Is it possible to specify the JVM to use when you call "java jar jar_name.jar" . I have two JVM installed on my machine. I can not change JAVA_HOME as it may break code that is all ready running.
Kind Regards
Stephen
Yes - just explicitly provide the path to java.exe. For instance:
c:\Users\Jon\Test>"c:\Program Files\java\jdk1.6.0_03\bin\java.exe" -version
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
Java HotSpot(TM) Client VM (build 1.6.0_03-b05, mixed mode, sharing)
c:\Users\Jon\Test>"c:\Program Files\java\jdk1.6.0_12\bin\java.exe" -version
java version "1.6.0_12"
Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
Java HotSpot(TM) Client VM (build 11.2-b01, mixed mode, sharing)
The easiest way to do this for a running command shell is something like:
set PATH=c:\Program Files\Java\jdk1.6.0_03\bin;%PATH%
For example, here's a complete session showing my default JVM, then the change to the path, then the new one:
c:\Users\Jon\Test>java -version
java version "1.6.0_12"
Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
Java HotSpot(TM) Client VM (build 11.2-b01, mixed mode, sharing)
c:\Users\Jon\Test>set PATH=c:\Program Files\Java\jdk1.6.0_03\bin;%PATH%
c:\Users\Jon\Test>java -version
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
Java HotSpot(TM) Client VM (build 1.6.0_03-b05, mixed mode, sharing)
This won't change programs which explicitly use JAVA_HOME though.
Note that if you get the wrong directory in the path - including one that doesn't exist - you won't get any errors, it will effectively just be ignored.
You should be able to do this via the command line arguments, assuming these are Sun VMs installed using the usual Windows InstallShield mechanisms with the JVM finder EXE in system32.
Type java -help for the options. In particular, see:
-version:<value>
require the specified version to run
-jre-restrict-search | -jre-no-restrict-search
include/exclude user private JREs in the version search
yes I often need to have 3 or more JVM's installed. For example, I've noticed that sometimes the JRE is slightly different to the JDK version of the JRE.
My go to solution on Windows for a bit of 'packaging' is something like this:
#echo off
setlocal
#rem _________________________
#rem
#set JAVA_HOME=b:\lang\java\jdk\v1.6\u45\x64\jre
#rem
#set JAVA_EXE=%JAVA_HOME%\bin\java
#set VER=test
#set WRK=%~d0%~p0%VER%
#rem
#pushd %WRK%
cd
#echo.
#echo %JAVA_EXE% -jar %WRK%\openmrs-standalone.jar
%JAVA_EXE% -jar %WRK%\openmrs-standalone.jar
#rem
#rem _________________________
popd
endlocal
#exit /b
I think it is straightforward. The main thing is the setlocal and endlocal give your app a "personal environment" for what ever it does -- even if there's other programs to run.
If you have 2 installations of the JVM.
Place the version upfront.
Linux : export PATH=/usr/lib/jvm/java-8-oracle/bin:$PATH
This eliminates the ambiguity.
Related
I want to switch between jdks below on Linux (using update-java-alternatives):
java-1.11.0-openjdk-amd64 1111 /usr/lib/jvm/java-1.11.0-openjdk-amd64
java-16-oracle 1091 /usr/lib/jvm/java-16-oracle
java-1.8.0-openjdk-amd64 1081 /usr/lib/jvm/java-1.8.0-openjdk-amd64
What should I set my JAVA_HOME to? Is it possible for update-java-alternatives to set JAVA_HOME?
I would suggest to use something like https://sdkman.io/ - it allows you to download and easy switch between various versions of JDK.
Example of the command to switch between the envs and the result:
➜ echo $JAVA_HOME
/home/pdys/.sdkman/candidates/java/current
~
➜ java -version
openjdk version "16.0.1" 2021-04-20
OpenJDK Runtime Environment AdoptOpenJDK-16.0.1+9 (build 16.0.1+9)
OpenJDK 64-Bit Server VM AdoptOpenJDK-16.0.1+9 (build 16.0.1+9, mixed mode, sharing)
~
➜ sdk use java 8.0.242.hs-adpt
Using java version 8.0.242.hs-adpt in this shell.
~
➜ java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_242-b08)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.242-b08, mixed mode)
~
➜ echo $JAVA_HOME
/home/pdys/.sdkman/candidates/java/8.0.242.hs-adpt
What should I set my JAVA_HOME to?
Respectively:
export JAVA_HOME=/usr/lib/jvm/java-1.11.0-openjdk-amd64
export JAVA_HOME=/usr/lib/jvm/java-16-oracle
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64
Is it possible for update-java-alternatives to set JAVA_HOME?
No. It isn't.
The purpose of update-java-alternatives is to create / maintain the symlinks in /usr/bin etcetera which determine what the "global" settings are. The JAVA_HOME environment variable is for per-user / per-script (or per-session) configuration. They are orthogonal.
