I have seen that most the cases, You may need to retrieve the X509 Certificate as <ds:X509Certificate> Data. <ds:X509Certificate> data can be seen in SOAP messages (SAML, WS-Security) that are passed the security information. You can easily retrieve X509Certificate data using java keytool command.
If you want to retrieve X509Certificate data from key store file (JKS)
keytool -export -keystore pathToKeystore -rfc -alias aliasNameForCertificate
If you want to retrieve X509Certificate data from certificate file ( .cert, .pem and etc)
keytool -printcert -rfc -file pathToCertificate
Following is the output that I retrieve from wso2carbon certificate that contains in the WSO2 Carbon product
>keytool -printcert -rfc -file wso2.cert -----BEGIN CERTIFICATE----- MIICNTCCAZ6gAwIBAgIES343gjANBgkqhkiG9w0BAQUFADBVMQswCQYDVQQGEwJVUzELMAkGA1UE CAwCQ0ExFjAUBgNVBAcMDU1vdW50YWluIFZpZXcxDTALBgNVBAoMBFdTTzIxEjAQBgNVBAMMCWxv Y2FsaG9zdDAeFw0xMDAyMTkwNzAyMjZaFw0zNTAyMTMwNzAyMjZaMFUxCzAJBgNVBAYTAlVTMQsw CQYDVQQIDAJDQTEWMBQGA1UEBwwNTW91bnRhaW4gVmlldzENMAsGA1UECgwEV1NPMjESMBAGA1UE AwwJbG9jYWxob3N0MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCUp/oV1vWc8/TkQSiAvTou sMzOM4asB2iltr2QKozni5aVFu818MpOLZIr8LMnTzWllJvvaA5RAAdpbECb+48FjbBe0hseUdN5 HpwvnH/DW8ZccGvk53I6Orq7hLCv1ZHtuOCokghz/ATrhyPq+QktMfXnRS4HrKGJTzxaCcU7OQID AQABoxIwEDAOBgNVHQ8BAf8EBAMCBPAwDQYJKoZIhvcNAQEFBQADgYEAW5wPR7cr1LAdq+IrR44i QlRG5ITCZXY9hI0PygLP2rHANh+PYfTmxbuOnykNGyhM6FjFLbW2uZHQTY1jMrPprjOrmyK5sjJR O4d1DeGHT/YnIjs9JogRKv4XHECwLtIVdAbIdWHEtVZJyMSktcyysFcvuhPQK8Qc/E/Wq8uHSCo= -----END CERTIFICATE-----
Also, following is the simple java code that you can retrieve the certificate data as String from a give certificate file
// build input stream using certificate file InputStream inputStream = new FileInputStream(filePath); // build X509Certificate object X509Certificate certificate = new X509CertImpl(inputStream); // get byte value of certificate byte[] value = certificate.getEncoded(); // encode the value BASE64Encoder encoder=new BASE64Encoder(); String encodedValue = encoder.encode(value);