker next;

public void handle(Iphone iphone) {
iphone.setState(iphone.getState() + " Hardware Device is OK - ");
if (next != null) {
next.handle(iphone);
}
}

public void setNextWorker(IWorker worker) {
this.next = worker;
}

}

The factory will arrange all the workers to work together:
package com.sillycat.easynio.plugins.mina.chain;

public class IphoneFactory {

public static void main(String[] args) {

IWorker worker1 = new WorkerDevice();  
IWorker worker2 = new WorkerSoftware();  
IWorker worker3 = new WorkerIntegration();  
 
worker1.setNextWorker(worker2);  
worker2.setNextWorker(worker3);  

Iphone iphone = new Iphone();  
worker1.handle(iphone);  
System.out.println(iphone.getState()); 
}

}

How is chain used in MINA

IoFilterAdapter -----> IoFilter ---- NextFilter
                              Entry
                              EntryImpl

DefaultIoFiterChain

2. Watch and Observe
Observer and Subject, once the subject is changed, it will send event to observers.

class --------> java.util.Observer
interface---> java.util.Observable

Oberver means that the class is a observer. Observable means that the class is a subject. Other observers can observe it.

There is an exmaple for Heater, Display and Alarm.
package com.sillycat.easynio.plugins.mina.observer;

import java.util.Observable;

public class Heater extends Observable {

private int temperature;

public int getTemperature() {
return temperature;
}

public void setTemperature(int temperature) {
this.temperature = temperature;
}

public void boilWater() {
for (int i = 90; i < 100; i++) {
temperature = i;
this.setChanged();
this.notifyObservers(i);
}
}
}

package com.sillycat.easynio.plugins.mina.observer;

import java.util.Observable;
import java.util.Observer;

public class Display extends Observable implements Observer {

private String status = "Not yet!";

public void setStatus(String status) {
this.status = status;
}

public void displayTemputer(int temperature) {
System.out.println("Status: " + status + " Temprature: " + temperature
+ "");
if (temperature > 95) {
this.setStatus("Boiled!");
this.setChanged();
this.notifyObservers();
}
}

public void update(Observable o, Object arg) {
System.out.print( "num is i = " + arg + " ");
displayTemputer(((Heater) o).getTemperature());
}

}

package com.sillycat.easynio.plugins.mina.observer;

import java.util.Observable;
import java.util.Observer;

public class Alarm implements Observer {

public void makeAlarm() {
System.out.println("Alarm, alarm, the water is boiled! ");
}

public void update(Observable o, Object arg) {
makeAlarm();
}

}

package com.sillycat.easynio.plugins.mina.observer;

public class AlarmTest {

public static void main(String[] args) {
Heater header = new Heater();
Display display = new Display();
Alarm alarm = new Alarm();

header.addObserver(display);
display.addObserver(alarm);
header.boilWater();
}
}

Here is another interesting example about sexy girl, color wolf and sage.
package com.sillycat.easynio.plugins.mina.observer;

import java.util.Observable;

public class SexyGirl extends Observable {

private String state = "With All Clothes!";

public String getState() {
return state;
}

public void setState(String state) {
this.state = state;
}

public void dance() {
this.state = " Without all Clothes!";
this.setChanged();
this.notifyObservers();
}

}

package com.sillycat.easynio.plugins.mina.observer;

import java.util.Observable;
import java.util.Observer;

public class ColorWolf implements Observer {

public void update(Observable o, Object arg) {
SexyGirl subject = (SexyGirl)o;
if(subject != null){
System.out.println("Oh, I am color wolf, I see.");
}
}
}

package com.sillycat.easynio.plugins.mina.observer;

import java.util.Observable;
import java.util.Observer;

public class Sage implements Observer {

public void update(Observable o, Object arg) {
SexyGirl subject = (SexyGirl) o;
if (subject != null) {
System.out.println("I am sage, sexy is empty to me!");
}
}

}

package com.sillycat.easynio.plugins.mina.observer;

public class WolfTest {


public static void main(String[] args) {
SexyGirl girl = new SexyGirl();
ColorWolf wolf = new ColorWolf();
Sage sage = new Sage();

girl.addObserver(wolf);
girl.addObserver(sage);
girl.dance();
}
}

From observer to Event
In JDK,
java.util.EventListener
java.util.EventObject

In MINA,
IoServiceListener watch the service and session creating, idle and destroying.
IoFutureListener watch the IoFuture.

references:
http://sillycat.iteye.com/blog/563764
http://sillycat.iteye.com/blog/563765

http://www.iteye.com/topic/1124504
http://www.iteye.com/topic/1124605
http://www.iteye.com/topic/1124736
http://www.iteye.com/topic/1125178

http://kantery.iteye.com/blog/338715