Java实现Base64加密解密

import java.io.ByteArrayOutputStream;

public class Base64
{
    private static char[] base64EncodeChars
= new char[] { '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', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

    private static byte[] base64DecodeChars
= new byte[] { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55,
            56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1
, 0, 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, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29
, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
            47, 48, 49, 50, 51, -1, -1, -1, -1, -1 };

    private Base64()
    {
    }

    public static String encode(byte[] data)
    {
        StringBuffer sb = new StringBuffer();
        int len = data.length;
        int i = 0;
        int b1, b2, b3;

        while (i < len)
        {
            b1 = data[i++] & 0xff;
            if (i == len)
            {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
                sb.append("==");
                break;
            }
            b2 = data[i++] & 0xff;
            if (i == len)
            {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
                sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
                sb.append("=");
                break;
            }
            b3 = data[i++] & 0xff;
            sb.append(base64EncodeChars[b1 >>> 2]);
            sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
            sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
            sb.append(base64EncodeChars[b3 & 0x3f]);
        }
        return sb.toString();
    }

    public static byte[] decode(String str)
    {
        byte[] data = str.getBytes();
        int len = data.length;
        ByteArrayOutputStream buf = new ByteArrayOutputStream(len);
        int i = 0;
        int b1, b2, b3, b4;

        while (i < len)
        {

            /* b1 */
            do
            {
                b1 = base64DecodeChars[data[i++]];
            }
            while (i < len && b1 == -1);
            if (b1 == -1)
            {
                break;
            }

            /* b2 */
            do
            {
                b2 = base64DecodeChars[data[i++]];
            }
            while (i < len && b2 == -1);
            if (b2 == -1)
            {
                break;
            }
            buf.write((int) ((b1 << 2) | ((b2 & 0x30) >>> 4)));

            /* b3 */
            do
            {
                b3 = data[i++];
                if (b3 == 61)
                {
                    return buf.toByteArray();
                }
                b3 = base64DecodeChars[b3];
            }
            while (i < len && b3 == -1);
            if (b3 == -1)
            {
                break;
            }
            buf.write((int) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));

            /* b4 */
            do
            {
                b4 = data[i++];
                if (b4 == 61)
                {
                    return buf.toByteArray();
                }
                b4 = base64DecodeChars[b4];
            }
            while (i < len && b4 == -1);
            if (b4 == -1)
            {
                break;
            }
            buf.write((int) (((b3 & 0x03) << 6) | b4));
        }
        return buf.toByteArray();
    }

    public static void main(String[] args)
    {
        Base64 base64 = new Base64();

        String testStr = "{\"name\":\"vicken\",\"age\":20}";
        System.out.println("加密前：" + testStr);

        String encodeStr = base64.encode(testStr.getBytes());
        System.out.println("加密数据：" + encodeStr);

        byte[] decodeStr = base64.decode(encodeStr);
        System.out.println("解密数据：" + new String(decodeStr));
    }
}