Exchange Cookie

One interesting aspect in HTTP protocol is the cookie management. As we know HTTP is a stateless protocol so using cookies we can persist some information across HTTP requests. As example we can suppose to make two HTTP request: one where we invoke a URL and the server returns a cookie containing some information and another one where we send back to the server the cookie.

The first request is very simple:

1	HttpPost post = new HttpPost(url);

2	HttpResponse resp = client.execute(post);

Then we read the cookie (line 1,3):

01	CookieStore store = ((DefaultHttpClient) client).getCookieStore();

02

03	List<Cookie> cookies = store.getCookies();

04	if (cookies != null) {

05	for (Cookie c : cookies) {

06	System.out.println("Name ["+c.getName()+"] - Val ["+c.getValue()+"]

07	- Domain ["+c.getDomain()+"] - Path ["+c.getPath()+"]");

08	store.addCookie(c);

09

}

10

}

At line 1 we simply get the cookie store where the cookies are stored. At line 3 we retrieves the cookies list. In the second post request we have to maintain the cookie we retrieved in the first request so we have:

1	HttpContext ctx = new BasicHttpContext();

2	ctx.setAttribute(ClientContext.COOKIE_STORE, store);

3

4	// Post again with cookie

5	HttpPost post1 = new HttpPost(url);

6	client.execute(post1);

7	HttpResponse resp1 = client.execute(post, ctx);

At line 1 we create BasicHttpContext to handle cookies and at line 2 we set the store inside our context and finally at line 7 we execute the request passing the context too.

One thing we have to notice is that the DefaultHttpClient is always the same so that we can re-use the cookies.

Running the example we have:

Client side cookie output	Server side cookie output