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;

   }