Introduction

My previous post provided a walk-through for using the Twitter streaming API from the command line, but tweets can be more flexibly obtained and processed using an API for accessing Twitter using your programming language of choice. In this tutorial, I walk-through basic setup and some simple uses of the twitter4j library with Scala. Much of what I show here should be useful for those using other JVM languages like Clojure and Java. If you haven’t gone through the previous tutorial, have a look now before going on as this tutorial covers much of the same material but using twitter4j rather than HTTP requests.



I’ll introduce code, bit by bit, for accessing the Twitter data in different ways. If you get lost with what should go where, all of the code necessary to run the commands is available in this github gist, so you can compare to that as you move through the tutorial.

Getting set up

An easy way to use the twitter4j library in the context of a tutorial like this is for the reader to set up a new SBT project, declare it as a dependency, and then compile and run code within SBT. (See my tutorial on using Jerkson for processing JSON with Scala for another example of this.) This sorts out the process of obtaining external libraries and setting up the classpath so that they are available. Follow the instructions in this section to do so.

$ mkdir ~/twitter4j-tutorial $ cd ~/twitter4j-tutorial/ $ wget http://repo.typesafe.com/typesafe/ivy-releases/org.scala-sbt/sbt-launch/0.12.2/sbt-launch.jar

Now, save the following as the file ~/twitter4j-tutorial/build.sbt. Be aware that it is important to keep the empty lines between each of the declarations.

name := 'twitter4j-tutorial' version := '0.1.0 ' scalaVersion := '2.10.0' libraryDependencies += 'org.twitter4j' % 'twitter4j-stream' % '3.0.3'

Then save the following as the file ~/twitter4j-tutorial/build.

java -Xms512M -Xmx1536M -Xss1M -XX:+CMSClassUnloadingEnabled -XX:MaxPermSize=384M -jar `dirname $0`/sbt-launch.jar '$@'

Make that file executable and run it, which will show SBT doing a bunch of work and then leave you with the SBT prompt. At the SBT prompt, invoke the update command.

$ cd ~/twitter4j-tutorial $ chmod a+x build $ ./build [info] Set current project to twitter4j-tutorial (in build file:/Users/jbaldrid/twitter4j-tutorial/) > update [info] Updating {file:/Users/jbaldrid/twitter4j-tutorial/}default-570731... [info] Resolving org.twitter4j#twitter4j-core;3.0.3 ... [info] Done updating. [success] Total time: 1 s, completed Feb 8, 2013 12:55:41 PM

To test whether you have access to twitter4j now, go to the SBT console and import the classes from the main twitter4j package.

> console [info] Starting scala interpreter... [info] Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_37). Type in expressions to have them evaluated. Type :help for more information. scala> import twitter4j._ import twitter4j._

If nothing further is output, then you are all set (exit the console using CTRL-D). If things are amiss (or if you are running in the default Scala REPL), you’ll instead see something like the following.

scala> import twitter4j._ <console>:7: error: not found: value twitter4j import twitter4j._ ^

If this is what you got, try to follow the instructions above again to make sure that your setup is exactly as above (check the versions, etc). If you just want to see some examples of using twitter4j as an API and are happy adding its jars by hand to your classpath or are using an IDE like Eclipse, then it is unnecessary to do the SBT setup — just read on and adapt the examples as necessary.

Write, compile and run a simple main method

To set the stage for how we’ll run programs in this tutorial, let’s create a simple main method and ensure it can be run in SBT. Do the following:

$ mkdir -p ~/twitter4j-tutorial/src/main/scala/

Next, save the following code as ~/twitter4j-tutorial/src/main/scala/TwitterStream.scala.

package bcomposes.twitter object StatusStreamer { def main(args: Array[String]) { println('hi') } }

Next, at the SBT prompt for the twitter4j-tutorial project, use the run-main command as follows.

> run-main bcomposes.twitter.StatusStreamer [info] Compiling 1 Scala source to /Users/jbaldrid/twitter4j-tutorial/target/scala-2.10/classes... [info] Running bcomposes.twitter.StatusStreamer hi [success] Total time: 2 s, completed Feb 8, 2013 1:36:32 PM

SBT compiles the code, and then runs it. This is a generally handy way of running code with all the dependencies available without having to worry about explicitly handling the classpath. In what comes below, we’ll flesh out that main method so that it does more interesting work.

