Compile Time Dependency Injection with MacWire

A lot of examples that has to do with Compile Time Dependency Injection using the Play! Framework 2.4 just deal with the simple cases. How to get it running or how to inject a service into a controller.

But I wanted the full picture. What if I want to use Play 2.4 in combination with MacWire. And configure a PostgreSQL database with Slick 3.1 and Play managing the database evolutions.

Run it locally

Running the whole setup is easy (I hope ;-)). Prerequisites for running this project is that you have sbt and 'Docker Machine' installed.

In the root of the project there is a runlocal.sh script that will build a docker container, start a docker container and will run the Play applcation through sbt run.

If docker and sbt have downloaded the internet ;-), you can access the application through http://localhost:9000.

Run it on Heroku

I use the following 'Config Vars' on Heroku.

 SBT_CLEAN=true
 PLAY_CONF_FILE=application.conf
 APPLICATION_SECRET=<sbt playGenerateSecret>

Structure

Postgres, Slick and Evolutions

The dependencies in the build.sbt needed to use Slick, (Database) Evolutions for a PostgreSQL database are as follows:

libraryDependencies ++= Seq(
  evolutions,
  "com.typesafe.play" %% "play-slick" % "1.1.1",
  "com.typesafe.play" %% "play-slick-evolutions" % "1.1.1",
  "com.typesafe.slick" %% "slick" % "3.1.0",
  "org.postgresql" % "postgresql" % "9.4-1206-jdbc42",

'evolutions' is the configured Play import of the module 'play-jdbc-evolutions'. This is followed by the integration library for Slick within Play and the use of Evolutions in combination with Slick. Last but not least, Slick itself and the JDBC-driver.

The configuration in the src/main/resources/application.conf configures the use of evolutions, Slick for PostgreSQL.

play.evolutions.db.default.autoApply=true
slick.dbs.default.driver= "slick.driver.PostgresDriver$"
slick.dbs.default.db.driver="org.postgresql.Driver"
slick.dbs.default.db.url=${?JDBC_DATABASE_URL}

play.evolutions.db.default.autoApply=true enables automatically applying database-changes. The other three properties are needed to access the database with Slick. More than one database is possible, in this case we use the default database name 'default'.

Links

See the following documentation, links that I used

• [Generic documentation on Play 2.4 Compile Time dependency injection] (https://www.playframework.com/documentation/2.4.x/ScalaCompileTimeDependencyInjection)
• A reply from Nicolae Namolovan had a link to Gist which brought the solution for my problem with automatically applying the database evolutions.

Problems

My problem with applying database evolutions

I tried for an hour to get the database evolutions to be applied. I thought everything was ok. Even compared my setup with another project. In the end I realized I had left one, VERY important, element out in the SQL-file. If you leave that comment out, you can have a beautifully crafted SQL-file, but Play will do nothing with it ;-(.

# --- !Ups

...

# --- !Downs

...

I know, it is stated perfectly in the Play Documentation. But hey, are we always looking at the documentation ;-).

Slug size problems

I got errors on the slug size:

-----> Compressing... 
 !   Compiled slug size: 304.7MB is too large (max is 300MB).

The build log said

-----> Scala app detected

but this was wrong. Comparing it to another application, I could find no differences between the Heroku configuration. Looking at the [activation of the Play framework](-----> Scala app detected) for Heroku I read the following "Heroku Play framework support will be applied to applications that match: */conf/application.conf". As I use the standard SBT layout the application.conf resides in src/main/resources. So the application is not recognized as Play 2 Application, and therefore does not clean up a.o. the ivy2 cache.

Adding a dummy file (conf/application.conf) will trigger the scala buildpack to see this project as a Play 2.4 application,

Created an issue to a get a more flexible way for Play 2.4 detection with.