GWT customer. How do you get a unique ID?



  • The question is rather theoretical, in practice the System must be sufficient.currentTimeMillis();

    IP, pid browser, etc. I didn't find a way to get it from a client. (java, compiled in JS).



  • 1. As unique ID specially designed to do so UUID

    Since GWT http://code.google.com/intl/ru-RU/webtoolkit/doc/latest/RefJreEmulation.html On the client side, some alternative implementation should be used and maintained client-side:

    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:
         * <ul>
         * <li>uuid(8, 2) returns "01001010" (8 character ID, base=2)
         * <li>uuid(8, 10) returns "47473046" (8 character ID, base=10)
         * <li>uuid(8, 16) returns "098F4D35" (8 character ID, base=16)
         * </ul>
         * 
         * @param len
         *            the desired number of characters
         * @param radix
         *            the number of allowable values for each character (must be <=
         *            62)
         */
        public static String uuid(int len, int radix) {
            if (radix > 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 &lt; 36; i++) {
            if (uuid[i] == 0) {
                r = (int) (Math.random()*16);
                uuid[i] = CHARS[(i == 19) ? (r &amp; 0x3) | 0x8 : r &amp; 0xf];
            }
        }
        return new String(uuid);
    }
    

    }

    2. Client's IP.

    For information IP Customer has to be inherited from RemoteServiceServlet and use the method getThreadLocalRequest().getRemoteAddr()

    Do it. Total It is certainly not possible to have a clientele.

    3. Got it. PID Browser impossible, that is javascript without access PID in principle.

    For example, the type of browser can be easily obtained by means of a method JSNI:

     public static native String getUserAgent() /-{
    return navigator.userAgent.toLowerCase();
    }-
    /;


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