Setting up authorization

When using the Twitter streaming API to access tweets via HTTP requests, you must supply your Twitter username and password. To use twitter4j, you also must provide authentication details; however, for this you need to set up OAuth authentication. This is straightforward:

Go to https://dev.twitter.com/apps and click on the button that says “Create a new application” (of course, you’ll need to log in with your Twitter username and password in order to do this) Fill in the name, description and website fields. Don’t worry too much about this: put in whatever you like for the name and description (e.g. “My example application” and “Tutorial app for me”). For the website, give the URL of your Twitter account if you don’t have anything better to use. A new screen will come up for your application. Click on the button at the bottom that says “Create my access token”. Click on the “OAuth tool” tab and you’ll see four fields for authentication which you need in order to use twitter4j to access tweets and other information from Twitter: Consumer key, Consumer secret, Access token, and Access token secret.

Based on these authorization details, you now need to create a twitter4j.conf.Configuration object that will allow twitter4j to access the Twitter API on your behalf. This can be done in a number of different ways, including environment variables, properties files, and in code. To keep it as simple as possible for this tutorial, we’ll go with the latter option.

Add the following object after the definition of StatusStreamer, providing your details rather than the descriptions given below.

object Util { val config = new twitter4j.conf.ConfigurationBuilder() .setOAuthConsumerKey('[your consumer key here]') .setOAuthConsumerSecret('[your consumer secret here]') .setOAuthAccessToken('[your access token here]') .setOAuthAccessTokenSecret('[your access token secret here]') .build }

You should of course be careful not to let your details be known to others, so make sure that this code stays on your machine. When you start developing for real, you’ll use other means to get the authorization information injected into your application.

Pulling tweets from the sample stream

In the previous tutorial, the most basic sort of access was to get a random sample of tweets from https://stream.twitter.com/1/statuses/sample.json, so let’s use twitter4j to do the same.

To do this, we are going to create a TwitterStream instance that gives us an authorized connection to the Twitter API. To see all the methods associated with the TwitterStream class, see the API documentation for TwitterStream. A TwitterStream instance is able to get tweets (and other information) and then provide them to any listeners that have registered with it. So, in order to do something useful with the tweets, you need to implement the StatusListener interface and connect it to the TwitterStream.

Before showing the code for creating and using the stream, let’s create a StatusListener that will perform a simple action based on tweets streaming in. Add the following code to the Util object created earlier.

def simpleStatusListener = new StatusListener() { def onStatus(status: Status) { println(status.getText) } def onDeletionNotice(statusDeletionNotice: StatusDeletionNotice) {} def onTrackLimitationNotice(numberOfLimitedStatuses: Int) {} def onException(ex: Exception) { ex.printStackTrace } def onScrubGeo(arg0: Long, arg1: Long) {} def onStallWarning(warning: StallWarning) {} }

This method creates objects that implement StatusListener (though it only does something useful for the onStatus method and otherwise ignores all other events sent to it). Clearly, what it is going to do is take a Twitter status (which is all of the information associated with a tweet, including author, retweets, geographic coordinates, etc) and output the text of the status—i.e., what we usually think of as a “tweet”.

The following code puts it all together. We create a TwitterStream object by using the TwitterStreamFactory and the configuration, add a simpleStatusListener to the stream, and then call the sample method of TwitterStream to start receiving tweets. If that were the last line of the program, it would just keep receiving tweets until the process was killed. Here, I’ve added a 2 second sleep so that we can see some tweets, then clean up the connection and shut it down cleanly. (We could let it run indefinitely, but then to kill the process, we would need to use CTRL-C, which will kill not only that process, but also the process that is running SBT.)

object StatusStreamer { def main(args: Array[String]) { val twitterStream = new TwitterStreamFactory(Util.config).getInstance twitterStream.addListener(Util.simpleStatusListener) twitterStream.sample Thread.sleep(2000) twitterStream.cleanUp twitterStream.shutdown } }

To run this code, simply put in the same run-main command in SBT as before.

