How to check if web service is available, and then connect to it in one go?

Question

I want to check if a web service is available before connecting to it, so that if it is not available, I can display a dialog that says so. My first attempt is this:

public void isAvailable(){

    // first check if there is a WiFi/data connection available... then:

    URL url = new URL("URL HERE");
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestProperty("Connection", "close");
    connection.setConnectTimeout(10000); // Timeout 10 seconds
    connection.connect();

    // If the web service is available
    if (connection.getResponseCode() == 200) {
        return true;
    }
    else return false;
}

And then in a separate class I do

if(...isAvailable()){
    HttpPost httpPost = new HttpPost("SAME URL HERE");
    StringEntity postEntity = new StringEntity(SOAPRequest, HTTP.UTF_8);
    postEntity.setContentType("text/xml");
    httpPost.setHeader("Content-Type", "application/soap+xml;charset=UTF-8");
    httpPost.setEntity(postEntity);

    // Get the response
    HttpClient httpclient = new DefaultHttpClient();
    BasicHttpResponse httpResponse = (BasicHttpResponse) httpclient.execute(httpPost);

    // Convert HttpResponse to InputStream for parsing
    HttpEntity responseEntity = httpResponse.getEntity();
    InputStream soapResponse = responseEntity.getContent();

    // Parse the result and do stuff with the data...
}

However I'm connecting to the same URL twice, and this is inefficient and probably slowing down my code.

First of all, is it?

Secondly, what's a better way to do this?

score 3 · Accepted Answer · answered Oct 16 '12 at 17:15

3

I would just try connecting, if it times out, handle the exception, and display an error.

answered Oct 16 '12 at 17:15

dardo

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What do I check for to see if it times out? The exceptions I'm catching are `UnsupportedEncodingException`, `ClientProtocolException`, `IOException` `ParserConfigurationException`, and `SAXException`... – Kalina Oct 16 '12 at 17:17
1

Believe the timeout exception derives from IOException, I'd look at this wiki post: http://stackoverflow.com/questions/2793150/how-to-use-java-net-urlconnection-to-fire-and-handle-http-requests, if all else fails, try entering a bogus URL and see what exception is thrown. – dardo Oct 16 '12 at 17:21
You're right, it's IOException. However, now that I tried this, I remember why I didn't do it this way in the first place... Because I can't show a dialog from a non-UI thread... That's a different issue though, so thanks! – Kalina Oct 16 '12 at 17:27
Android should have a managed "session" like context that you could probably populate on an error. Also, accept the answer if it solved the problem. – dardo Oct 16 '12 at 17:29

score 0 · Answer 2 · answered Oct 16 '12 at 17:31

May be you should consider looking at HttpConnectionParams class methods.

public static void setConnectionTimeout (HttpParams params, int timeout)

Sets the timeout until a connection is etablished. A value of zero means the timeout is not used. The default value is zero.

public static void setSoTimeout (HttpParams params, int timeout)

Sets the default socket timeout (SO_TIMEOUT) in milliseconds which is the timeout for waiting for data. A timeout value of zero is interpreted as an infinite timeout. This value is used when no socket timeout is set in the method parameters.

Hope this helps.

How to check if web service is available, and then connect to it in one go?

2 Answers2