etag comparision code example

Question

I'm trying to simulate a process like "cache validation" in my application. I will download a new version of my webapplication on the device (android-based), but I only want to download a new version of the files, based in a etag comparision. Does anyone a example of how use the Etag mechanism in Android?

score 1 · Answer 1 · answered Jan 09 '13 at 21:10

You can access the ETag field from a HttpURLConnection object such as like this:

HttpURLConnection conn = (HttpURLConnection)new URL(url).openConnection();
String etag = conn.getHeaderField("ETag");

Of course, you will need to make sure that the server you are testing this against supports ETags.

score 0 · Answer 2 · answered Dec 14 '12 at 14:39

Maybe class "HttpRequest" from this library (kevinsawicki) will help you.

For example:

File latest = new File("/data/cache.json");
HttpRequest request = HttpRequest.get("http://google.com");
//Copy response to file
request.body(latest);
//Store eTag of response
String eTag = request.eTag();

//Later you can check if changes exist
boolean unchanged = HttpRequest.get("http://google.com")
                           .ifNoneMatch(eTag)
                           .notModified();

score 0 · Answer 3 · answered Oct 23 '13 at 17:27

HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
try {
            HttpResponse response = httpClient.execute(httpPost);
            Log.d("Http Response:", response.getFirstHeader("etag").toString());

        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

score 0 · Answer 4 · answered Dec 22 '16 at 08:42

0

You can refer to the specific implement of ShallowEtagHeaderFilter performing etag generation and validation in Spring.

answered Dec 22 '16 at 08:42

Sunny

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etag comparision code example

4 Answers4