책임 연쇄 패턴

1 개요

chain-of-responsibility pattern
역할 사슬 패턴

책임을 넘기는 구조
명령 객체와 일련의 처리 객체를 포함하는 디자인 패턴

2 예제 (java)

abstract class Logger {
    public static int ERR = 3;
    public static int NOTICE = 5;
    public static int DEBUG = 7;
    protected int mask;
 
    // The next element in the chain of responsibility
    protected Logger next;
 
    public Logger setNext(Logger log) {
        next = log;
        return log;
    }
 
    public void message(String msg, int priority) {
        if (priority <= mask) {
            writeMessage(msg);
        }
        if (next != null) {
            next.message(msg, priority);
        }
    }
 
    abstract protected void writeMessage(String msg);
}
 
class StdoutLogger extends Logger {
    public StdoutLogger(int mask) { 
        this.mask = mask;
    }
 
    protected void writeMessage(String msg) {
        System.out.println("Writing to stdout: " + msg);
    }
}
 
 
class EmailLogger extends Logger {
    public EmailLogger(int mask) {
        this.mask = mask;
    }
 
    protected void writeMessage(String msg) {
        System.out.println("Sending via email: " + msg);
    }
}
 
class StderrLogger extends Logger {
    public StderrLogger(int mask) {
        this.mask = mask;
    }
 
    protected void writeMessage(String msg) {
        System.err.println("Sending to stderr: " + msg);
    }
}
 
public class ChainOfResponsibilityExample {
    public static void main(String[] args) {
        // Build the chain of responsibility
        Logger logger, logger1;
        logger1 = logger = new StdoutLogger(Logger.DEBUG);
        logger1 = logger1.setNext(new EmailLogger(Logger.NOTICE));
        logger1 = logger1.setNext(new StderrLogger(Logger.ERR));
 
        // Handled by StdoutLogger
        logger.message("Entering function y.", Logger.DEBUG);
 
        // Handled by StdoutLogger and EmailLogger
        logger.message("Step1 completed.", Logger.NOTICE);
 
        // Handled by all three loggers
        logger.message("An error has occurred.", Logger.ERR);
    }
}

실행결과

  Writing to stdout:   Entering function y.
  Writing to stdout:   Step1 completed.
  Sending via e-mail:  Step1 completed.
  Writing to stdout:   An error has occurred.
  Sending via e-mail:  An error has occurred.
  Writing to stderr:   An error has occurred.

3 같이 보기

디자인 패턴

4 참고 자료

http://en.wikipedia.org/wiki/Chain-of-responsibility_pattern