> run-main bcomposes.twitter.StatusStreamer

You should see tweets stream by for a couple of seconds and then you’ll be returned to the SBT prompt.

Pulling tweets with specific properties

As with the HTTP streaming, it’s easy to use twitter4j to follow a particular set of users, particular search terms, or tweets produced within certain geographic regions. All that is required is creating appropriate FilterQuery objects and then using the filter method of TwitterStream rather than the sample method.

FilterQuery has several constructors, one of which allows an Array of Long values to be provided, each of which is the id of a Twitter user who is to be followed by the stream. (See the previous tutorial to see one easy way to get the id of a user based on their username.)

object FollowIdsStreamer { def main(args: Array[String]) { val twitterStream = new TwitterStreamFactory(Util.config).getInstance twitterStream.addListener(Util.simpleStatusListener) twitterStream.filter(new FilterQuery(Array(1344951,5988062,807095,3108351))) Thread.sleep(10000) twitterStream.cleanUp twitterStream.shutdown } }

These are the IDs for Wired Magazine (@wired), The Economist (@theeconomist), the New York Times (@nytimes), and the Wall Street Journal (@wsj). Add the code to TwitterStream.scala and then run it in SBT. Note that I’ve made the program sleep for 10 seconds in order to give more time for tweets to arrive (since these are just four accounts and will have varying activity). If you are not seeing anything show up, increase the sleep time.

> run-main bcomposes.twitter.FollowIdsStreamer

To track tweets that contain particular terms, create a FilterQuery with the default constructor and then call the track method with an Array of strings that contains the query terms you are interested in. The object below does this, and uses the args Array as the container for the query terms.

object SearchStreamer { def main(args: Array[String]) { val twitterStream = new TwitterStreamFactory(Util.config).getInstance twitterStream.addListener(Util.simpleStatusListener) twitterStream.filter(new FilterQuery().track(args)) Thread.sleep(10000) twitterStream.cleanUp twitterStream.shutdown } }

With things set up this way, you can track arbitrary queries by specifying them on the command line.

> run-main bcomposes.twitter.SearchStreamer scala > run-main bcomposes.twitter.SearchStreamer scala python java > run-main bcomposes.twitter.SearchStreamer 'sentiment analysis' 'machine learning' 'text analytics'

If the search terms are not particularly common, you’ll need to increase the sleep time.

To filter by location, again create a FilterQuery with the default constructor, but then use the locations method, with an Array[Array[Double]] argument — basically an Array of two-element Arrays, each of which contains the latitude and longitude of a corner of a bounding box. Here’s an example that creates bounding box for Austin and uses it.

object AustinStreamer { def main(args: Array[String]) { val twitterStream = new TwitterStreamFactory(Util.config).getInstance twitterStream.addListener(Util.simpleStatusListener) val austinBox = Array(Array(-97.8,30.25),Array(-97.65,30.35)) twitterStream.filter(new FilterQuery().locations(austinBox)) Thread.sleep(10000) twitterStream.cleanUp twitterStream.shutdown } }

To make things more flexible, we can take the bounding box information on the command line, convert the Strings into Doubles and pair them up.

object LocationStreamer { def main(args: Array[String]) { val boundingBoxes = args.map(_.toDouble).grouped(2).toArray val twitterStream = new TwitterStreamFactory(Util.config).getInstance twitterStream.addListener(Util.simpleStatusListener) twitterStream.filter(new FilterQuery().locations(boundingBoxes)) Thread.sleep(10000) twitterStream.cleanUp twitterStream.shutdown } }

We can call LocationStreamer with multiple bounding boxes, e.g. as follows for Austin, San Francisco, and New York City.

> run-main bcomposes.twitter.LocationStreamer -97.8 30.25 -97.65 30.35 -122.75 36.8 -121.75 37.8 -74 40 -73 41

Conclusion

This shows the start of how you can use twitter4j with Scala for streaming. It also supports programmatic access to the actions that any Twitter user can take, including posting messages, retweeting, following, and more. I’ll cover that in a later tutorial. Also, some examples of using twitter4j will start showing up soon in the tshrldu project.



Reference: Using twitter4j with Scala to access streaming tweets from our JCG partner Jason Baldridge at the Bcomposes blog.