chapters.mdc.NumberCruncherServer Maven / Gradle / Ivy

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/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2011, 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;
    }
  }
}