6.x Java Extensions CookBook

This document provides quick snippets of code organized by theme that will get you started with most of the server side coding tasks. Feel free to suggest more "recipes" by sending us an email or posting in our support forums

» Login Recipes

By setting the customLogin attribute of a Zone to true you can handle the login event in your server side code. Upon login the server will first perform a series of checkes, like validating the user name and verifying that the user is not in the ban-list. Once the checks are passed it will pass the user details to your server-side extension to handle the rest of the login process. Here you will be able to connect to your database or any other data source and perform your custom logic.

Recipe #1:

We perform a simple validation of the user name against a list of valid user names.

List<String> validNames;	
ExtensionHelper helper;
Zone currentZone;

public void init()
{
	helper = ExtensionHelper.instance();
	currentZone = helper.getZone(this.getOwnerZone);
	
	validNames = new ArrayList<String>();
	validNames.add("Pierre");
	validNames.add("Michelle");
	validNames.add("Gunther");
	validNames.add("Christine");
	validNames.add("Nicole");
}
	
public void handleInternalEvent(InternalEventObject evt)
{
	if (evt.getEventName().equals(InternalEventObject.EVENT_LOGIN))
	{
		boolean ok = false;
		User newUser = null;
		
		// Prepare a response object for the client
		ActionscriptObject response = new ActionscriptObject();
		
		// get the user nickname and password (not used in this example)
		String nick = ieo.getParam("nick");
		String pass = ieo.getParam("pass");
		
		// get the user socket channel
		SocketChannel chan = (SocketChannel) ieo.getObject("chan");
		
		// validate user name
		if (validNames.contains(nick))
			ok = true;
		
		if (ok)
		{
			try
			{
				// Attempt to login the user in the system
				newUser = helper.canLogin(nick, pass, chan, currentZone);

				res.put("_cmd", "logOK");
				res.put("id", String.valueOf(newUser.getUserId()));
				res.put("name", newUser.getName());

				ok = true;
			}
			
			// An exception occurred while logging the user in
			catch (LoginException le)
			{
				this.trace("Could not login user: " + nick);

				res.put("_cmd", "logKO");
				res.put("err", le.getMessage());
			}
		}
		
		// The user name is not among the valid ones
		else
		{
			res.put("_cmd", "logKO");
			res.put("err", "Sorry, your user name was not accepted.");
		}
		
		// Prepare the list of recipients, in this case we only one.
		LinkedList ll = new LinkedList();
		ll.add(chan);

		// Send login response
		sendResponse(res, -1, null, ll);	

		// Send room list
		if (ok)
			helper.sendRoomList(chan);
	}
}

First we get the three parameters in the event object: nickname, password and socket channel. It is useful to remark that at this point the client attempting the login is still seen as simple socket connection, not a User yet. The client will be promoted as User only after a successful login.

We then proceed by simply checking if the wanted user name is among those considered valid in our validNames list. If this is the case we proceed by logging in the user calling the canLogin() method from the ExtensionHelper class, which might throw a checked exception (LoginException).

Upon successful login we will send a logOK command to the client together with the user id and name. If anything goes wrong we will instead send a logKO command together with an additional parameter (err) containing the error description.

Now we can see how simple it is to handle the server response on the client side. (Actionscript 3)

public function onExtensionResponse(evt:SFSEvent):void
{
	var params:Object = evt.params.dataObj
	var cmd:String = params._cmd
	
	if (cmd == "logOK")
	{
		sfs.myUserId = params.id
		sfs.myUserName = params.name

		trace("Great, login was successful!")
	}
	else if (cmd == "logKO")
	{
		trace("Oops, login failed. Reason: " + params.err)
	}
}

Recipe #2:

The following example is slight variation on the theme of the previous one. Instead of using a simple list of names we will use a connection to a database and perform a full credential check against it.

Setting up a database connection is pretty straightforward as it is all done declaratively in the Zone setup, in your config.xml file. For more details on how to setup a database connection please refer to chapters 6.3 and 6.4 of the documentation.

ExtensionHelper helper;
Zone currentZone;
DbManager dbManager;

public void init()
{
	helper = ExtensionHelper.instance();
	currentZone = helper.getZone(this.getOwnerZone);
	dbManager = currentZone.dbManager;
}
	
public void handleInternalEvent(InternalEventObject evt)
{
	if (evt.getEventName().equals(InternalEventObject.EVENT_LOGIN))
	{
		boolean ok = false;
		User newUser = null;
		
		// Prepare a response object for the client
		ActionscriptObject response = new ActionscriptObject();
		
		// get the user nickname and password
		String nick = ieo.getParam("nick");
		String pass = ieo.getParam("pass");
		
		// get the user socket channel
		SocketChannel chan = (SocketChannel) ieo.getObject("chan");
		
		// validate user name
		ok = checkCredentials(nick, pass);
		
		if (ok)
		{
			try
			{
				// Attempt to login the user in the system
				newUser = helper.canLogin(nick, pass, chan, currentZone);

				res.put("_cmd", "logOK");
				res.put("id", String.valueOf(newUser.getUserId()));
				res.put("name", newUser.getName());

				ok = true;
			}
			
			// An exception occurred while logging the user in
			catch (LoginException le)
			{
				this.trace("Could not login user: " + nick);

				res.put("_cmd", "logKO");
				res.put("err", le.getMessage());
			}
		}
		
		// Invalid credentials
		else
		{
			res.put("_cmd", "logKO");
			res.put("err", "Sorry, invalid credentials.");
		}
		
		// Prepare the list of recipients, in this case we only one.
		LinkedList ll = new LinkedList();
		ll.add(chan);

		// Send login response
		sendResponse(res, -1, null, ll);	

		// Send room list
		if (ok)
			helper.sendRoomList(chan);
	}
}

// Here we execute the check on the database
boolean checkCredentials(String name, String pass)
{
	boolean result = false;
	
	// Escape quotes on passed data
	name = SmartFoxLib.escapeQuotes(name);
	pass = SmartFoxLib.escapeQuotes(pass);
	
	// SQL statement to execute
	String sql = "SELECT id,name,pass FROM registered_users WHERE" + 
				"name='" + name "'" + 
				"AND pass='" + pass + "'";
	
	// Execute the SQL statement
	ArrayList queryRes = dbManager.executeQuery(sql);
		
	// If record was found exist...
	if (queryRes != null && queryRes.size() > 0)
	{
		result = true;
	}	
		
	return result;
}

As you can see the code is pretty much the same of Recipe #1 and we have added a new method, checkCredentials(), which takes care of the database details. In the first lines we make sure to escape the data passed by the user in order to avoid problems with the SQL syntax. We then build the query and run it via the dbManager object.

The client code for handling the server response is the same as in Recipe #1.

NOTE: Sometimes it is useful to store the database id of the user for later usage in your extension.
It's usually not a good idea to transmit this id on the client side. It would be much better to keep it on the server side and access it from the User object when needed. In order to do so each User object exposes a properties field of type java.util.Map that can be used to store any data related to the current session of the user.

This code stores the database id in the User object:

	userObj.properties.put("dbId", dbId);

This code retrieves the database id in the User object:

	int dbId = (Integer) userObj.properties.get("dbId");