What JDK switcher is
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 use openjdk7 jdk_switcher home oraclejdk7 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:
Sun JDK 6 will be EOL in November 2012 and is not supported. Ubuntu 12.04 and next Fedora release both will use OpenJDK 7 by default. Time to upgrade, JDK 7 is backwards compatible and packed with improvements.
How does it work?
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.
Why was this tool necessary?
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.
License & Copyright
Copyright (c) 2012-2016 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.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.