chapters.mdc.NumberCruncherServer Maven / Gradle / Ivy

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/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package chapters.mdc;

import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
import java.util.Vector;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.MDC;

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.joran.JoranConfigurator;
import ch.qos.logback.core.joran.spi.JoranException;

/**
 * A simple NumberCruncher implementation that logs its progress when
 * factoring numbers. The purpose of the whole exercise is to show the
 * use of mapped diagnostic contexts in order to distinguish the log
 * output from different client requests.
 * */
public class NumberCruncherServer extends UnicastRemoteObject implements NumberCruncher {

    private static final long serialVersionUID = 1L;

    static Logger logger = LoggerFactory.getLogger(NumberCruncherServer.class);

    public NumberCruncherServer() throws RemoteException {
    }

    public int[] factor(int number) throws RemoteException {
        // The client's host is an important source of information.
        try {
            MDC.put("client", NumberCruncherServer.getClientHost());
        } catch (java.rmi.server.ServerNotActiveException e) {
            logger.warn("Caught unexpected ServerNotActiveException.", e);
        }

        // The information contained within the request is another source
        // of distinctive information. It might reveal the users name,
        // date of request, request ID etc. In servlet type environments,
        // useful information is contained in the HttpRequest or in the
        // HttpSession.
        MDC.put("number", String.valueOf(number));

        logger.info("Beginning to factor.");

        if (number <= 0) {
            throw new IllegalArgumentException(number + " is not a positive integer.");
        } else if (number == 1) {
            return new int[] { 1 };
        }

        Vector factors = new Vector();
        int n = number;

        for (int i = 2; (i <= n) && ((i * i) <= number); i++) {
            // It is bad practice to place log requests within tight loops.
            // It is done here to show interleaved log output from
            // different requests.
            logger.debug("Trying " + i + " as a factor.");

            if ((n % i) == 0) {
                logger.info("Found factor " + i);
                factors.addElement(i);

                do {
                    n /= i;
                } while ((n % i) == 0);
            }

            // Placing artificial delays in tight loops will also lead to
            // sub-optimal resuts. :-)
            delay(100);
        }

        if (n != 1) {
            logger.info("Found factor " + n);
            factors.addElement(n);
        }

        int len = factors.size();

        int[] result = new int[len];

        for (int i = 0; i < len; i++) {
            result[i] = ((Integer) factors.elementAt(i)).intValue();
        }

        // clean up
        MDC.remove("client");
        MDC.remove("number");

        return result;
    }

    static void usage(String msg) {
        System.err.println(msg);
        System.err.println("Usage: java chapters.mdc.NumberCruncherServer configFile\n" + "   where configFile is a logback configuration file.");
        System.exit(1);
    }

    public static void delay(int millis) {
        try {
            Thread.sleep(millis);
        } catch (InterruptedException e) {
        }
    }

    public static void main(String[] args) {
        if (args.length != 1) {
            usage("Wrong number of arguments.");
        }

        String configFile = args[0];

        if (configFile.endsWith(".xml")) {
            try {
                LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
                JoranConfigurator configurator = new JoranConfigurator();
                configurator.setContext(lc);
                lc.reset();
                configurator.doConfigure(args[0]);
            } catch (JoranException je) {
                je.printStackTrace();
            }
        }

        NumberCruncherServer ncs;

        try {
            ncs = new NumberCruncherServer();
            logger.info("Creating registry.");

            Registry registry = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);
            registry.rebind("Factor", ncs);
            logger.info("NumberCruncherServer bound and ready.");
        } catch (Exception e) {
            logger.error("Could not bind NumberCruncherServer.", e);

            return;
        }
    }
}