java Base64算法的使用

　　Base64是常见的网络加密算法，Base64编码可用于在HTTP环境下传递较长的标识信息。详见 Base64介绍

1 自定义的base64算法

Base64Encrypt.java

public class Base64Encrypt {
    private static final String CODES = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    // base64解密
    private static byte[] base64Decode(String input) {
        if (input.length() %  != ) {
            throw new IllegalArgumentException("Invalid base64 input");
        }
        byte decoded[] = new byte[((input.length() * ) / )
                - (input.indexOf('=') >  ? (input.length() - input.indexOf('=')) : )];
        char[] inChars = input.toCharArray();
        int j = ;
        int b[] = new int[];
        for (int i = ; i < inChars.length; i += ) {
            // This could be made faster (but more complicated) by precomputing
            // these index locations.
            b[] = CODES.indexOf(inChars[i]);
            b[] = CODES.indexOf(inChars[i + ]);
            b[] = CODES.indexOf(inChars[i + ]);
            b[] = CODES.indexOf(inChars[i + ]);
            decoded[j++] = (byte) ((b[] << ) | (b[] >> ));
            if (b[] < ) {
                decoded[j++] = (byte) ((b[] << ) | (b[] >> ));
                if (b[] < ) {
                    decoded[j++] = (byte) ((b[] << ) | b[]);
                }
            }
        }
        return decoded;
    }

    // base64加密
    private static String base64Encode(byte[] in) {
        StringBuilder out = new StringBuilder((in.length * ) / );
        int b;
        for (int i = ; i < in.length; i += ) {
            b = (in[i] & 0xFC) >> ;
            out.append(CODES.charAt(b));
            b = (in[i] & 0x03) << ;
            if (i +  < in.length) {
                b |= (in[i + ] & 0xF0) >> ;
                out.append(CODES.charAt(b));
                b = (in[i + ] & 0x0F) << ;
                if (i +  < in.length) {
                    b |= (in[i + ] & 0xC0) >> ;
                    out.append(CODES.charAt(b));
                    b = in[i + ] & 0x3F;
                    out.append(CODES.charAt(b));
                } else {
                    out.append(CODES.charAt(b));
                    out.append('=');
                }
            } else {
                out.append(CODES.charAt(b));
                out.append("==");
            }
        }
        return out.toString();
    }

测试代码：

    public static void main(String[] args) {
        String input = "we are a team.";
        String encode = base64Encode(input.getBytes());
        System.out.println("encode: " + encode);

        String decode = new String(base64Decode(encode));
        System.out.println("decode: " + decode);
    }

2 bcprov的Base64算法

　　引入bcprov-jdk15on-154.jar，提供对base64算法的支持

bcprov-jdk15on-154.jar地址：　https://commons.apache.org/proper/commons-codec/download_codec.cgi

　　测试代码：

String input ="we are a team .";
 byte[] encodeBytes = org.bouncycastle.util.encoders.Base64.encode(input.getBytes());
    System.out.println("encode: " + new String(encodeBytes));

    byte[] decodeBytes = org.bouncycastle.util.encoders.Base64.decode(encodeBytes);
    System.out.println("decode: " + new String(decodeBytes));