Using Twitter4J's UserStreamListener with EJB - ejb

Question

Looking around StackOverflow, I see this answer to a similar problem - according to the Twitter4J documentation, TwitterStream#addListener takes a callback function. I have naively written my class as follows:
#Stateless
#LocalBean
public class TwitterListenerThread implements Runnable {
private TwitterStream twitterStream;
public TwitterListenerThread(){}
#EJB private TwitterDispatcher dispatcher;
#Override
public void run() {
ConfigurationBuilder cb = new ConfigurationBuilder();
cb.setDebugEnabled(true)
.setJSONStoreEnabled(true)
.setOAuthConsumerKey(Properties.getProperty("twitter_OAuthConsumerKey"))
.setOAuthConsumerSecret(Properties.getProperty("twitter_OAuthConsumerSecret"))
.setOAuthAccessToken(Properties.getProperty("twitter_OAuthAccessToken"))
.setOAuthAccessTokenSecret(Properties.getProperty("twitter_OAuthAccessTokenSecret"));
twitterStream = new TwitterStreamFactory(cb.build()).getInstance();
UserStreamListener listener = new UserStreamListener() {
#Override
public void onStatus(Status status) {
dispatcher.dispatch(status);
}
// Standard code
};
twitterStream.addListener(listener);
// Listen for all user activity
String user = Properties.getProperty("twitter-userid");
String[] users = {user};
twitterStream.user(users);
}
}
Now, on my colleague's PC this soon fails with an attempt to invoke when container is undeployed on the dispatcher.dispatch(status); line. I understand the reason as being due to the Twitter4J threading model not playing well with the JavaEE EJB model, but I cannot work out what to do based on the answer presented in the linked answer - how would I use a Message-Driven Bean to listen in to the Twitter stream?

Answer 1

After a little thinking, I worked out that the solution offered was to write a separate application that used just Java SE code to feed, using non-annotated code, a JMS queue with tweets, and then in my main application use a Message-Driven Bean to listen to the queue.
However, I was not satisfied with that work-around, so I searched a little more, and found Issue TFJ-285, Allow for alternative implementations of Dispatcher classes:
Now it is possible to introduce your own dispatcher implementation.
It can be Quartz based, it can be MDB based, and it can be EJB-timer based.
By default, Twitter4J still uses traditional and transient thread based dispatcher.
Implement a class implementing twtitter4j.internal.async.Dispatcher interface
put the class in the classpath
set -Dtwitter4j.async.dispatcherImpl to locate your dispatcher implementation
This is the default implementation on GitHub, so one could replace the:
private final ExecutorService executorService;
with a:
private final ManagedExecutorService executorService;
And, in theory, Bob's your uncle. If I ever get this working, I shall post the code here.