Different ways to access HTTP resources from Android（cf）

from:  http://blog.dahanne.net/2009/08/16/how-to-access-http-resources-from-android/

First Method : getting an input stream given a simple url from Android using HttpURLConnection

This method is the most basic one : it allows you, using the basic HttpUrlConnection, ( contained in java.net) to get an InputStream from an Url :

 

private InputStream downloadUrl(String url) {
		HttpURLConnection con = null;
		URL url;
		InputStream is=null;
		try {
			url = new URL(url);
			con = (HttpURLConnection) url.openConnection();
			con.setReadTimeout(10000 /* milliseconds */);
			con.setConnectTimeout(15000 /* milliseconds */);
			con.setRequestMethod("GET");
			con.setDoInput(true);
			con.addRequestProperty("Referer", "http://blog.dahanne.net");
			// Start the query
			con.connect();
			is = con.getInputStream();
		}catch (IOException e) {
                        //handle the exception !
			e.printStackTrace();
		}
		return is;
 
	}

 

You can also use the Post method, sending data in the HTTP POST payload :

 

private InputStream downloadUrl(String url) {
                InputStream myInputStream =null;
		StringBuilder sb = new StringBuilder();
                //adding some data to send along with the request to the server
		sb.append("name=Anthony");
		URL url;
		try {
			url = new URL(url);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setDoOutput(true);
			conn.setRequestMethod("POST");
			OutputStreamWriter wr = new OutputStreamWriter(conn
					.getOutputStream());
                        // this is were we're adding post data to the request
                        wr.write(sb.toString());
			wr.flush();
			myInputStream = conn.getInputStream();
			wr.close();
		} catch (Exception e) {
                        //handle the exception !
			Log.d(TAG,e.getMessage());
		}
                return myInputStream;
}

 

But there are better ways to achieve that, using Apache HttpClient, included in android.jar (no need to add another jar, it’s included in android core)

Second Method : getting an input stream given a simple url from Android using HttpClient

Why is it a better to do it ? because the simpler, the better ! See by yourself :

 

public static InputStream getInputStreamFromUrl(String url) {
		InputStream content = null;
		try {
			HttpGet httpGet = new HttpGet(url);
			HttpClient httpclient = new DefaultHttpClient();
			// Execute HTTP Get Request
			HttpResponse response = httpclient.execute(httpGet);
			content = response.getEntity().getContent();
                } catch (Exception e) {
			//handle the exception !
		}
		return content;
}

 

But you maybe wondering if it’s still easy with HTTP Post method ? You won’t be deceived !

 

 

public static InputStream getInputStreamFromUrl(String url) {
		InputStream content = null;
		try {
          		HttpClient httpclient = new DefaultHttpClient();
			HttpPost httpPost = new HttpPost(url);
			List nameValuePairs = new ArrayList(1);
                        //this is where you add your data to the post method
                        nameValuePairs.add(new BasicNameValuePair(
			"name", "anthony"));
			httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
			// Execute HTTP Post Request
			HttpResponse response = httpclient.execute(httpPost);
			content = response.getEntity().getContent();
		        return content;
	        }
}

 But what if you want to read a cookie from the response ? And how can you send a cookie back to the server for the next request ?

 

Reading / Sending a cookie along with the requests

 

Using Apache HttpClient, it’s easy to retrieve cookies ! Everything is in the headers after all !

 

[...]
Cookie sessionCookie =null;
HttpResponse response = httpclient.execute(httpPost);
Header[] allHeaders = response.getAllHeaders();
CookieOrigin origin = new CookieOrigin(host, port,path, false);
for (Header header : allHeaders) {
			List parse = cookieSpecBase.parse(header, origin);
			for (Cookie cookie : parse) {
				// THE cookie
				if (cookie.getName().equals(COOKIE_I_WAS_LOOKING_FOR)
						&& cookie.getValue() != null && cookie.getValue() != "") {
					sessionCookie = cookie;
				}
			}
}

 

 To send a cookie along with your request, keep it simple :

 

HttpPost httpPost = new HttpPost(url);
CookieSpecBase cookieSpecBase = new BrowserCompatSpec();
List cookies = new ArrayList();
cookies.add(sessionCookie);
List cookieHeader = cookieSpecBase.formatCookies(cookies);
// Setting the cookie
httpPost.setHeader(cookieHeader.get(0));

 What about the resulting InputStream ? You definitely want to transform it into a String or an Drawable (to set it to an ImageView for example !) don’t you ?

Converting the InputStream into a Drawable in Android

The Drawable class already handles that for you :

 

Drawable d = Drawable.createFromStream(myInputStream, "nameOfMyResource");

 

Converting the InputStream into a String in Android

This is some classic java stuff (don’t tell about how easier it is in Ruby.. I know  … but hey ! Java SE7 at the rescue with NIO !!! maybe one day in 2010 ! )

 

BufferedReader rd = new BufferedReader(new InputStreamReader(myInputStreamToReadIntoAString), 4096);
String line;
StringBuilder sb =  new StringBuilder();
while ((line = rd.readLine()) != null) {
		sb.append(line);
}
rd.close();
String contentOfMyInputStream = sb.toString()
 
That's it folks ! If you have any other methods to achieve these goals, feel free to share them sending a comment !