Step 1. Get a Twitter account and create a Twitter application from http://twitter.com/apps (don’t forget to check in browser and enter a  valid callback url.

Step 2.  Download twitter4J add the library (in my case twitter4j-core-2.1.1-SNAPSHOT.jar) to project and update classpath

Step 3. Create a web application (I assume you have the Google plugin for Eclipse )

Step 4. Add the following servlets and update your web.xml. First servlet will handle login part. It will create a RequestToken which will create the magical aggrements between the consumer(your application) and provider(twitter). First servlet save the  token and secret token since we will need them later.

String token = requestToken.getToken();
String tokenSecret = requestToken.getTokenSecret();

• Home servlet
• Login Servlet

Step 5. You forget to update web.xml didn’t you, update the web.xml

Step 6.  Enable session by adding

    <sessions-enabled>true</sessions-enabled>

to appengine-web.xml.

You can see my version from http://90.latest.denemekaya.appspot.com/login

ps. don’t forget to set the callback in Twittter to the url of the servlet for callback.

Links:

• http://www.pakzilla.com/2009/10/03/tutorial-java-based-twitter-app-on-google-app-engine/
• Explain the same procedure with Grails — http://blogs.bytecode.com.au/glen/2009/12/08/log-into-your-grails-app-using-your-twitter-credentials.html

Memcache provides convenience to store a frequent query in memory, so that you don’t have to make the same execution over and over again. For the iPhone application I build (Fragman), I build a GAE/J backend for managing movie names, IMDB URLs, thumb images, video files, etc. It interacts with the Obj-c code via calls encoded in JSON.

Since the categories are updated so frequently (new trailer, top 250 , soap opera trailers), every time the user starts the application from her iPhone, the corresponding categories Id(key) lists are  created which includes all the aspects mentioned above,

what I see, after people start to use the application that, most of the time, the application got stuck with the time constraint of GAE and this causes inconvenience, so I decided to hold the category lists’s JSON in memory. Following is the code ,

this is the servlet for creating the JSON which is called after say upcoming movie list is changed. This servlet updates the memcached list

        List keyList = new ArrayList();
	static Cache cache;
	static
	{
		try
		{
			CacheFactory cacheFactory =

CacheManager.getInstance().getCacheFactory();
			cache = cacheFactory.createCache(

Collections.emptyMap());
		}
		catch (CacheException e)
		{
			// ...
		}
		//.....
                public void doGet(HttpServletRequest request,

HttpServletResponse response) throws ServletException, IOException

	        {
                       //................
                       if(cache.containsKey(mode))
		       {
			     cache.remove(mode);
		       }
		       cache.put(mode, keyList);
	        }

                //........

          }

And this is the servlet that fetch the Fragman beans from the datastore with the given keys (key list is got from the memecached list)

          keyList = (List)cache.get(mode);

By doing this, I reduce the time that the servlet that creates the JSON takes.