一、反射
/*** 
     * encode by Base64 
     */  
    public static String encodeBase64(byte[]input) throws Exception{  
        Class clazz=Class.forName("com.sun.org.apache.xerces.internal.impl.dv.util.Base64");  
        Method mainMethod= clazz.getMethod("encode", byte[].class);  
        mainMethod.setAccessible(true);  
         Object retObj=mainMethod.invoke(null, new Object[]{input});  
         return (String)retObj;  
    }  
    /*** 
     * decode by Base64 
     */  
    public static byte[] decodeBase64(String input) throws Exception{  
        Class clazz=Class.forName("com.sun.org.apache.xerces.internal.impl.dv.util.Base64");  
        Method mainMethod= clazz.getMethod("decode", String.class);  
        mainMethod.setAccessible(true);  
         Object retObj=mainMethod.invoke(null, input);  
         return (byte[])retObj;  
    }

  二、使用commons-codec.jar
  /** 
         * @param bytes 
         * @return 
         */  
        public static byte[] decode(final byte[] bytes) {  
            return Base64.decodeBase64(bytes);  
        }  
      
        /** 
         * 二进制数据编码为BASE64字符串 
         * 
         * @param bytes 
         * @return 
         * @throws Exception 
         */  
        public static String encode(final byte[] bytes) {  
            return new String(Base64.encodeBase64(bytes));  
        }  

三、
/**  
    * 编码  
    * @param bstr  
    * @return String  
    */    
   public static String encode(byte[] bstr){    
   return new sun.misc.BASE64Encoder().encode(bstr);    
   }    
   
   /**  
    * 解码  
    * @param str  
    * @return string  
    */    
   public static byte[] decode(String str){    
   byte[] bt = null;    
   try {    
       sun.misc.BASE64Decoder decoder = new sun.misc.BASE64Decoder();    
       bt = decoder.decodeBuffer( str );    
   } catch (IOException e) {    
       e.printStackTrace();    
   }    
   
       return bt;    
   }