= Chain of responsibility Pattern =
각 요구를 처리할 수 있는지, 없는지를 순서대로 검색해가며 책임 떠넘기기. 복수의 객체가 연결되어 있는 내부의 어딘가에서 처리 수행. "어떤 처리를 어떤 객체가 수행해야 한다"는 정보를 중앙집권적으로 갖는게 아니라 각 객체에게 떠넘기기.

{{tag>Architecture Modeling Design_Pattern Behavioral}}

= Handler =
<sxh java ; title:처리해야 할 일 ; collapse:true>
public class Trouble {
	private int number;

	public Trouble(int number) {
		super();
		this.number = number;
	}

	public int getNumber() {
		return number;
	}

	@Override
	public String toString() {
		return "Trouble [number=" + number + "]";
	}
}
</sxh>

<sxh java ; title:Handler ; highlight:[9-12,23]>
public abstract class Support {
	private String name;
	private Support next;
	
	public Support(String name) {
		this.name = name;
	}

	public Support setNext(Support next) {
		this.next = next;
		return next;
	}
	
	public final void support(Trouble trouble) {
		if(resolve(trouble))
			done(trouble);
		else if(next != null)
			next.support(trouble);
		else
			fail(trouble);
	}
	
	protected abstract boolean resolve(Trouble trouble);
	
	protected void done(Trouble trouble) {
		System.out.println(trouble + " is resolved by " + this);
	}
	
	protected void fail(Trouble trouble) {
		System.out.println(trouble + " cannot be resolved.");
	}

	@Override
	public String toString() {
		return "[" + name + "]";
	}
}
</sxh>

<sxh java ; title:ConcreteHandler>
public class NoSupport extends Support {

	public NoSupport(String name) {
		super(name);
	}

	@Override
	protected boolean resolve(Trouble trouble) {
		return false;
	}
}
</sxh>

<sxh java ; title:ConcreteHandler>
public class LimitSupport extends Support {

	private int limit;
	
	public LimitSupport(String name, int limit) {
		super(name);
		this.limit = limit;
	}

	@Override
	protected boolean resolve(Trouble trouble) {
		return trouble.getNumber() < limit;
	}
}
</sxh>

<sxh java ; title:ConcreteHandler>
public class SpecialSupport extends Support {

	private int number;
	
	public SpecialSupport(String name, int number) {
		super(name);
		this.number = number;
	}

	@Override
	protected boolean resolve(Trouble trouble) {
		return trouble.getNumber() % 2 == number;
	}

}
</sxh>

<sxh java ; title:ConcreteHandler>
public class OddSupport extends Support {

	public OddSupport(String name) {
		super(name);
	}

	@Override
	protected boolean resolve(Trouble trouble) {
		return trouble.getNumber() % 2 == 1;
	}

}
</sxh>


= Client =
<sxh java ; highlight:[11,15]>
public class Client {
    public static void main(String[] args) {
    	Support alice = new NoSupport("Alice");
    	Support bob = new LimitSupport("Bob", 100);
    	Support charlie = new SpecialSupport("Charlie", 429);
    	Support diana = new LimitSupport("Diana", 200);
    	Support elmo = new OddSupport("Elmo");
    	Support fred = new LimitSupport("Fred", 300);
    	
        // Build the chain of responsibility
    	alice.setNext(bob).setNext(charlie).setNext(diana).setNext(elmo).setNext(fred);
    	
    	// Handled by Handlers
    	for(int i=0 ; i<500 ; i+=33) {
    		alice.support(new Trouble(i));
    	}
    }
}


/*
Trouble [number=0] is resolved by [Bob]
Trouble [number=33] is resolved by [Bob]
Trouble [number=66] is resolved by [Bob]
Trouble [number=99] is resolved by [Bob]
Trouble [number=132] is resolved by [Diana]
Trouble [number=165] is resolved by [Diana]
Trouble [number=198] is resolved by [Diana]
Trouble [number=231] is resolved by [Elmo]
Trouble [number=264] is resolved by [Fred]
Trouble [number=297] is resolved by [Elmo]
Trouble [number=330] cannot be resolved.
Trouble [number=363] is resolved by [Elmo]
Trouble [number=396] cannot be resolved.
Trouble [number=429] is resolved by [Elmo]
Trouble [number=462] cannot be resolved.
Trouble [number=495] is resolved by [Elmo]
*/
</sxh>