Generate X509Certificate from byte[]?
Sure.
The certificate objects can be created by an instance of CertificateFactory - in particular, one configured to create X509 certificates. This can be created like so:
CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
Then you need to pass it an InputStream containing the bytes of the certificate. This can be achieved by wrapping your byte array in a ByteArrayInputStream:
InputStream in = new ByteArrayInputStream(bytes);
X509Certificate cert = (X509Certificate)certFactory.generateCertificate(in);