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binjoo/ShortUrl.java

Created November 16, 2012 04:51
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  1. binjoo renamed this gist Apr 23, 2014. 1 changed file with 0 additions and 0 deletions.
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  3. binjoo created this gist Nov 16, 2012.
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    import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;

    /**
    * 【转】URL短地址压缩算法 微博短地址原理解析
    * http://www.cnblogs.com/jinzhao/archive/2012/04/08/2437188.html
    *
    */
    public class ShortUrl {
    public static String[] generateCode(String url) {
    String key = "Binjoo"; // 网址的混合KEY
    String[] chars = { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j",
    "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v",
    "w", "x", "y", "z", "0", "1", "2", "3", "4", "5", "6", "7",
    "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J",
    "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
    "W", "X", "Y", "Z" };
    String hex = toMd5(key + url);// 对传入网址和混合KEY进行MD5加密
    String[] resUrl = new String[4];

    for (int i = 0; i < 4; i++) {
    // 把加密字符按照8位一组16进制与0x3FFFFFFF进行位与运算
    String sTempSubString = hex.substring(i * 8, i * 8 + 8);
    long lHexLong = 0x3FFFFFFF & Long.parseLong(sTempSubString, 16);
    String outChars = "";
    for (int j = 0; j < 6; j++) {
    // 把得到的值与 0x0000003D 进行位与运算，取得字符数组 chars 索引
    long index = 0x0000003D & lHexLong;
    // 把取得的字符相加
    outChars += chars[(int) index];
    // 每次循环按位右移 5 位
    lHexLong = lHexLong >> 5;
    }
    resUrl[i] = outChars;
    }

    return resUrl;
    }

    private static String toMd5(String arg) {
    try {
    MessageDigest md = MessageDigest.getInstance("MD5");
    md.update(arg.getBytes());
    byte b[] = md.digest();
    int i;
    StringBuffer buf = new StringBuffer("");
    for (int offset = 0; offset < b.length; offset++) {
    i = b[offset];
    if (i < 0)
    i += 256;
    if (i < 16)
    buf.append("0");
    buf.append(Integer.toHexString(i));
    }
    return buf.toString();
    } catch (NoSuchAlgorithmException e) {
    e.printStackTrace();
    }
    return "";
    }
    }