java 短链接生成

1. ?

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

   package shorurl; import org.apache.commons.codec.digest.DigestUtils; import org.apache.commons.lang.StringUtils; publicclassShortUrl{ privatestaticfinalint BINARY =0x2; privatestaticfinalint NUMBER_61 =0x0000003d; staticfinalchar[] DIGITS ={'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','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'}; protectedString shorten(String longUrl){ String shortUrl = shorten(longUrl,5); if(StringUtils.isEmpty(shortUrl)){ shortUrl = shorten(longUrl,6); } return shortUrl; } publicString shorten(String longUrl,int urlLength){ if(urlLength <0|| urlLength >6){ thrownewIllegalArgumentException("the length of url must be between 0 and 6"); } String md5Hex =DigestUtils.md5Hex(longUrl); // 6 digit binary can indicate 62 letter & number from 0-9a-zA-Z int binaryLength = urlLength *6; long binaryLengthFixer =Long.valueOf(StringUtils.repeat("1", binaryLength), BINARY); for(int i =0; i <4; i++){ String subString =StringUtils.substring(md5Hex, i *8,(i +1)*8); subString =Long.toBinaryString(Long.valueOf(subString,16)& binaryLengthFixer); subString =StringUtils.leftPad(subString, binaryLength,"0"); StringBuilder sbBuilder =newStringBuilder(); for(int j =0; j < urlLength; j++){ String subString2 =StringUtils.substring(subString, j *6,(j +1)*6); int charIndex =Integer.valueOf(subString2, BINARY)& NUMBER_61; sbBuilder.append(DIGITS[charIndex]); } String shortUrl = sbBuilder.toString(); return shortUrl; } returnnull; } }