MD5加解密代碼



public final class MD5 {

 private MD5() {

 }

 /**
  * Used building output as Hex
  */
 private static final char[] DIGITS = { '0', '1', '2', '3', '4', '5', '6',
   '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

 /**
  * 根據content,key,按預定算法計算hash
  *
  * @param text
  * @param key
  * @return 加密結果
  */
 public static String hash(String text, String key) {
  if (text == null) {
   throw new IllegalArgumentException("text can't be null");
  }
  if (key == null) {
   throw new IllegalArgumentException("key can't be null");
  }
  try {
   String S = md5(key);
   byte[] textData = text.getBytes("UTF-8");
   int len = textData.length;
   int n = (len + 15) / 16;
   byte[] tempData = new byte[n * 16];
   for (int i = len; i < n * 16; i++) {
    tempData[i] = 0;
   }
   System.arraycopy(textData, 0, tempData, 0, len);
   textData = tempData;
   String[] c = new String[n];
   for (int i = 0; i < n; i++) {
    c[i] = new String(textData, 16 * i, 16,
      "UTF-8");
   }
   // end c
   String[] b = new String[n];
   String hash;

   // 2.計算b(i)
   // b(1)=MD5(S+c(1))
   // b(2)=MD5(b(1)+c(2))
   // ...
   // b(n)=MD5(b(n-1)+c(n))
   String temp = S;
   String target = "";
   for (int i = 0; i < n; i++) {
    b[i] = md5(temp + c[i]);
    temp = b[i];
    target += b[i];
   }

   // 3.hash=MD5(b(1)+b(2)+...+b(n))
   hash = md5(target);
   return hash;
  } catch (UnsupportedEncodingException e) {
   return null;
  }
 }

 /**
  * Converts an array of bytes into an array of characters representing the
  * hexidecimal values of each byte in order. The returned array will be
  * double the length of the passed array, as it takes two characters to
  * represent any given byte.
  *
  * @param data
  *            a byte[] to convert to Hex characters
  * @return A char[] containing hexidecimal characters
  */
 private static char[] encodeHex(byte[] data) {

  int l = data.length;

  char[] out = new char[l << 1];

  // two characters form the hex value.
  for (int i = 0, j = 0; i < l; i++) {
   out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
   out[j++] = DIGITS[0x0F & data[i]];
  }

  return out;
 }

 private static MessageDigest getMD5Digest() {
  try {
   MessageDigest md5MessageDigest = MessageDigest.getInstance("MD5");
   md5MessageDigest.reset();
   return md5MessageDigest;
  } catch (NoSuchAlgorithmException nsaex) {
   return null;
  }
 }

 /**
  * 計算content的md5摘要.
  *
  * @param content
  * @return md5結果
  */
 public static String md5(String content) {
  try {
   byte[] data = getMD5Digest().digest(
     content.getBytes("UTF-8"));
   char[] chars = encodeHex(data);
   return new String(chars);
  } catch (Exception ex) {
   return null;
  }
 }
 
 public static String md5UTF8(String content) {
  try {
   byte[] data = getMD5Digest().digest(
     content.getBytes("UTF-8"));
   char[] chars = encodeHex(data);
   return new String(chars);
  } catch (Exception ex) {
   return null;
  }
 }
 
 /**
  * 計算content的md5摘要.
  *
  * @param content
  * @return md5結果
  */
 public static String md5GBK(String content) {
  try {
   byte[] data = getMD5Digest().digest(
     content.getBytes("GBK"));
   char[] chars = encodeHex(data);
   return new String(chars);
  } catch (Exception ex) {
   return null;
  }
 }

 public static String getMd5ByFile(File file) {
  String value = null;
  FileInputStream in = null;
  try {
   in = new FileInputStream(file);
   MappedByteBuffer byteBuffer = in.getChannel().map(
     FileChannel.MapMode.READ_ONLY, 0, file.length());
   MessageDigest md5 = MessageDigest.getInstance("MD5");
   md5.update(byteBuffer);
   BigInteger bi = new BigInteger(1, md5.digest());
   value = bi.toString(16);
   while (value.length() < 32) {
    value = "0" + value;
   }
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   if (null != in) {
    try {
     in.close();
    } catch (IOException e) {
     e.printStackTrace();
    }
   }
  }
  return value;
 }
}