Base64工具类

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package com.fly.util.Base64;/** * @Title: Base64工具类 * @ClassName: com.newcapec.util.Base64.Base64.java * @Description: * * @author: FLY * @date:  2017-10-18 17:10 * @version V1.0 */public class Base64 {    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;    }    /**     * @Title: 编码     * @methodName:  encode     * @param data【byte[]】     * @param offset 【int】     * @return byte[]     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:11     */    public static byte[] encode(byte[] data, int offset) {        byte[] bytes;        int realCount = data.length - offset;        int modulus = realCount % 3;        if (modulus == 0) {            bytes = new byte[(4 * realCount) / 3];        } else {            bytes = new byte[4 * ((realCount / 3) + 1)];        }        int dataLength = (data.length - modulus);        int a1;        int a2;        int a3;        for (int i = offset, 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;    }    /**     * @Title: 解码     * @methodName:  decode     * @param data 【byte[]】     * @return byte[]     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:12     */    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;    }    /**     * @Title: 解码     * @methodName:  decode     * @param data 【String】     * @return byte[]     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:13     */    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);        }        for (int i = 0; i < bytes.length; i++) {            System.out.println("," + bytes[i]);        }        return bytes;    }    /**     * @Title: 摒弃非Base64的字节     * @methodName:  discardNonBase64Bytes     * @param data     * @return byte[]     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:15     */    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;    }    /**     * @Title: 摒弃非Base64的字符     * @methodName:  discardNonBase64Chars     * @param data     * @return java.lang.String     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:19     */    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();    }    /**     * @Title: Base64Byte校验     * @methodName:  isValidBase64Byte     * @param b     * @return boolean     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:17     */    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;    }    /**     * @Title: 编码     * @methodName:  encode     * @param data     * @param charset 字符集     * @return java.lang.String     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:16     */    public static String encode(String data, String charset) throws Exception {        // byte[] result = (data.getBytes("Unicode"));        if (data == null || data.length() == 0) {            return data;        }        int offset = 0;        // getBytes("unicode")转完后会在前头加上两字节”FE“        byte[] result = encode(data.getBytes(charset), offset);        StringBuffer sb = new StringBuffer(result.length);        for (int i = 0; i < result.length; i++) {            sb.append((char) result[i]);        }        return sb.toString();    }    /**     * @Title:  解码     * @methodName:  decode     * @param data     * @param charset 字符集     * @return java.lang.String     * @Description:     *     * @author: FLY     * @date:  2017-10-18 17:15     */    public static String decode(String data, String charset) throws Exception {        if (data == null || data.length() == 0) {            return data;        }        return new String(Base64.decode(data), charset);    }    public static void main(String[] args) throws Exception {        String data = "我们";        String data1 = encode(data, "Unicode");        String data2 = decode(data1, "Unicode");        System.out.println(data);        System.out.println(data1);        System.out.println(data2);    }}
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