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
.jinfo file under
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
PATHalternatives and exports
JAVA_HOMEvalue for the specified JDK. Does not change anything in the environment.
Supported aliases are:
The switcher uses update-java-alternatives (see also this intro) under the hood to update
/etc/alternatives/* symlinks for
javap and other JDK tools. As such, the switcher itself primary handles aliasing of
update-java-alternatives aliases are too hard to remember) and updating
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.
Copyright (c) 2012-2019 Michael S. Klishin and Travis CI Development Team
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