I guess you could write a shell function that sets JAVA_HOME to (say) the Java installation that corresponds to whatever /usr/bin/java currently resolves to.
I am currently with installing and integrating a couple of software on Linux, and I'm very new to Linux. One of the software refuses to run and instructs me to properly set $JAVA_HOME. But I have set $JAVA_HOME! However, when I check the $JAVA_HOME and java -version tests to see if I have done it correctly, it only produces the correct answer when I'm logged in as opc. The permissions of the software I am trying to install is oracle. Do I need to set $JAVA_HOME again when I'm logged in as oracle? And why?
[opc#mydir ~]$ $JAVA_HOME
-bash: /u01/jdk-11.0.3/: Is a directory
[opc#mydir ~]$ java -version
java version "11.0.3" 2019-04-16 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.3+12-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.3+12-LTS, mixed mode)
[opc#mydir ~]$ sudo su oracle
[oracle#mydir opc]$ $JAVA_HOME
[oracle#mydir opc]$ java -version
bash: java: command not found
Environment variables (such as $JAVA_HOME) are set per process. For shells, you'd usually have some initialization script (like .bashrc) that sets all the relevant variables for the current session. You should copy the initialization of $JAVA_HOME you have in the opc user to the oracle user too.
I am aware this might look duplicated, but I don't seem to find the answer that I am seeking (perhaps is too trivial).
I just downloaded java from the oracle site and I read this:
$java -version
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)
Then I added this to my .bash_profile file:
# Java
export JAVA_HOME="`/usr/libexec/java_home -v 1.8`"
so that:
$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home
So far so good.
Now when I type:
$ which java
/usr/bin/Java
Which I think is the default installation (?, I really have no experience in Java)
At this stage, I don't know if I have to simlink:
sudo ln -s /Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home/bin/java /usr/bin
or if the simlink was establish during the java installation. I am going to start installing a series of things that depend on java, so I would like to make sure I understand this before moving on.
Thanks!
What you've done will work. From my system:
$ /usr/bin/java -version
java version "1.8.0_92"
Java(TM) SE Runtime Environment (build 1.8.0_92-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.92-b14, mixed mode)
It uses the java_home command you used, which depends on the Java part of the System Preferences application. So if somehow you have the "wrong" version in use, you can fix it there. But by default, it seems in my experience to use the latest version (man java_home doesn't really say).
I have a appilcation that needs Java 32bit on my Debian 64bit server. Is running fine now with this in the .profile or in the SH file.
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_25/
export LD_LIBRARY_PATH=.:$JAVA_HOME/jre/lib/i386/server:$JAVA_HOME/jre/lib/i386/client:/usr/local/lib
However, when I to start it over screen it simply don't load the Java path and the LD lib path.
Anyone has a idea how to solve this problem?
Please, give me the results the next commands in your console
java -version
and
echo $JAVA_HOME
echo $LD_LIBRARY_PATH
Do you have this in you environments variables?
env | grep JAVA
In my case I have this
user:$ java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)
user:$ echo $JAVA_HOME
/opt/jdk/jdk1.8.0_25
user:$ env | grep JAVA
JAVA_HOME=/opt/jdk/jdk1.8.0_25
Please see these 3 commands and their outcomes in MacOS:
Korays-MacBook-Pro:~ koraytugay$ /usr/libexec/java_home
/Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home
Korays-MacBook-Pro:~ koraytugay$ java -version
java version "1.7.0_55"
Java(TM) SE Runtime Environment (build 1.7.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)
Korays-MacBook-Pro:~ koraytugay$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.7.0_55.jdk/Contents/Home
Why does the first one return 1.8? What exactly is /libexec/java_home ?
Koray,
As per the Oracle docs...
JAVA_HOME is just an environment variable used to trigger the 'java' found in your PATH to use a different JDK image. Unfortunately, not all 'java' startup scripts obey this env variable. It's also used by many java tool startup scripts to determine what 'java' to run, bypassing the 'java' found in the PATH setting. Setting this variable during a JDK build is a bad idea, don't do it.
I use Eclipse myself, and don't have a JAVA_HOME env variable defined, here is my output running the same commands.
brandon#brandons-mbp ~
$ /usr/libexec/java_home
/Library/Java/JavaVirtualMachines/jdk1.8.0_05.jdk/Contents/Home
brandon#brandons-mbp ~
$ java -version
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)
brandon#brandons-mbp ~
$ echo $JAVA_HOME
Not sure why you have two different versions but did you try updating your JDK recently? Maybe when you upgraded it failed to launch a script to update your $JAVA_HOME.
Here's the instructions for installing JDK and setting JAVA_HOME on *nix based OSes.
Let me know if that helps I can help you dig deeper if need be.