Chain-of-responsibility pattern: Difference between revisions

Revision as of 23:59, 25 November 2006

Revision as of 08:48, 14 December 2006

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=== Java ===

The following Java code illustrates the pattern with the example of a logging class. Each logging handler decides if any action is to be taken at this log level and then passes the message on to the next logging handler. The output is:

Writing to debug output: Entering function xy.

Writing to debug output: Step1 completed.

Writing to stderr: Step1 completed.

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import java.util.*;

'''abstract class Logger''' {

public static int ERR = 3;

public static int NOTICE = 5;

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}

'''class DebugLogger ''extends Logger''''' {

public DebugLogger(int mask) { this.mask = mask; }

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}

'''class EMailLogger ''extends Logger''''' {

public EMailLogger(int mask) { this.mask = mask; }

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}

'''class StderrLogger ''extends Logger''''' {

public StderrLogger(int mask) { this.mask = mask; }

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}

'''class ChainOfResponsibilityExample''' {

public static void main(String[] args) {

// building the chain of responsibility

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new StderrLogger(Logger.NOTICE) ) );

l.message("Entering function xy.", Logger.DEBUG); ''// handled by DebugLogger''

l.message("Step1 completed.", Logger.NOTICE); ''// handled by Debug- and StderrLogger''

l.message("An error has occurred.", Logger.ERR); ''// handled by all three Logger''

}

}

==See also==