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https://github.com/michaelklishin/jdk_switcher

A yet another Ubuntu/Debian-specific tool that makes switching between multiple JDK versions a one liner
https://github.com/michaelklishin/jdk_switcher

debian java openjdk ubuntu version-manager

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A yet another Ubuntu/Debian-specific tool that makes switching between multiple JDK versions a one liner

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README 

        
# 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](https://github.com/travis-ci/travis-cookbooks) but

may be useful in other environments, too.



## Usage



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:



``` bash

. ./jdk_switcher.sh



jdk_switcher home oraclejdk10



jdk_switcher  use openjdk7



jdk_switcher home ibmjdk8

```



### Commands



 * `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.



### JDK aliases



Supported aliases are:



 * `oraclejdk10`

 * `oraclejdk8`

 * `oraclejdk7`

 * `openjdk7`

 * `openjdk6`

 * `ibmjdk8`



## How Does it Work?



The switcher uses [update-java-alternatives](http://manpages.ubuntu.com/manpages/hardy/man8/update-java-alternatives.8.html) (see also [this intro](http://wiki.debian.org/Java/#Java_and_Debian)) 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.



## 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



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.



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.