package com.john.j2se.util;     
/**    
 * MD5加密算法 ,是一种单向加密算法。  
 */    
import java.security.MessageDigest;     
    
public class MD5Util {     
    public final static String MD5(String s) {     
        char hexDigits[] = { '0', '1', '2', '3', '4',     
                             '5', '6', '7', '8', '9',     
                             'A', 'B', 'C', 'D', 'E', 'F'};     
        try {     
            byte[] btInput = s.getBytes();     
            MessageDigest mdInst = MessageDigest.getInstance("MD5");     
            mdInst.update(btInput);     
            byte[] md = mdInst.digest();     
            int j = md.length;     
            char str[] = new char[j * 2];     
            int k = 0;     
            for (int i = 0; i < j; i++) {     
                byte byte0 = md[i];     
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];     
                str[k++] = hexDigits[byte0 & 0xf];     
            }     
            return new String(str);     
        }     
        catch (Exception e) {     
            e.printStackTrace();     
            return null;     
        }     
    }     
} 


/**
 * Base64 是一种双向加密算法
 */
import java.io.UnsupportedEncodingException;    
  
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 };

  //编码     
    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();     
    }     
    //解码     
    public static byte[] decode(String str) throws UnsupportedEncodingException {     
        StringBuffer sb = new StringBuffer();     
        byte[] data = str.getBytes("US-ASCII");     
        int len = data.length;     
        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;    
            sb.append((char)((b1 << 2) | ((b2 & 0x30) >>> 4)));    
            /* b3 */   
            do {    
                b3 = data[i++];    
                if (b3 == 61) return sb.toString().getBytes("iso8859-1");    
                b3 = base64DecodeChars[b3];    
            } while (i < len && b3 == -1);    
            if (b3 == -1) break;    
            sb.append((char)(((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));    
            /* b4 */   
            do {    
                b4 = data[i++];    
                if (b4 == 61) return sb.toString().getBytes("iso8859-1");    
                b4 = base64DecodeChars[b4];    
            } while (i < len && b4 == -1);    
            if (b4 == -1) break;    
            sb.append((char)(((b3 & 0x03) << 6) | b4));    
        }    
        return sb.toString().getBytes("iso8859-1");    
    }    
}