This is a yet another Ubuntu/Debian-specific script that switches between multiple JDK versions (including those that may not have been installed via apt).

It is meant to be used in the travis-ci.org CI environment but may be useful in other environments, too.

Install one or more JDKs that register themselves with the update-java-alternatives tools by installing a .jinfo file under /usr/lib/jvm.

Then source jdk_switcher.sh in the repository root and use the jdk_switcher function it two arguments, a command and the JDK to use:

. ./jdk_switcher.sh

jdk_switcher home oraclejdk10

jdk_switcher  use openjdk7

jdk_switcher home ibmjdk8

• use: switches active JDK (updates PATH alternatives and exports JAVA_HOME)
• home: prints JAVA_HOME value for the specified JDK. Does not change anything in the environment.

Supported aliases are:

• oraclejdk10
• oraclejdk8
• oraclejdk7
• openjdk7
• openjdk6
• ibmjdk8

The switcher uses update-java-alternatives (see also this intro) under the hood to update /etc/alternatives/* symlinks for java, javac, javap and other JDK tools. As such, the switcher itself primary handles aliasing of JDKs (update-java-alternatives aliases are too hard to remember) and updating JAVA_HOME value.

JAVA_HOME changes is the reason why jdk_switcher is implemented as a function.

JAVA_HOME updates is the key reason for it to exist: update-java-alternatives and related Debian tools in general do a great job of managing alternatives but won't touch or even define JAVA_HOME. Even though most JVM ecosystem tools (from Leiningen to Elastic Search, HBase and Cassandra) will try hard to detect JAVA_HOME value but unfortunately, Maven 3 does it in a way that is heavily biased towards OpenJDK 6.

For travis-ci.org to support multiple JDKs for Clojure, Groovy, Java, Scala and JRuby, it is crucially important that all the tools we provision will use the JDK version specified for a build. We cannot let Maven always use OpenJDK 6.

MIT LICENSE

Copyright (c) 2012-2019 Michael S. Klishin and Travis CI Development Team

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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