JWT Reading private key in Spring - spring

Question

I have this service class that reads a private key from the classpath. The class is as follows:
#Component
#RequiredArgsConstructor
public class JwtKeyProvider {
private final ResourceUtil resourceUtil;
private final Base64Util base64Util;
#Getter
private PrivateKey privateKey;
#PostConstruct
public void init() {
privateKey = readKey(
"classpath:keys/scbpeopleintranetdev_sha1withrsa.pkcs8.private",
"PRIVATE",
this::privateKeySpec,
this::privateKeyGenerator
);
}
private <T extends Key> T readKey(String resourcePath, String headerSpec, Function<String, EncodedKeySpec> keySpec, BiFunction<KeyFactory, EncodedKeySpec, T> keyGenerator) {
try {
String keyString = resourceUtil.asString(resourcePath);
//TODO you can check the headers and throw an exception here if you want
keyString = keyString
.replace("-----BEGIN " + headerSpec + " KEY-----", "")
.replace("-----END " + headerSpec + " KEY-----", "")
.replaceAll("\\s+", "");
return keyGenerator.apply(KeyFactory.getInstance("RSA"), keySpec.apply(keyString));
} catch(NoSuchAlgorithmException | IOException e) {
throw new JwtInitializationException(e);
}
}
private EncodedKeySpec privateKeySpec(String data) {
return new PKCS8EncodedKeySpec(base64Util.decode(data));
}
private PrivateKey privateKeyGenerator(KeyFactory kf, EncodedKeySpec spec) {
try {
return kf.generatePrivate(spec);
} catch(InvalidKeySpecException e) {
throw new JwtInitializationException(e);
}
}
}
The thing is that my key is in the .key format, not in the .pkcs8 so I'm dealing with this console error:
java.security.InvalidKeyException: IOException : algid parse error, not a sequence
I've tried out converting it to pkcs8 and it works but any one knows how to solve this code avoiding converting it to pkcs8?
Thanks in advance!