http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.cert.jcajce;

import java.security.cert.X509Certificate;

import org.bouncycastle.asn1.x500.X500Name;
import org.bouncycastle.asn1.x500.X500NameStyle;

public class JcaX500NameUtil
{
    public static X500Name getIssuer(X509Certificate certificate)
    {
        return X500Name.getInstance(certificate.getIssuerX500Principal().getEncoded());
    }

    public static X500Name getSubject(X509Certificate certificate)
    {
        return X500Name.getInstance(certificate.getSubjectX500Principal().getEncoded());
    }

    public static X500Name getIssuer(X500NameStyle style, X509Certificate certificate)
    {
        return X500Name.getInstance(style, certificate.getIssuerX500Principal().getEncoded());
    }

    public static X500Name getSubject(X500NameStyle style, X509Certificate certificate)
    {
        return X500Name.getInstance(style, certificate.getSubjectX500Principal().getEncoded());
    }
}