[jira] [Commented] (MNG-5756) Java home output in mvn -v is misleading

["Michael Osipov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MNG-5756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15068967#comment-15068967 ] 

Michael Osipov commented on MNG-5756:
-------------------------------------

Just a note: with Java 9 this will be completely irrelevant, see [http://openjdk.java.net/projects/jigsaw/talks/prepare-for-jdk9-j1-2015.pdf|slides] 29, 30. You won't see any difference.

> Java home output in mvn -v is misleading
> ----------------------------------------
>
>                 Key: MNG-5756
>                 URL: https://issues.apache.org/jira/browse/MNG-5756
>             Project: Maven
>          Issue Type: Improvement
>          Components: Command Line
>    Affects Versions: 3.2.5, 3.3.3
>         Environment: any
>            Reporter: Jarkko Rantavuori
>            Priority: Minor
>
> For example on my windows box, mvn -v prints the following:
> {code}
> Java home: C:\Program Files (x86)\Java\jdk1.7.0_51\jre
> {code}
> But my JAVA_HOME is actually
> {code}
> > echo %JAVA_HOME%
> C:\Program Files (x86)\Java\jdk1.7.0_51
> {code}
> In the source code, the line comes from:
> https://git-wip-us.apache.org/repos/asf?p=maven.git;a=blob;f=maven-embedder/src/main/java/org/apache/maven/cli/CLIReportingUtils.java#l63
> {code}
> version.append( "Java home: " ).append( System.getProperty( "java.home", "<unknown java home>" ) ).append( ls );
> {code}
> which is using property "java.home" to fetch java home. However, "java.home" property is not JAVA_HOME! This is explained in detail in here: http://javahowto.blogspot.fi/2006/05/javahome-vs-javahome.html
> To quote:
> {quote}
>     What's the difference between JAVA_HOME and java.home?
>     JAVA_HOME is the JDK install directory, e.g., C:\jdk5. It's meant to be set as an environment variable and referenced in Windows batch files or Unix scripts. I always have it in my Windows Control Panel and .tcsh files,along with other common environment variables. Some Java applications use the name jdk.home for this purpose, which I think is a better name. But JAVA_HOME has been used since the beginning and is now a convention.
>     java.home is the JRE install directory, e.g., C:\jdk5\jre, or C:\Program Files\Java\jre1.5.0_06. Unlike JAVA_HOME, I never seen java.home as an environment variable. java.home is a build-in Java system property, whose value is the JRE install directory. Since all Java system properties are also exposed as Ant build properties, you can also use $&lcub;java.home&rcub; in build files.
>     Would jre.home be a better name? Maybe, but I don't think Sun will change it.
> {quote}
> This is a source of constant confusion. Some stackoverflow threads to illustrate:
> http://stackoverflow.com/questions/15279586/java-home-in-maven
> http://stackoverflow.com/questions/17620531/maven-pointing-to-jre-instead-of-jdk
> The correct way to print JAVA_HOME would be to use System.getenv("JAVA_HOME"). Either that should be used or current output should be changed so it wouldn't be so misleading.



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