试图阅读cloudstorage.properties。获取NullPointerException

Question

我在我的应用中使用Google云端存储时出现问题，基本上我失败的地方是从此行检索GoogleCredential，这给了我一个NullPointerException =

GoogleCredential credential = new GoogleCredential.Builder()

我正在尝试获取Google应用程序默认凭据，但我没有使用Google Compute Engine，我更喜欢使用Google App Engine。

我正在使用这行代码来制作这个负责上传和下载文件的方法=

private static Storage getStorage() {
        if (storage == null) {
            HttpTransport httpTransport = new NetHttpTransport();
            JsonFactory jsonFactory = new JacksonFactory();

            List<String> scopes = new ArrayList<>();
            scopes.add(StorageScopes.DEVSTORAGE_FULL_CONTROL);

            try {
                GoogleCredential credential = new GoogleCredential.Builder()
                        .setTransport(httpTransport)
                        .setJsonFactory(jsonFactory)
                        .setServiceAccountId(
                                getProperties().getProperty(ACCOUNT_ID_PROPERTY))
                        .setServiceAccountPrivateKeyFromP12File(
                                new File(getProperties().getProperty(
                                        PRIVATE_KEY_PATH_PROPERTY)))
                        .setServiceAccountScopes(scopes).build();

                storage = new Storage.Builder(httpTransport, jsonFactory,
                        credential).setApplicationName(
                        getProperties().getProperty(APPLICATION_NAME_PROPERTY))
                        .build();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return storage;
    }

在问题中添加更多内容，调试后我注意到给出我nullPointerException的行在这个方法中=

private static Properties getProperties() throws Exception {

        if (properties == null) {
            properties = new Properties();
            InputStream stream = CloudStorage.class
                    .getResourceAsStream("/cloudstorage.properties");
            try {
                properties.load(stream);
            } catch (IOException e) {
                throw new RuntimeException(
                        "cloudstorage.properties must be present in classpath",
                        e);
            } finally {
                stream.close();
            }
        }
        return properties;
    }

特别是这行代码=

InputStream stream = CloudStorage.class
                        .getResourceAsStream("/cloudstorage.properties");