[java] How to set JAVA_HOME for multiple Tomcat instances?

I have 2 Java Web Projects. One runs on JDK 1.5 and the other runs on JDK 1.6. I want to run both of them on the same computer, but the JAVA_HOME environment variable can only have one value. I want to set JAVA_HOME for each Tomcat server.

Also, note that there shouldn't be any space after =:

set JAVA_HOME=C:\Program Files\Java\jdk1.6.0_27

For Debian distro we can override the setting via defaults

/etc/default/tomcat6

Set the JAVA_HOME pointing to the java version you want.

JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64

Just a note...

If you add that code to setclasspath.bat or setclasspath.sh, it will actually be used by all of Tomcat's scripts you could run, rather than just Catalina.

The method for setting the variable is as the other's have described.

I think this is a best practice (You may be have many Tomcat instance in same computer, you want per Tomcat instance use other Java Runtime Environment):

This is manual inside file: catalina.sh

#   JRE_HOME        Must point at your Java Runtime installation.
#                   Defaults to JAVA_HOME if empty. If JRE_HOME and JAVA_HOME
#                   are both set, JRE_HOME is used.

In UNIX I had this problem, I edited catalina.sh manually and entered

export JAVA_HOME=/usr/lib/jvm/java-6-sun-1.6.0.24
echo "Using JAVA_HOME:       $JAVA_HOME"

as the first 2 lines. I tried setting the JAVA_HOME in /etc/profile but it did not help.

This worked finally.

If you are a Windows user, put the content below in a setenv.bat file that you must create in Tomcat bin directory.

set JAVA_HOME=C:\Program Files\Java\jdk1.6.x

If you are a Linux user, put the content below in a setenv.sh file that you must create in Tomcat bin directory.

JAVA_HOME=/usr/java/jdk1.6.x

place a setenv.sh in the the bin directory with

JAVA_HOME=/usr/java/jdk1.6.0_43/
JRE_HOME=/usr/java/jdk1.6.0_43/jre

or an other version your running.

I had the same problem my OS is windows 8 and I am using Tomcat 8, I just edited the setclasspath.bat file in bin folder and set JAVA_HOME and JRE_HOME like this...

@echo off
...
...
set "JRE_HOME=%ProgramFiles%\Java\jre8"
set "JAVA_HOME=%ProgramFiles%\Java\jdk1.7.0_03"
...
...

and it works fine for me now......

Linux based Tomcat6 should have /etc/tomcat6/tomcat6.conf

# System-wide configuration file for tomcat6 services
# This will be sourced by tomcat6 and any secondary service
# Values will be overridden by service-specific configuration
# files in /etc/sysconfig
#
# Use this one to change default values for all services
# Change the service specific ones to affect only one service
# (see, for instance, /etc/sysconfig/tomcat6)
#

# Where your java installation lives
#JAVA_HOME="/usr/lib/jvm/java-1.5.0"

# Where your tomcat installation lives
CATALINA_BASE="/usr/share/tomcat6"
...

One thing that you could do would be to modify the catalina.sh (Unix based) or the catalina.bat (windows based).

Within each of the scripts you can set certain variables which only processes created under the shell will inherit. So for catalina.sh, use the following line:

export JAVA_HOME="intented java home"

And for windows use

set JAVA_HOME="intented java home"

You can add setenv.sh in the the bin directory with:

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

and it will dynamically change when you update your packages.