Read input-stream without 3rd library anyway

readFromInputStream.java

  public static String readFromInputStream(InputStream is) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder builder = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            builder.append(line);
        }
        return builder.toString();
    }

This drops line endings, so it does not convert the input data without loss.