Question

I am trying to refactor (to take advantage of Guava) some code that sends a POST request to a web service and reads the reply to a string.

Currently my code looks like that:

    HttpURLConnection conn = null;
    OutputStream out = null;

    try {
        // Build the POST data (a JSON object with the WS params)
        JSONObject wsArgs = new JSONObject();
        wsArgs.put("param1", "value1");
        wsArgs.put("param2", "value2");
        String postData = wsArgs.toString();

        // Setup a URL connection
        URL address = new URL(Constants.WS_URL);
        conn = (HttpURLConnection) address.openConnection();
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/json");
        conn.setUseCaches(false);
        conn.setDoOutput(true);
        conn.setConnectTimeout(Constants.DEFAULT_HTTP_TIMEOUT);

        // Send the request
        out = conn.getOutputStream();
        out.write(postData.getBytes());
        out.close();

        // Get the response
        int responseCode = conn.getResponseCode();
        if (responseCode != 200) {
            Log.e("", "Error - HTTP response code: " + responseCode);
            return Boolean.FALSE;
        } else {
            // Read conn.getInputStream() here
        }
    } catch (JSONException e) {
        Log.e("", "SendGcmId - Failed to build the WebService arguments", e);
        return Boolean.FALSE;
    } catch (IOException e) {
        Log.e("", "SendGcmId - Failed to call the WebService", e);
        return Boolean.FALSE;
    } finally {
        if (conn != null) conn.disconnect();

                    // Any guava equivalent here too?
        IOUtils.closeQuietly(out);
    }

I would like to understand how to use properly Guava’s InputSupplier and OutputSupplier here to get rid of quite a bunch of code. There are quite a few examples out here with files but I can’t get a nice concise version of the above code (would like to see what a Guava experienced user would do with that).

Answer 1

The majority of the simplification you’ll be able to get — such as it is — would be to replace the lines out = conn.getOutputStream(); out.write(postData.getBytes()); out.close(), and the need to close out yourself, with

new ByteSink() {
  public OutputStream openStream() throws IOException {
    return conn.getOutputStream();
  }
}.write(postData.getBytes());

That opens the output stream, writes the bytes, and closes the output stream properly (as opposed to closeQuietly).