What is the correct target for the JAVA_HOME envri

Question

In Windows, JAVA_HOME must point to the JDK installation folder (so that JAVA_HOME/bin contains all executables and JAVA_HOME/libs contains all default jar libraries).

If I download Sun's JDK bundle and installs it in Linux, it is the same procedure.

However, I need to use Kubuntu's default OpenJDK package. The problem is that all executables are placed in /usr/bin. But the jars are placed in /usr/share/java. Since they are not under the same JAVA_HOME folder I'm having trouble with Grails and maybe there will be trouble with other applications that expect the standard Java structure.

1. If I use:

   JAVA_HOME=/usr
   

   All applications and scripts that want to use any Java executable can use the standard procedure call $JAVA_HOME/bin/executable. However, since the jars are in a different place, they are not always found (example: in grails I'm getting ClassDefNotFound for native2ascii).

2. On the other hand, if I use:

   JAVA_HOME=/usr/share/java
   

   None of the Java executables (java, javac, etc.) can be found.

So, what is the correct way of handling the JAVA_HOME variable in a Debian-based Linux?

Thanks for your help, Luis

Answer 1

Try setting the JAVA_LIB variable also.

Answer 2

I've discovered similar problems with the openjdk-6-jre and openjdk-6-jre-headless packages in Ubuntu.

My problem was solved by purging the openjdk-6-jre and openjdk-6-jre-headless packages and re-installing. The alternatives are only updated on a fresh install of the openjdk-6-jre and openjdk-6-jre-headless packages.

Below is a sample of installing after purging:

aptitude purge openjdk-6-jre openjdk-6-jre-headless # to ensure no configuration exists
aptitude install --without-recommends openjdk-6-jre # Installing without some extras
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
The following NEW packages will be installed:
  ca-certificates-java{a} java-common{a} libavahi-client3{a} libavahi-common-data{a} libavahi-common3{a} libcups2{a} libflac8{a} libgif4{a} libnspr4-0d{a} libnss3-1d{a} libogg0{a} libpulse0{a} libsndfile1{a} libvorbis0a{a} libvorbisenc2{a} libxi6{a} libxtst6{a}
  openjdk-6-jre openjdk-6-jre-headless{a} openjdk-6-jre-lib{a} tzdata-java{a}
The following packages are RECOMMENDED but will NOT be installed:
  icedtea-6-jre-cacao icedtea-netx ttf-dejavu-extra
0 packages upgraded, 21 newly installed, 0 to remove and 119 not upgraded.
Need to get 0B/34.5MB of archives. After unpacking 97.6MB will be used.
Do you want to continue? [Y/n/?]
Writing extended state information... Done
Selecting previously deselected package openjdk-6-jre-lib.
(Reading database ... 62267 files and directories currently installed.)
Unpacking openjdk-6-jre-lib (from .../openjdk-6-jre-lib_6b24-1.11.5-0ubuntu1~10.04.2_all.deb) ...
...
Processing triggers for man-db ...
Setting up tzdata-java (2012e-0ubuntu0.10.04) ...
...
Setting up openjdk-6-jre-headless (6b24-1.11.5-0ubuntu1~10.04.2) ...
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/java to provide /usr/bin/java (java) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/keytool to provide /usr/bin/keytool (keytool) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/pack200 to provide /usr/bin/pack200 (pack200) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/rmid to provide /usr/bin/rmid (rmid) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/rmiregistry to provide /usr/bin/rmiregistry (rmiregistry) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/unpack200 to provide /usr/bin/unpack200 (unpack200) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/orbd to provide /usr/bin/orbd (orbd) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/servertool to provide /usr/bin/servertool (servertool) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/tnameserv to provide /usr/bin/tnameserv (tnameserv) in auto mode.
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/lib/jexec to provide /usr/bin/jexec (jexec) in auto mode.
Setting up openjdk-6-jre (6b24-1.11.5-0ubuntu1~10.04.2) ...
update-alternatives: using /usr/lib/jvm/java-6-openjdk/jre/bin/policytool to provide /usr/bin/policytool (policytool) in auto mode.
...

You can see above that update-alternatives is run to set up links for the various Java binaries.

After this install, there are also links in /usr/bin, links in /etc/alternatives, and files for each binary in /var/lib/dpkg/alternatives.

ls -l /usr/bin/java /etc/alternatives/java /var/lib/dpkg/alternatives/java
lrwxrwxrwx 1 root root  40 2013-01-16 14:44 /etc/alternatives/java -> /usr/lib/jvm/java-6-openjdk/jre/bin/java
lrwxrwxrwx 1 root root  22 2013-01-16 14:44 /usr/bin/java -> /etc/alternatives/java
-rw-r--r-- 1 root root 158 2013-01-16 14:44 /var/lib/dpkg/alternatives/java

Let's contast this with installing without purging.

aptitude remove openjdk-6-jre
aptitude install --without-recommends openjdk-6-jre
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
The following NEW packages will be installed:
  ca-certificates-java{a} java-common{a} libavahi-client3{a} libavahi-common-data{a} libavahi-common3{a} libcups2{a} libflac8{a} libgif4{a} libnspr4-0d{a} libnss3-1d{a} libogg0{a} libpulse0{a} libsndfile1{a} libvorbis0a{a} libvorbisenc2{a} libxi6{a} libxtst6{a}
  openjdk-6-jre openjdk-6-jre-headless{a} openjdk-6-jre-lib{a} tzdata-java{a}
The following packages are RECOMMENDED but will NOT be installed:
  icedtea-6-jre-cacao icedtea-netx ttf-dejavu-extra
0 packages upgraded, 21 newly installed, 0 to remove and 119 not upgraded.
Need to get 0B/34.5MB of archives. After unpacking 97.6MB will be used.
Do you want to continue? [Y/n/?]
Writing extended state information... Done
Selecting previously deselected package openjdk-6-jre-lib.
(Reading database ... 62293 files and directories currently installed.)
Unpacking openjdk-6-jre-lib (from .../openjdk-6-jre-lib_6b24-1.11.5-0ubuntu1~10.04.2_all.deb) ...
...
Processing triggers for man-db ...
...
Setting up openjdk-6-jre-headless (6b24-1.11.5-0ubuntu1~10.04.2) ...

Setting up openjdk-6-jre (6b24-1.11.5-0ubuntu1~10.04.2) ...
...

As you see, update-alternatives is not triggered.

After this install, there are no files for the Java binaries in /var/lib/dpkg/alternatives, no links in /etc/alternatives, and no links in /usr/bin.

The removal of the files in /var/lib/dpkg/alternatives also breaks update-java-alternatives.

Answer 3

As an update for fedora user , alternatives set current java directory to /usr/java/default

so you have to set your JAVA_HOME to /usr/java/default to always have alternatives curent selection in your classpath

HTH !

Answer 4

Updated answer that will solve your problem and also just a general good how-to for installing Oracle Java 7 on Ubuntu can be found here: http://www.wikihow.com/Install-Oracle-Java-on-Ubuntu-Linux

Answer 5

What finally worked for me (Grails now works smoothly) is doing almost like Steve B. has pointed out:

JAVA_HOME=/usr/lib/jvm/default-java

This way if the user changes the default JDK for the system, JAVA_HOME still works.

default-java is a symlink to the current JVM.

Answer 6

If you use alternatives to manage multiple java versions, you can set the JAVA_HOME based on the symlinked java like this:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")