Using CertificateFactory Class to Read in Certificates

JDK Tutorials - Herong's Tutorial Examples

∟Using CertificateFactory Class to Read in Certificates

This section provides a tutorial example on how to write a sample program to read in certificate files with the java.security.cert.CertificateFactory class.

java.security.cert.CertificateFactory is a class to read in different types of certificates from certificate files.

getIntance() - Returns a CertificateFactory object of the specified certificate type using the implementation of the specified security package provider. If not specified, the default provider will used.
generateCertificate() - Read in a certificate from the specified input stream, and returns it as a Certificate object. It can read certificate in both binary (DER encoded) and printable (RFC standard) formats. Note that only the first certificate in the input stream will be processed.
generateCertificates() - Read in multiple certificates from the specified input stream, and returns them as a Certificate array. It can read certificate in both binary (DER encoded) and printable (RFC standard) formats.
getType() - Returns the type of this certificate factory.
getProvider() - Returns the security package provider.

In the following sample program, I want to show you how to read in a certificate from a certificate file, and write it out to a certificate file in the default encoding format.

/* JcaCertificateTest.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.io.*;
import java.security.*;
import java.security.cert.*;
class JcaCertificateTest {
   public static void main(String[] a) {
      if (a.length<2) {
         System.out.println("Usage:");
         System.out.println("java JcaCertificateFactoryTest input"
            +" output");
         return;
      }
      String input = a[0];
      String output = a[1];
      try {
         test(input,output);
      } catch (Exception e) {
         System.out.println("Exception: "+e);
         return;
      }
   }
   private static void test(String input, String output)
      throws Exception {
      CertificateFactory cf = CertificateFactory.getInstance("X.509");
      System.out.println();
      System.out.println("CertificateFactory Object Info: ");
      System.out.println("Type = "+cf.getType());
      System.out.println("Provider = "+cf.getProvider());
      System.out.println("toString = "+cf.toString());

      FileInputStream fis = new FileInputStream(input);
      java.security.cert.Certificate cert = cf.generateCertificate(fis);
      fis.close();
      System.out.println();
      System.out.println("Certificate Object Info: ");
      System.out.println("Type = "+cert.getType());
      System.out.println("toString = "+cert.toString());

      PublicKey pubKey = cert.getPublicKey();
      System.out.println();
      System.out.println("PublicKey Object Info: ");
      System.out.println("Algorithm = "+pubKey.getAlgorithm());
      System.out.println("Format = "+pubKey.getFormat());
      System.out.println("toString = "+pubKey.toString());

      FileOutputStream fos = new FileOutputStream(output);
      byte[] certBytes = cert.getEncoded();
      fos.write(certBytes);
      fos.close();
   }
}