The Scala language extends the Java language with improvements to language features and syntax. While it supports javascript and native runtime environments the primary runtime environment is the JRE, developing for the JRE requires a JDK install. Some options for installation follow.
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Install a standalone JDK.
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Managing multiple versions of the JDK can be done from terminals using SDKMAN!.
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When using IntelliJ IDEA you can use it to manage JDK installs from the settings dialogue.
Scala projects use sbt as a portable build tool that can be used standalone or with an IDE.
IntelliJ IDEA is a commercial IDE with free support for Scala, and free upgrades to its commercial edition for academic users.
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Install IntelliJ IDEA.
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Install the Scala language plugin.
https://www.jetbrains.com/help/idea/discover-intellij-idea-for-scala.html
This plugin requires IntelliJ, other Jetbrains IDEs are not supported. Community edition will enable debugging and syntax highlighting in the project and support for Scala, while Ultimate edition will additionally enable full support for Play framework, HTML, CSS, SCSS, Javascript and Scala.js.
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Optionally, install a JDK managed by IntelliJ.
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Set the project SDK to the installed JDK.
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The scala plugin will install a managed version of sbt, you can optionally reconfigure the project to use a standalone installation by changing the sbt launcher location setting.
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Import the project folder from GitHub as a sbt project.
https://www.jetbrains.com/help/idea/manage-projects-hosted-on-github.html#clone-from-GitHub
https://www.jetbrains.com/help/idea/sbt-support.html#import_sbt
Note: Future versions of sbt and the Scala plugin, will switch to importing as a BSP project. The first releases claiming BSP support required standalone sbt installs (fixed) and did not correctly regenerate project structure definitions on changes to
build.sbt. -
When you open the project folder in IntelliJ it will need to build the project structure definitions from the build.sbt definition. Any changes to
build.sbtrequire a new build of the project structure.https://www.jetbrains.com/help/idea/sbt-support.html#manage_sbt_projects
The project build, structure, and dependencies are defined in build.sbt, any Scala IDE can interact with sbt to build and run the project, and generate structure definitions and dependency lists. The following alternatives can be used:
- ScalaIDE
ScalaIDE is built on Eclipse a popular open source IDE. The project can be imported without changes as a sbt project. There are some IntelliJ config files in the repository that define code style choices and version control system choice. It is untested whether the Eclipse Interoperability plugin can export these settings. The primary concern of the plugin is project structure and module definitions which should not be exported as these are generated from
build.sbt. - Metals
Metals is a language server, this allows any text editor to communicate with it and access language support. This allows plugins to be developed that are compatible with any text editor that implements the language server protocol. Metals can be used with Visual Studio Code, Eclipse, Vim, Emacs, Sublime Text.
- Launch the sbt shell
- command line: Run the
sbtcommand. - IntelliJ: Open the sbt shell tool, usually accessible via a tool tab at the bottom of window.
https://www.jetbrains.com/help/idea/sbt-support.html#sbt_shell
- command line: Run the
- After the sbt shell has loaded use the
runcommand.https://www.playframework.com/documentation/2.8.x/PlayConsole
- Browse to http://localhost:9001.
https://www.playframework.com/documentation/2.8.x/NewApplication#Scala-template
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Exceptions will be printed to both the sbt shell and shown as static error pages in the browser.
https://www.playframework.com/documentation/2.8.x/ScalaErrorHandling
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To debug the play application, debug mode needs to be enabled for the sbt shell in IntelliJ. The shell can then be relaunched as a debug session.
https://www.jetbrains.com/help/idea/run-debug-and-test-scala.html#debug_scala_code
https://www.playframework.com/documentation/2.8.x/sbtDebugging#Debugging-your-build
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Use a browser's developer tools to debug javascript and scala.js sources. Firefox Developer Edition is recommended,
F12key opens the dev tools in most browsers. -
The Play application log is saved to server/logs/application.log.
https://www.playframework.com/documentation/2.8.x/Anatomy#The-Play-application-layout