How to extract X509 Certificate fields in Java

Question

I am currently working on an application that will process certain fields of a X509 Certificate, and I cannot seem to figure out how to extract certain parts of the certificate for debugging purposes. So far I have only been able to figure out how to read a certificate from a file based on the Javadoc for java.security.cert.Certificate, using this code:

FileInputStream fis = new FileInputStream(filename);
BufferedInputStream bis = new BufferedInputStream(fis);

CertificateFactory cf = CertificateFactory.getInstance("X.509");
while (bis.available() > 0) {
    Certificate cert = cf.generateCertificate(bis);
System.out.println(cert.toString());
}

Assuming that no exceptions are thrown, and that cert is a valid certificate, how would I do this?

Sidenote I am using Bouncy Castle in this project

Answer 1

Cast it to an X509Certificate:

X509Certificate cert = (X509Certificate) cf.generateCertificate(bis);
System.out.println(cert.getSubjectDN());