JAva暗号化Base 64暗号化

package org.hexun.wangchong.admin.filters;

public class SecBase64 {
private static final byte[] encodingTable = { (byte) 'A', (byte) 'B',
    (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
    (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L',
    (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q',
    (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V',
    (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a',
    (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
    (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k',
    (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
    (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
    (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
    (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4',
    (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
    (byte) '+', (byte) '/' };
private static final byte[] decodingTable;
static {
   decodingTable = new byte[128];
   for (int i = 0; i < 128; i++) {
    decodingTable[i] = (byte) -1;
   }
   for (int i = 'A'; i <= 'Z'; i++) {
    decodingTable[i] = (byte) (i - 'A');
   }
   for (int i = 'a'; i <= 'z'; i++) {
    decodingTable[i] = (byte) (i - 'a' + 26);
   }
   for (int i = '0'; i <= '9'; i++) {
    decodingTable[i] = (byte) (i - '0' + 52);
   }
   decodingTable['+'] = 62;
   decodingTable['/'] = 63;
}

/**
*   
* 
* @param data
* @return byte[]
*/
public static byte[] encode(byte[] data) {
   byte[] bytes;
   int modulus = data.length % 3;
   if (modulus == 0) {
    bytes = new byte[(4 * data.length) / 3];
   } else {
    bytes = new byte[4 * ((data.length / 3) + 1)];
   }
   int dataLength = (data.length - modulus);
   int a1;
   int a2;
   int a3;
   for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
    a1 = data[i] & 0xff;
    a2 = data[i + 1] & 0xff;
    a3 = data[i + 2] & 0xff;
    bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
    bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
    bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
    bytes[j + 3] = encodingTable[a3 & 0x3f];
   }
   int b1;
   int b2;
   int b3;
   int d1;
   int d2;
   switch (modulus) {
   case 0: /* nothing left to do */
    break;
   case 1:
    d1 = data[data.length - 1] & 0xff;
    b1 = (d1 >>> 2) & 0x3f;
    b2 = (d1 << 4) & 0x3f;
    bytes[bytes.length - 4] = encodingTable[b1];
    bytes[bytes.length - 3] = encodingTable[b2];
    bytes[bytes.length - 2] = (byte) '=';
    bytes[bytes.length - 1] = (byte) '=';
    break;
   case 2:
    d1 = data[data.length - 2] & 0xff;
    d2 = data[data.length - 1] & 0xff;
    b1 = (d1 >>> 2) & 0x3f;
    b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
    b3 = (d2 << 2) & 0x3f;
    bytes[bytes.length - 4] = encodingTable[b1];
    bytes[bytes.length - 3] = encodingTable[b2];
    bytes[bytes.length - 2] = encodingTable[b3];
    bytes[bytes.length - 1] = (byte) '=';
    break;
   }
   return bytes;
}

/**
*   
* 
* @param data
* @return byte[]
*/
public static byte[] decode(byte[] data) {
   byte[] bytes;
   byte b1;
   byte b2;
   byte b3;
   byte b4;
   data = discardNonBase64Bytes(data);
   if (data[data.length - 2] == '=') {
    bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
   } else if (data[data.length - 1] == '=') {
    bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
   } else {
    bytes = new byte[((data.length / 4) * 3)];
   }
   for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) {
    b1 = decodingTable[data[i]];
    b2 = decodingTable[data[i + 1]];
    b3 = decodingTable[data[i + 2]];
    b4 = decodingTable[data[i + 3]];
    bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
    bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
    bytes[j + 2] = (byte) ((b3 << 6) | b4);
   }
   if (data[data.length - 2] == '=') {
    b1 = decodingTable[data[data.length - 4]];
    b2 = decodingTable[data[data.length - 3]];
    bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
   } else if (data[data.length - 1] == '=') {
    b1 = decodingTable[data[data.length - 4]];
    b2 = decodingTable[data[data.length - 3]];
    b3 = decodingTable[data[data.length - 2]];
    bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
    bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
   } else {
    b1 = decodingTable[data[data.length - 4]];
    b2 = decodingTable[data[data.length - 3]];
    b3 = decodingTable[data[data.length - 2]];
    b4 = decodingTable[data[data.length - 1]];
    bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
    bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
    bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
   }
   return bytes;
}

/**
*   
* 
* @param data
* @return byte[]
*/
public static byte[] decode(String data) {
   byte[] bytes;
   byte b1;
   byte b2;
   byte b3;
   byte b4;
   data = discardNonBase64Chars(data);
   if (data.charAt(data.length() - 2) == '=') {
    bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
   } else if (data.charAt(data.length() - 1) == '=') {
    bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
   } else {
    bytes = new byte[((data.length() / 4) * 3)];
   }
   for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) {
    b1 = decodingTable[data.charAt(i)];
    b2 = decodingTable[data.charAt(i + 1)];
    b3 = decodingTable[data.charAt(i + 2)];
    b4 = decodingTable[data.charAt(i + 3)];
    bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
    bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
    bytes[j + 2] = (byte) ((b3 << 6) | b4);
   }
   if (data.charAt(data.length() - 2) == '=') {
    b1 = decodingTable[data.charAt(data.length() - 4)];
    b2 = decodingTable[data.charAt(data.length() - 3)];
    bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
   } else if (data.charAt(data.length() - 1) == '=') {
    b1 = decodingTable[data.charAt(data.length() - 4)];
    b2 = decodingTable[data.charAt(data.length() - 3)];
    b3 = decodingTable[data.charAt(data.length() - 2)];
    bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
    bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
   } else {
    b1 = decodingTable[data.charAt(data.length() - 4)];
    b2 = decodingTable[data.charAt(data.length() - 3)];
    b3 = decodingTable[data.charAt(data.length() - 2)];
    b4 = decodingTable[data.charAt(data.length() - 1)];
    bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
    bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
    bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
   }
   return bytes;
}

private static byte[] discardNonBase64Bytes(byte[] data) {
   byte[] temp = new byte[data.length];
   int bytesCopied = 0;
   for (int i = 0; i < data.length; i++) {
    if (isValidBase64Byte(data[i])) {
     temp[bytesCopied++] = data[i];
    }
   }
   byte[] newData = new byte[bytesCopied];
   System.arraycopy(temp, 0, newData, 0, bytesCopied);
   return newData;
}

private static String discardNonBase64Chars(String data) {
   StringBuffer sb = new StringBuffer();
   int length = data.length();
   for (int i = 0; i < length; i++) {
    if (isValidBase64Byte((byte) (data.charAt(i)))) {
     sb.append(data.charAt(i));
    }
   }
   return sb.toString();
}

private static boolean isValidBase64Byte(byte b) {
   if (b == '=') {
    return true;
   } else if ((b < 0) || (b >= 128)) {
    return false;
   } else if (decodingTable[b] == -1) {
    return false;
   }
   return true;
}

// MjU5MjAwMA==
/**
*    
*/
public static void main(String[] args) {
   String data = "   ";
   byte[] result = SecBase64.encode(data.getBytes());//   
   System.out.println(data);
   System.out.println(new String(result));
   System.out.println(new String(SecBase64.decode(new String(result))));//   
   }
}