Ler certificado digital em Java

LerCertificado.java

publicclass LerCertificado extends HttpServlet {
  protectedvoid doGet(HttpServletRequest request,
  HttpServletResponse response) throws ServletException, IOException {
    PrintWriter out = response.getWriter();
    out.println("");
    out.println("ServletLerCertificado");
    out.println("");
    out.println("Certificado digital:");
    
    String cipherSuite = (String) request.getAttribute("javax.servlet.request.cipher_suite");
    if (cipherSuite != null) {
      java.security.cert.X509Certificate certChain[] = (java.security.cert.X509Certificate[]) 
        request.getAttribute("javax.servlet.request.X509Certificate");
        
      System.out.println("Array size: " + certChain.length);
      if (certChain != null) {
        for (int i = 0; i < certChain.length; i++) {
          String certInfo = "Client Certificate [" + i + "] = " + certChain[i].toString();
          out.println(certInfo);
        }
      }
    } else {
      out.println("Cliente sem Certificado Digital");
    }
    
    out.println("");//new line
    out.close();
  }
}