retrieve.java

一个对等计算发生器

/***************************************************************************
 *                                                                         *
 *                              Retrieve.java                              *
 *                            -------------------                          *
 *   date                 : 15.09.2004, 10:15                              *
 *   copyright            : (C) 2004/2005 Distributed and                  *
 *								Mobile Systems Group                       *
 *                              Lehrstuhl fuer Praktische Informatik       *
 *                              Universitaet Bamberg                       *
 *                              http://www.lspi.wiai.uni-bamberg.de/       *
 *   email                : [e-mail]              *
 *   						[e-mail]            *
 *                                                                         *
 *                                                                         *
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   A copy of the license can be found in the license.txt file supplied   *
 *   with this software or at: http://www.gnu.org/copyleft/gpl.html        *
 *                                                                         *
 ***************************************************************************/

package de.uniba.wiai.lspi.chord.console.command;

import java.io.Serializable;
import java.util.Set;

import de.uniba.wiai.lspi.chord.com.local.ChordImplAccess;
import de.uniba.wiai.lspi.chord.com.local.Registry;
import de.uniba.wiai.lspi.chord.com.local.ThreadEndpoint;
import de.uniba.wiai.lspi.chord.console.command.entry.Key;
import de.uniba.wiai.lspi.util.console.Command;
import de.uniba.wiai.lspi.util.console.ConsoleException;

/**
 * {@link Command} to retrieve a value from the local chord network.
 * 
 * To get a description of this command type <code>retrieve -help</code> into
 * the {@link de.uniba.wiai.lspi.chord.console.Main console}.
 * 
 * @author sven
 * @version 1.0.1
 */
public class Retrieve extends Command {

	/**
	 * The name of this {@link Command}.
	 */
	public static final String COMMAND_NAME = "retrieve";

	/**
	 * The name of the parameter, that defines the node from which the request
	 * to retrieve a value is made.
	 */
	protected static final String NODE_PARAM = "node";

	/**
	 * The name of the parameter, that defines the key of the value to be
	 * retrieved.
	 */
	protected static final String KEY_PARAM = "key";

	/** Creates a new instance of Retrieve 
	 * @param toCommand1 
	 * @param out11 */
	public Retrieve(Object[] toCommand1, java.io.PrintStream out11) {
		super(toCommand1, out11);
	}

	public void exec() throws ConsoleException {
		String node = this.parameters.get(NODE_PARAM);
		String key = this.parameters.get(KEY_PARAM);
		if ((node == null) || (node.length() == 0)) {
			throw new ConsoleException("Not enough parameters! " + NODE_PARAM
					+ " is missing.");
		}
		if ((key == null) || (key.length() == 0)) {
			throw new ConsoleException("Not enough parameters! " + KEY_PARAM
					+ " is missing.");
		}

		Key keyObject = new Key(key);

		ThreadEndpoint ep = Registry.getRegistryInstance().lookup(node);
		if (ep == null) {
			this.out.println("Node '" + node + "' does not exist!");
			return;
		}
		try {
			Set<Serializable> vs = ChordImplAccess.fetchChordImplOfNode(ep.getNode())
					.retrieve(keyObject);
			Object[] values = vs.toArray(new Object[vs.size()]);
			this.out.println("Values associated with key '" + key + "': ");
			for (int i = 0; i < values.length; i++) {
				this.out.print(values[i]);
				if (!(i == (values.length - 1))) {
					this.out.print(",");
				}
				this.out.print(" ");
			}
			this.out.println();
			this.out.println("Values retrieved from node '" + node + "'");
		} catch (Throwable t) {
			ConsoleException e = new ConsoleException(
					"Exception during execution of command. " + t.getMessage());
			e.setStackTrace(t.getStackTrace());
			throw e;
		}

	}

	public String getCommandName() {
		return COMMAND_NAME;
	}

	public void printOutHelp() {
		this.out
				.println("This command retrieves and displays the values stored for a provided key in the chord network.");
		this.out
				.println("The search is initiated by the node provided as parameter.");
		this.out.println("Required parameters: ");
		this.out.println("\t" + NODE_PARAM
				+ ": The name of the node, by that the search is initiated.");
		this.out.println("\t" + KEY_PARAM + ": The key for the values.");
		this.out.println();
	}

}