一 Base64加密

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.OutputStream;

public class Base64Utils {

    private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

    /**

     * data[]进行编码

     *

     * @param data

     * @return

     */

    public static String encode(byte[] data) {

        int start = 0;

        int len = data.length;

        StringBuffer buf = new StringBuffer(data.length * 3 / 2);

        int end = len - 3;

        int i = start;

        int n = 0;

        while (i <= end) {

            int d = ((((int) data[i]) & 0x0ff) << 16)

                    | ((((int) data[i + 1]) & 0x0ff) << 8)

                    | (((int) data[i + 2]) & 0x0ff);

            buf.append(legalChars[(d >> 18) & 63]);

            buf.append(legalChars[(d >> 12) & 63]);

            buf.append(legalChars[(d >> 6) & 63]);

            buf.append(legalChars[d & 63]);

            i += 3;

            if (n++ >= 14) {

                n = 0;

                buf.append(" ");

            }

        }

        if (i == start + len - 2) {

            int d = ((((int) data[i]) & 0x0ff) << 16)

                    | ((((int) data[i + 1]) & 255) << 8);

            buf.append(legalChars[(d >> 18) & 63]);

            buf.append(legalChars[(d >> 12) & 63]);

            buf.append(legalChars[(d >> 6) & 63]);

            buf.append("=");

        } else if (i == start + len - 1) {

            int d = (((int) data[i]) & 0x0ff) << 16;

            buf.append(legalChars[(d >> 18) & 63]);

            buf.append(legalChars[(d >> 12) & 63]);

            buf.append("==");

        }

        return buf.toString();

    }

    private static int decode(char c) {

        if (c >= 'A' && c <= 'Z')

            return ((int) c) - 65;

        else if (c >= 'a' && c <= 'z')

            return ((int) c) - 97 + 26;

        else if (c >= '0' && c <= '9')

            return ((int) c) - 48 + 26 + 26;

        else

            switch (c) {

                case '+':

                    return 62;

                case '/':

                    return 63;

                case '=':

                    return 0;

                default:

                    throw new RuntimeException("unexpected code: " + c);

            }

    }

    /**

     * Decodes the given Base64 encoded String to a new byte array. The byte

     * array holding the decoded data is returned.

     */

    public static byte[] decode(String s) {

        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        try {

            decode(s, bos);

        } catch (IOException e) {

            throw new RuntimeException();

        }

        byte[] decodedBytes = bos.toByteArray();

        try {

            bos.close();

            bos = null;

        } catch (IOException ex) {

            System.err.println("Error while decoding BASE64: " + ex.toString());

        }

        return decodedBytes;

    }

    private static void decode(String s, OutputStream os) throws IOException {

        int i = 0;

        int len = s.length();

        while (true) {

            while (i < len && s.charAt(i) <= ' ')

                i++;

            if (i == len)

                break;

            int tri = (decode(s.charAt(i)) << 18)

                    + (decode(s.charAt(i + 1)) << 12)

                    + (decode(s.charAt(i + 2)) << 6)

                    + (decode(s.charAt(i + 3)));

            os.write((tri >> 16) & 255);

            if (s.charAt(i + 2) == '=')

                break;

            os.write((tri >> 8) & 255);

            if (s.charAt(i + 3) == '=')

                break;

            os.write(tri & 255);

            i += 4;

        }

    }

}