(Java) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkPublicKey pubKey = new CkPublicKey();

    // Load the public key from an PEM file:
    boolean success = pubKey.LoadFromFile("pubKey.pem");
    if (success != true) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    // Load the data of the original file that was signed.
    CkBinData bdFileData = new CkBinData();
    success = bdFileData.LoadFile("in.dat");

    // Load the signature.
    CkBinData bdSig = new CkBinData();
    success = bdSig.LoadFile("signature.sig");

    CkRsa rsa = new CkRsa();

    // Import the public key into the RSA component:
    success = rsa.ImportPublicKeyObj(pubKey);
    if (success != true) {
        System.out.println(rsa.lastErrorText());
        return;
        }

    // OpenSSL uses big-endian.
    rsa.put_LittleEndian(false);

    success = rsa.VerifyBd(bdFileData,"sha256",bdSig);
    if (success != true) {
        System.out.println(rsa.lastErrorText());
        System.out.println("The signature was invalid.");
        return;
        }

    System.out.println("The signature was verified.");
  }
}