Java on Scalingo

Java is officially supported on Scalingo

Versions

  • 1.7
  • 1.8
  • 9
  • 10
  • 11

Frameworks

Most frameworks should work on the platform, the only condition is to listen on the port defined by the environment variable PORT

  • Spring Boot: You can find custom information about this framework at the following page

Languages Using the JVM

Even though the Java Virtual Machine (JVM) was initially designed to execute program developed with Java, a lot of new languages have been developed to be executed on it. Most of them should work on Scalingo. Here are examples of such languages known to work on Scalingo:

  • Scala: see the specific documentation page here.
  • Groovy: see the specific documentation page here.
  • Clojure: see the specific documentation page here.
  • Kotlin: see the sample deployed here.

Deployment

It uses Maven 3.3.9 to build your application and OpenJDK 1.8 to run it (by default).

Example usage:

$ ls
Procfile  pom.xml  src

$ scalingo create my-app

$ git push scalingo master
...
-----> Java app detected
-----> Installing OpenJDK 1.8... done
-----> Installing Maven 3.3.9... done
-----> Installing settings.xml... done
-----> executing /app/tmp/repo.git/.cache/.maven/bin/mvn -B -Duser.home=/tmp/build_19z6l4hp57wqm -Dmaven.repo.local=/app/tmp/repo.git/.cache/.m2/repository -s /app/tmp/repo.git/.cache/.m2/settings.xml -DskipTests=true clean install
       [INFO] Scanning for projects...
       [INFO]
       [INFO] ------------------------------------------------------------------------
       [INFO] Building readmeTest 1.0-SNAPSHOT
       [INFO] ------------------------------------------------------------------------
...

The buildpack will detect your app as Java if it has the file pom.xml in the root. It will use Maven to execute the build defined by your pom.xml and download your dependencies.

If your build results in a .war file you need to add a small dependency to your project in order to execute it. Just follow the guide.

The .m2 folder (local maven repository) will be cached between builds for faster dependency resolution. However neither the mvn executable nor the .m2 folder will be available in your slug at runtime.

Configuration

Choose a JDK

Create a system.properties file in the root of your project directory and set java.runtime.version=1.7 (or any of the Java supported version).

Example:

$ ls
Procfile pom.xml src

$ echo "java.runtime.version=11" > system.properties

$ git add system.properties && git commit -m "Java 7"

$ git push scalingo master
...
-----> Java app detected
-----> Installing OpenJDK 11... done
...

Choose a Maven Version

The system.properties file also allows for maven.version entry (regardless of whether you specify a java.runtime.version entry). For example:

java.runtime.version=9
maven.version=3.2.5

Supported versions of Maven are:

  • 3.0.5
  • 3.1.1
  • 3.2.5
  • 3.3.9

You can request new versions of Maven by submitting a pull request to the Java buildpack against the vendor/maven/sources.txt file.

Customize Maven

There are two environment variables that can be used to customize the Maven execution:

  • MAVEN_CUSTOM_GOALS: set to clean install by default
  • MAVEN_CUSTOM_OPTS: set to -DskipTests=true by default

These variables can be set like this:

$ scalingo env-set MAVEN_CUSTOM_GOALS="clean package"
$ scalingo env-set MAVEN_CUSTOM_OPTS="--update-snapshots -DskipTests=true"

Other options are available for defining custom a settings.xml file.

Add a custom CA to Java Keychain

You may need to add one or multiple custom certificates to your JDK’s Keychain. You need to download Scalingo default JDK cacerts, then add the custom certificates you’d like to add with the following command:

keytool -import -keystore cacerts -file custom.cer

Then create the following directory in your application .jdk-overlay/jre/lib/security/ and move the cacerts keystore file to it. Add it to your repository, and that’s it! Your custom CAs will be taken into account.

Buildpack

More information at https://github.com/Scalingo/java-buildpack.


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