It’s time to explore Scala. I still enjoy Java programming, and that’s still what I do for a living. But I have to admit that Scala is intriguing. Plus, it’s good to learn new languages every so often. And as they say, Java is more than a language; it’s also a platform and an ecosystem, one that Scala fits very well into.
I’ve gone through different books and tutorials, but the best way to learn a language is to come up with a task and figure out how to do it. I’ve decided that while I’m learning Scala, I’ll also learn the Play! framework. My task will be a microservice whose purpose is to authenticate users. Although my current employer doesn’t use Scala (at least not directly, although we do use Kafka, Akka, and other technologies written in Scala) my plan is to write a service that could be used by the company. That way I won’t be tempted to cut corners.
As I develop this project, I’ll post the solutions to any issues I encounter along the way. I figure there are probably enough Scala noobs out there who might encounter the same problems. I also figure that some of these issues might be very elementary to developers who are more experienced with Play! and Scala. In that vein, any corrections or suggestions are most welcome!
Maven Repositories (and the Oracle driver)
I started a few days ago, and hit two issues rather quickly. The first stems from my company’s use of Oracle as its RDBMS; that’s where we store user credentials. So of course I would need to read from Oracle in order to authenticate users.
As I understand it, Play! makes use of SBT (the Simple Build Tool), which is developed by Typesafe, and is used to manage Play! projects (and other Scala-based frameworks). SBT is analogous to Maven for pure Java projects. In fact, SBT makes use of Ivy for dependency management; Ivy, in turn, makes use of Maven repositories.
So I figured I’d need to pull the Oracle JDBC driver from Maven Central. Play! projects are created with a build.sbt file in the project’s root directory, and that’s where dependencies are listed. We use ojdbc6 (the Oracle JDBC driver for Java 6), so our POM entry looks like this:
To add that to build.sbt, it would look like this:
libraryDependencies += "com.oracle" %% "ojdbc6" % "220.127.116.11"
I added that to build.sbt, and was confronted with errors stating that that dependency couldn’t be resolved. Turns out that due to licensing reasons, Oracle does not allow its JDBC driver in any public repos. So the solution is to simply download the JAR file from Oracle, create a lib/ directory in the Play! project’s root, and add the JAR there.
Admittedly, that was as much an issue of the ojdbc6 driver than with Play! itself, but I thought it worth documenting here.
Artifactory (or Nexus, if you prefer)
Next up was the issue of artifacts that my company produces. Much of our code is encapsulated in common JAR files and, of course, hosted in our own internal (Artifactory) repository. Specifically, the domain class that I would be pulling from the database contains, among other fields, and enum called Type (yes, I know… that name was not my doing!) which was located in a commons module. I could’ve created a Scala Enumeration for my project, or just skipped the field, but I wanted to demonstrate the interoperability between new Scala projects and our existing Java code.
So I’d have to point SBT to the correct location to find the commons module. I found bits and pieces online on how to do it; here’s the solution that I ultimately pieced together:
(1) SBT had already create a ~/.sbt/0.13/ directory for me. In there, I created a plugins/ subdirectory and with there a credentials.sbt file with these contents:
(2) Within the existing ~/.ivy2/ directory, created a .credentials file with these contents:
(3) Add the repository location in ~/.sbt.repositories like so:
(4) Added the following line in ~/.sbtconfig to tell SBT where to find the credentials:
I’m not sure why we need both step 1 and 4, but both seem to be required.
Once I restarted my Play! application (this was one case where hot-deployment didn’t seem to work) I was able to use the commons module in my Play! app.