How to create a X509 certificate using Java?

For JDK versions <17, you can also generate a certificate using only JDK classes. The disadvantage is that you have to use two classes from the package.
The code would be:

KeyStore keyStore = ... // your keystore

// generate the certificate
// first parameter  = Algorithm
// second parameter = signrature algorithm
// third parameter  = the provider to use to generate the keys (may be null or
//                    use the constructor without provider)
CertAndKeyGen certGen = new CertAndKeyGen("RSA", "SHA256WithRSA", null);
// generate it with 2048 bits

// prepare the validity of the certificate
long validSecs = (long) 365 * 24 * 60 * 60; // valid for one year
// add the certificate information, currently only valid for one year.
X509Certificate cert = certGen.getSelfCertificate(
   // enter your details according to your application
   new X500Name("CN=My Application,O=My Organisation,L=My City,C=DE"), validSecs);

// set the certificate and the key in the keystore
keyStore.setKeyEntry(certAlias, certGen.getPrivateKey(), null, 
                        new X509Certificate[] { cert });

Retrieve the private key from the key store to encrypt or decrypt data.
Based on the code is from—-3

Leave a Comment