How to use

getPrivateKey

method

in

com.google.auth.oauth2.ServiceAccountJwtAccessCredentials

@Override
public byte[] sign(byte[] toSign) {
 try {
  Signature signer = Signature.getInstance(OAuth2Utils.SIGNATURE_ALGORITHM);
  signer.initSign(getPrivateKey());
  signer.update(toSign);
  return signer.sign();
 } catch (NoSuchAlgorithmException | InvalidKeyException | SignatureException ex) {
  throw new ServiceAccountSigner.SigningException("Failed to sign the provided bytes", ex);
 }
}

@Test
public void serviceAccountReplacedWithJwtTokens() throws Exception {
 ServiceAccountCredentials serviceAccountCredentials =
   ServiceAccountCredentials.newBuilder()
     .setClientId("fake-client-id")
     .setClientEmail("fake@example.com")
     .setPrivateKeyId("fake-private-key")
     .setPrivateKey(Mockito.mock(PrivateKey.class))
     .build();
 PowerMockito.mockStatic(GoogleCredentials.class);
 Mockito.when(GoogleCredentials.getApplicationDefault()).thenReturn(serviceAccountCredentials);
 GoogleCredentialsProvider provider =
   GoogleCredentialsProvider.newBuilder()
     .setScopesToApply(ImmutableList.of("scope1", "scope2"))
     .setJwtEnabledScopes(ImmutableList.of("scope1"))
     .build();
 Credentials credentials = provider.getCredentials();
 assertThat(credentials).isInstanceOf(ServiceAccountJwtAccessCredentials.class);
 ServiceAccountJwtAccessCredentials jwtCreds = (ServiceAccountJwtAccessCredentials) credentials;
 assertThat(jwtCreds.getClientId()).isEqualTo(serviceAccountCredentials.getClientId());
 assertThat(jwtCreds.getClientEmail()).isEqualTo(serviceAccountCredentials.getClientEmail());
 assertThat(jwtCreds.getPrivateKeyId()).isEqualTo(serviceAccountCredentials.getPrivateKeyId());
 assertThat(jwtCreds.getPrivateKey()).isEqualTo(serviceAccountCredentials.getPrivateKey());
}

@Test 
public void constructor_allParameters_constructs() throws IOException {
 PrivateKey privateKey = ServiceAccountCredentials.privateKeyFromPkcs8(SA_PRIVATE_KEY_PKCS8);
 ServiceAccountJwtAccessCredentials credentials = ServiceAccountJwtAccessCredentials.newBuilder()
   .setClientId(SA_CLIENT_ID)
   .setClientEmail(SA_CLIENT_EMAIL)
   .setPrivateKey(privateKey)
   .setPrivateKeyId(SA_PRIVATE_KEY_ID)
   .build();
 
 assertEquals(SA_CLIENT_ID, credentials.getClientId());
 assertEquals(SA_CLIENT_EMAIL, credentials.getClientEmail());
 assertEquals(privateKey, credentials.getPrivateKey());
 assertEquals(SA_PRIVATE_KEY_ID, credentials.getPrivateKeyId());
}

@Override
public byte[] sign(byte[] toSign) {
 try {
  Signature signer = Signature.getInstance(OAuth2Utils.SIGNATURE_ALGORITHM);
  signer.initSign(getPrivateKey());
  signer.update(toSign);
  return signer.sign();
 } catch (NoSuchAlgorithmException | InvalidKeyException | SignatureException ex) {
  throw new ServiceAccountSigner.SigningException("Failed to sign the provided bytes", ex);
 }
}

@Test
public void sign_sameAs()
  throws IOException, NoSuchAlgorithmException, InvalidKeyException, SignatureException {
 PrivateKey privateKey = ServiceAccountCredentials.privateKeyFromPkcs8(SA_PRIVATE_KEY_PKCS8);
 byte[] toSign = {0xD, 0xE, 0xA, 0xD};
 ServiceAccountJwtAccessCredentials credentials = ServiceAccountJwtAccessCredentials.newBuilder()
   .setClientId(SA_CLIENT_ID)
   .setClientEmail(SA_CLIENT_EMAIL)
   .setPrivateKey(privateKey)
   .setPrivateKeyId(SA_PRIVATE_KEY_ID)
   .build();
 byte[] signedBytes = credentials.sign(toSign);
 Signature signature = Signature.getInstance(OAuth2Utils.SIGNATURE_ALGORITHM);
 signature.initSign(credentials.getPrivateKey());
 signature.update(toSign);
 assertArrayEquals(signature.sign(), signedBytes);
}