Behavioral Patterns : Chain of Responsibilities

Properties:

-          Lets a request to be passed sequentially to a set of handlers.

-          Each handler decides wheter to handle the request or pass it to next handler.

Implementation:

-          Handler interface declares operations to handle requests.

-          ConcreteHandler decides wheter to handle the request or pass it to next handler.

Java Standard Library Implementations:

-          javax.servlet.Filter#doFilter(ServletRequest request,ServletResponse response,FilterChain chain)

-          java.util.logging.Logger#log(Level,String)

Example Usage:

public class Logger {

    public void log(LogRecord paramLogRecord){

        Logger localLogger = this;

        while (localLogger != null) {

            // send log record to all handlers

            for (Handler localHandler : localLogger.getHandlers()) {

                localHandler.publish(paramLogRecord);

            }

            if (!localLogger.getUseParentHandlers())

            {

                break;

            }

            localLogger = localLogger.getParent();

        }

    }

   

    ....

}