Tagged: scala

Apache Spark: Convert CSV to RDD

Below is a simple Spark / Scala example describing how to convert a CSV file to an RDD and perform some simple filtering. This example transforms each line in the CSV to a Map with form header-name -> data-value. Each map key corresponds to a header name, and each data value corresponds the value of that key the specific line. This particular example also assumes that the header information is...

How to use the Play WS library in a standalone Scala app

The Play WS library makes it possible to execute HTTP requests and process the response asynchronously. It provides an awesome API that is incredibly easy to use. (I’ve provided a few simple WS examples toward the end of this post.) Prior to the release of Play 2.4 (the current 2.4 release is the M2 milestone release), it was possible to utilize the WS API in a standalone Play app, however...

Testing with Specs2 and Play ReactiveMongo

Are you building a Scala PlayFramework application with ReactiveMongo? Are you testing your application with Specs2? Are some of your tests failing with the dreaded, “Can’t get ClosableLazy value after it has been closed”? Do those same tests pass, if they are run individually? If so, this post is for you! Note: A full stack trace for the dreaded ClosableLazy can be found in the Appendix of this post. In...

Scala Futures by example

What is a Future? A Future is essentially a placeholder object that is created for a result that does not yet exist. Scala Futures are asynchronous and non-blocking (by default) and are thus often handled with callbacks. Hmm. What about ‘callback hell’? Scala Futures are monadic in nature and can be combined, composed, sequenced, and executed concurrently. All of this can be accomplished with Scala in a very simple, yet...