我正在编写使用aes的服务器/客户机系统。以下方法（服务器端）工作正常：

public static byte[] encode(byte type, byte subType, String string, Cipher cipher) 
    throws NullPointerException, IOException {

        Objects.requireNonNull(string);
        Objects.requireNonNull(cipher);

        byte[] data = null;

        try {
            data = string.getBytes(StandardCharsets.UTF_8.name());
        } catch (UnsupportedEncodingException e1) {};

        ByteArrayOutputStream bytesOutput = new ByteArrayOutputStream();
        bytesOutput.write(type);
        bytesOutput.write(subType);
        bytesOutput.write(data);

        byte[] plainBytes = bytesOutput.toByteArray();
        byte[] bytes = null;

        try {
            bytes = cipher.doFinal(plainBytes);
        } catch (Exception e) {
            e.printStackTrace();
        }

        byte[] base64Bytes = Base64.getEncoder().encode(bytes);

        return base64Bytes; 
    }

但是当我用下面的代码替换它时，客户端出现了illegalblocksizeexception。

public static byte[] encode(byte type, byte subType, String string, Cipher cipher) 
throws NullPointerException, EncodingException {

        Objects.requireNonNull(string);
        Objects.requireNonNull(cipher);

        byte[] data = null;

        try {
            data = string.getBytes(StandardCharsets.UTF_8.name());
        } catch (UnsupportedEncodingException e1) {};

        CipherOutputStream cipherOutput = null;

        try {
            ByteArrayOutputStream bytesOutput = new ByteArrayOutputStream();
            OutputStream base64Output = Base64.getEncoder().wrap(bytesOutput);
            cipherOutput = new CipherOutputStream(base64Output, cipher);
            cipherOutput.write(type);
            cipherOutput.write(subType);
            cipherOutput.write(data);
            cipherOutput.flush();

            byte[] bytes = bytesOutput.toByteArray();

            return bytes;

        } catch (IllegalStateException | IOException e) {
            throw new EncodingException(e);

        } finally {

            if (cipherOutput != null)
                try {
                    cipherOutput.close();
                } catch (IOException e) {};
            }
        }
}

第二种方法有什么问题？两种方法使用相同的密码。除了encode方法外，服务器上没有任何更改。