GWT – UUID

marzo 2, 2012

Para identificar un elemento podemos utilizar un UUID. La ventaja de utilizar UUID’s es que los podemos crear tanto en el cliente como en el servidor. Al ser prácticamente únicos, las probabilidades de una colisión son mínimas.

En Java creas un nuevo UUID de la siguiente manera

import java.util.UUID;
String id=UUID.randomUUID().toString();

Pues en GWT no podemos utilizar esta clase porque no ha sido emulada( implementada ). Afortunadamente existe una implementación en Javascript que ha sido traducida a Java.

package de.hypergraphs.hyena.core.shared.data;

/**
File: Math.uuid.js
Version: 1.3
Change History:
  v1.0 - first release
  v1.1 - less code and 2x performance boost (by minimizing calls to Math.random())
  v1.2 - Add support for generating non-standard uuids of arbitrary length
  v1.3 - Fixed IE7 bug (can't use []'s to access string chars.  Thanks, Brian R.)
  v1.4 - Changed method to be "Math.uuid". Added support for radix argument.  Use module pattern for better encapsulation.

Latest version:   http://www.broofa.com/Tools/Math.uuid.js
Information:      http://www.broofa.com/blog/?p=151
Contact:          robert@broofa.com
----
Copyright (c) 2008, Robert Kieffer
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
    * Neither the name of Robert Kieffer nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

public class UUID {
	private static final char[] CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".toCharArray();
	/**
	 * Generate a random uuid of the specified length. Example: uuid(15) returns
	 * "VcydxgltxrVZSTV"
	 *
	 * @param len
	 *            the desired number of characters
	 */
	public static String uuid(int len) {
		return uuid(len, CHARS.length);
	}
	/**
	 * Generate a random uuid of the specified length, and radix. Examples:
*</pre>
<ul>*
	<li>uuid(8, 2) returns "01001010" (8 character ID, base=2)
*</li>
	<li>uuid(8, 10) returns "47473046" (8 character ID, base=10)
*</li>
	<li>uuid(8, 16) returns "098F4D35" (8 character ID, base=16)
 *</li>
</ul>
<pre>
	 *
	 * @param len
	 *            the desired number of characters
	 * @param radix
	 *            the number of allowable values for each character (must be  CHARS.length) {
			throw new IllegalArgumentException();
		}
		char[] uuid = new char[len];
		// Compact form
		for (int i = 0; i < len; i++) {
			uuid[i] = CHARS[(int)(Math.random()*radix)];
		}
		return new String(uuid);
	}
	/**
	 * Generate a RFC4122, version 4 ID. Example:
	 * "92329D39-6F5C-4520-ABFC-AAB64544E172"
	 */
	public static String uuid() {
		char[] uuid = new char[36];
		int r;

		// rfc4122 requires these characters
		uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
		uuid[14] = '4';

		// Fill in random data.  At i==19 set the high bits of clock sequence as
		// per rfc4122, sec. 4.1.5
		for (int i = 0; i < 36; i++) {
			if (uuid[i] == 0) {
				r = (int) (Math.random()*16);
				uuid[i] = CHARS[(i == 19) ? (r & 0x3) | 0x8 : r & 0xf];
			}
		}
		return new String(uuid);
	}
}

Fuentes:
http://www.2ality.com/2009/01/uuids-for-gwt.html
https://github.com/broofa/node-uuid

Responder

Introduce tus datos o haz clic en un icono para iniciar sesión:

Logo de WordPress.com

Estás comentando usando tu cuenta de WordPress.com. Cerrar sesión / Cambiar )

Imagen de Twitter

Estás comentando usando tu cuenta de Twitter. Cerrar sesión / Cambiar )

Foto de Facebook

Estás comentando usando tu cuenta de Facebook. Cerrar sesión / Cambiar )

Google+ photo

Estás comentando usando tu cuenta de Google+. Cerrar sesión / Cambiar )

Conectando a %s

A %d blogueros les gusta esto: