I am trying to follow https://developers.google.com/identity/protocols/oauth2/web-server#exchange-authorization-code to exchange a code for an access token. I am able to get my local endpoint to trigger and in the controller I run the following. The issue is that I am getting a 400 from ‘https://oauth2.googleapis.com/token’ endpoint. I do not see a response body, which is where would usually look for the error message. Does anyone know how I can debug or what the issue might be? Note that I have ‘http://localhost:8080/oauthtokengmail’ as one of my ‘Authorized redirect URIs’, and that the redirect is working, so I do not think the issue is there.

I was successfully able to use curl to get the values … so I know it must be something in the java code.

I am executing the following code:

private String getTokenJson(String code, boolean isProduction) {

        RequestConfig requestConfig = getRequestConfig();
        BasicHttpClientConnectionManager cm = getConnectionManager();

        HttpPost post = new HttpPost("https://oauth2.googleapis.com/token");

        List<NameValuePair> pairs = new ArrayList<>();
        pairs.add(new BasicNameValuePair("code", code));
        pairs.add(new BasicNameValuePair("client_id", gmailSecretsService.getClientId()));
        pairs.add(new BasicNameValuePair("client_secret", gmailSecretsService.getClientSecret()));
        pairs.add(new BasicNameValuePair("grant_type", "authorization_code"));
        pairs.add(new BasicNameValuePair("redirect_uri", getRedirectUri(isProduction)));

        post.setEntity(new UrlEncodedFormEntity(pairs));

        //////////////////////
        try (CloseableHttpClient httpclient = HttpClientBuilder.create()
                .setDefaultRequestConfig(requestConfig)
                .setConnectionManager(cm)
                .build()) {
            try (CloseableHttpResponse response = httpclient.execute(post)) {
                // Get status code
                if (response.getCode() != 200) {
                    LOGGER.info("Seeing response.code()={}", response.getCode());
                    return null;
                }
                HttpEntity entity = response.getEntity();
                // Get response information
                String resultContent = EntityUtils.toString(entity);
                LOGGER.info("Seeing result={}", resultContent);
                return resultContent;
            }

        } catch (IOException | ParseException e) {
            LOGGER.info("Seeing exception", e);
            return null;
        }
    }

private static BasicHttpClientConnectionManager getConnectionManager() {
        ConnectionConfig connConfig = ConnectionConfig.custom()
                .setConnectTimeout(15000, TimeUnit.MILLISECONDS)
                .setSocketTimeout(15000, TimeUnit.MILLISECONDS)
                .build();
        BasicHttpClientConnectionManager cm = new BasicHttpClientConnectionManager();
        cm.setConnectionConfig(connConfig);
        return cm;
    }

    private static RequestConfig getRequestConfig() {
        return RequestConfig.custom()
                .setConnectionRequestTimeout(Timeout.ofMilliseconds(15000))
                .build();
    }


private static String getRedirectUri(boolean isProduction) {
        if (isProduction) {
            return "https://example.com/oauthtokengmail";
        } else {
            return "http://localhost:8080/oauthtokengmail";
        }
    }