OAuth 2.0 protocol was made in 2006 and is used for authentication and authorization  in the most of the web services from today ( in special REST service ) in two words you can authenticate users in Web applications via redirects, in Javascript or in desktop and mobile applications. Let’s take a look at the following schema (see more on http://www.ibm.com/developerworks/web/library/wa-oauthsupport/?ca=drs-) this schema may be referenced as tree legged OAuth dance. This protocol ensure a simple way to access some private resource with a access token. So enough with the theory now is time for practice:

/**
* Authenticate on Facebook as user
*
* @param request
*            Servlet request
* @param response
*            Servlet response
* @param scope
*            Comma separated permissions
* @see http://developers.facebook.com/docs/authentication/permissions
* @throws IOException
*/
public void authenticateAsUser(String scope) throws IOException {

log.info(“Executing FB AUTH”);

// ‘extract’ HTTP request and response

HttpServletResponse httpResponse = (HttpServletResponse) response;

// Check if the user is authenticated already
if (getFacebookToken() != null) {
log.info(“User is already autheticated”);
return;
}

// Get the code parameter posted by Facebook
String code = request.getParameter(“code”);

// The callback URL
String nextURL = fbAppCanvasURL;

log.info(nextURL);

// OAuth step 1
if (code == null) {

log.info(“Auth steph 1″);

@SuppressWarnings(“deprecation”)
String requestAdress = String
.format(“https://graph.facebook.com/oauth/authorize?client_id=%s&canvas=true&display=page&redirect_uri=%s&scope=%s”,
fbClientAppId, URLEncoder.encode(nextURL), scope);

log.info(requestAdress);

// Make a call to Facebook to invoke authentication
// httpResponse.sendRedirect(requestAdress);
String out = String
.format(“<script type=\”text/javascript\”>\ntop.location.href = \”%s\”;\n</script>”,
requestAdress);
httpResponse.getWriter().print(out);
httpResponse.flushBuffer();

log.info(“End of steph 1″);

}
// OAuth step 2
// the ‘code’ parameter is sent in the 2′nd authentication phase
// if we have the code param the we are in the 2′nd phase
else {
log.info(“Auth steph 2″);

// request URL to make the 2′nd call to Facebook
@SuppressWarnings(“deprecation”)
String requestAdress = String
.format(“https://graph.facebook.com/oauth/access_token?client_secret=%s&code=%s&client_id=%s&redirect_uri=%s”,
fbClientAppSecret, URLEncoder.encode(code),
fbClientAppId, URLEncoder.encode(nextURL));

log.info(requestAdress);

// The 2′nd phase doesen’t involve the user interaction
// so we can read the result directly on server with a stream reader
URL requestURL = new URL(requestAdress);

// Open a connection to Facebook
BufferedReader in = new BufferedReader(new InputStreamReader(
requestURL.openStream()));

// Read the response and store the result in
// resultString buffer
String inputLine;
StringBuilder resultString = new StringBuilder();

while ((inputLine = in.readLine()) != null)
resultString.append(inputLine);

// Close the connection stream
in.close();

log.info(“Response string:”);
log.info(resultString.toString());

// fetch access token & expiration time from response string
String[] params = resultString.toString().split(“&”);
params[0] = params[0].split(“access_token=”)[1];
// params[1] = params[1].split(“expires=”)[1];

// Store them in cookies
log.info(“Store them in cookies”);
log.info(params[0]);

httpResponse.addCookie(new Cookie(“FB_ACCESS_TOKEN”, params[0]));

// httpResponse.addCookie(new Cookie(“FB_EXPIRE”,
// params[1]));

log.info(“End of steph 2″);
log.info(“Exiting Facebook authentication”);

}

}

Now that we know what is XML good for is time to get in to the business and write out first class that cam be serialized as XML.

C#

using System.Xml.Serialization;
[XmlRoot(ElementName = "PersonalInformations")]

public class PersonalInformations
{
[XmlAttribute(AttributeName="name")]
public string Name { get; set; }

[XmlAttribute(AttributeName="age")]
public uint Age { get; set; }
[XmlAttribute(AttributeName="birth")]
public DateTime DateOfBirth { get; set; }

public string Adress{get;set;}

public static void StoreObject(Stream outStream, PersonalInformations obj)
{
XmlSerializer x = new XmlSerializer(typeof(PersonalInformations));
x.Serialize(outStream, obj);
}
}
public static PersonalInformations LoadObject(Stream inStream)
{
XmlSerializer x = new XmlSerializer(typeof(PersonalInformations));
return  x.Deserialize(inStream) as PersonalInformations;
}
}

Java

@Root(name="PersonalInformations")
class PersonalInformations {

@Attribute(name="name")
private String name;

@Attribute(name="age")
private int age;

@Attribute(name="birth")
private Date dateOfBirth;

@Element(name="birth")
private Date dateOfBirth;

public static void storeObject(Stream outStream, PersonalInformations obj)

{
      Serializer serializer = new Persister();
      serializer.write(obj, outStream);
}

}

public static PersonalInformations loadObject(Stream inStream)

{
      Serializer serializer = new Persister();
      return (PersonalInformations) serializer.read (PersonalInformations.class,inStream);
}

}

In the case of C# we made use of the classes from System.Xml.Serialization namespace, that offers a simple way to serialize classes. In case of Java we use a third part library that can be downloaded from http://simple.sourceforge.net. In both cases we annote the class fields to inform the serialization service about the way we want to create the XML.
As you maybe have already noticed from this sample, XML has become more then a way to store structured information, it is actually a way to express an object state. State that can be stored or sent across applications, applications that can be write in different programming languages.

The goal of this post is not informing about how to serialize classes to XML but to show the simplicity and beauty of XML in communication between applications.

import javax.swing.event.HyperlinkEvent;
import javax.swing.*;
import java.io.*;
import javax.swing.event.HyperlinkListener;

public class SimpleWebBrowser {
static JEditorPane jep = new JEditorPane();
public static void main(String[] args) {

String initialPage = “http://www.google.ro/”;
if (args.length > 0) initialPage = args[0];

jep.setEditable(false);

jep.addHyperlinkListener(new HyperlinkListener() {

public void hyperlinkUpdate(HyperlinkEvent e) {
try {
jep.setPage(e.getURL());
} catch (IOException ex) {
Logger.getLogger(SimpleWebBrowser.class.getName()).log(Level.SEVERE, null, ex);
}
}
});

try {
jep.setPage(initialPage);
}
catch (IOException e) {
System.err.println(“Usage: java SimpleWebBrowser url”);
System.err.println(e);
System.exit(-1);
}

JScrollPane scrollPane = new JScrollPane(jep);
JFrame f = new JFrame(“Simple Web Browser”);
f.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
f.getContentPane().add(scrollPane);
f.setSize(512, 342);
f.show();

}

}

Si iata cum ar arata “miniborwser-ul”