protected String readJsonStringFromUri(@NonNull final ContentResolver contentResolver, @NonNull final Uri uri) throws IOException {
        final StringBuilder stringBuilder = new StringBuilder();
        final InputStream inputStream = contentResolver.openInputStream(uri);
        if (inputStream != null) {
            final BufferedReader reader = new BufferedReader(new InputStreamReader(
                    inputStream));
            String line;
            while ((line = reader.readLine()) != null) {
                stringBuilder.append(line);
            }
            reader.close();
            inputStream.close();
        }
        return stringBuilder.toString();
    }
Reads and returns the json string from URI.

@param contentResolver ContentResolver
@param uri             URI
@throws IOException in case of failure
mesh/src/main/java/no/nordicsemi/android/mesh/ImportExportUtils.java