入参：encryptedData，IV，sessionKeyCipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
   sun.misc.BASE64Decoder base64Decoder = new sun.misc.BASE64Decoder();
   byte[] _encryptedData = base64Decoder.decodeBuffer(encryptedData);
   byte[] _sessionKey = base64Decoder.decodeBuffer(sessionKey);
   byte[] _iv = base64Decoder.decodeBuffer(iv);
   SecretKeySpec secretKeySpec = new SecretKeySpec(_sessionKey, "AES");
   IvParameterSpec ivParameterSpec = new IvParameterSpec(_iv);
   cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
   byte[] original = cipher.doFinal(_encryptedData);
   PKCS7Encoder pk = new PKCS7Encoder();
   byte[] bytes = pk.decode(original);

   String originalString = new String(bytes, "utf-8");
   System.out.println("originalString1="+originalString);

这是解码的代码，基本上第二次，就会出现乱码,怎么解决？