Adventures In Scala - Part 1: play-scala-intro

Learning Scala Part 1 - play-scala-intro

So, as of writing this, my background is primarily C#. This post is the first part of a series which will document my transition into all things Scala. I will be writing a step by step on creating a simple web stack.

My Setup

I’ll be using Linux Mint 17.3, but most flavours of debian should work for any of my bash.

PostgreSQL 9.3.11
IntelliJ IDEA, targeting Open JDK 1.8_72
Scala 2.11 with SBT, SSP, HOCON
Play! 2.5.1 Framework (Using IntelliJ’s plugin)
Slick

Install our software packages

$ apt-get update
$ apt-get install postgresql postgresql-contrib openjdk-8-jdk
$ wget https://www.jetbrains.com/idea/download/download-thanks.html?platform=linux
$ sudo tar -xvzf ideaIU-2016.1.1.tar.gz -C /usr/share/intellij/
$ cd /usr/share/intellij
$ sudo bash ./idea.sh

Note: If you’re missing the openjdk-8-jdk package, add it to your repo list with add-apt-repository ppa:openjdk-r/ppa

Set up our PostgreSQL DB

By default, postgres creates a user named ‘postgres’, we want to login to them, and start up our postgres console in the default ‘postgres’ database.

$ sudo su postgres
$ psql -d postgres -U postgres

Create a user and db. Connect to it, and set new user’s permissions to rw.

postgres=# CREATE USER scalaplay WITH PASSWORD '<Password>'
postgres=# CREATE DATABASE scalaplaydb;
postgres=# \c scalaplaydb
postgres=# REVOKE ALL ON DATABASE scalaplaydb FROM PUBLIC;
postgres=# REVOKE ALL ON SCHEMA public FROM PUBLIC;
postgres=# GRANT CONNECT ON DATABASE scalaplaydb TO scalaPlay;
postgres=# GRANT SELECT,UPDATE,INSERT,DELETE ON ALL TABLES IN SCHEMA public TO scalaplay;
postgres=# GRANT SELECT,UPDATE ON ALL SEQUENCES IN SCHEMA public TO scalaplay;
postgres=# GRANT USAGE ON SCHEMA public TO scalaplay;

If you want to have new tables with privileges already granted for previous users, run this

postgres=# ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT,UPDATE,INSERT,DELETE ON TABLES TO scalaplay;
postgres=# ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT,UPDATE ON  SEQUENCES TO scalaplay;

Some handy user check commands if you’re not sure what users can do what:

postgres=# \du            ; Displays user roles with attributes/membership
postgres=# \l             ; Displays db list, with access privileges
postgres=# \z             ; Displays access privileges to schemas

Let’s make some sample tables to interact with later

postgres=# CREATE TABLE <name>(...)
...
postgres=# \q
postgres=# exit

Play 2.X Framework Template

Grab a sample play framework project template to load into IntelliJ

$ wget https://www.lightbend.com/activator/template/bundle/play-scala-intro.zip
$ unzip play-scala-intro -d ~/play/
$ sudo ./$HOME/play/play-scala-intro/bin/activator ui

Select the ‘scala-play-intro’ template, and create it. This may take a bit of downloading Open the project in IntelliJ…

Potential Issues

If you get a java.io.FileNotFoundException: (Permission denied), you may want to sudo chown <user>:<user> -R ~/scala-play-intro
If you get a java.lang.UnsupportedClassVersionError: ... Unsupported major.minor version 52.0 or similar, ensure you are targeting the project to Java 1.8 through the IDE’s project settings with (File -> Project Structure). Also, you may want to make sure you set the java alternatives using:

$ sudo update-alternatives --config java
$ sudo update-alternatives --config javac
$ java -version