How to have managed servers on different java JDK versions - java-7

Question

I have multiple domains installed on a Windows Server 2008 R2 instance running WebLogic 12.1.2.
When I created the domains I set the runtime JDK to 1.7.
In each domain, I have an admin server (with no deployed applications) and 6-20 managed servers.
For the 2-10 managed servers that have a specific application deployed,
I want to change the JDK to 1.6.
How do I do this?
Note: we are trying to isolate a performance issue and want to know if the recent upgrade from 1.6 to 1.7 is causing issues. Once we know if it is, then we can try to find the code that 1.7 doesn't like. So we rebuilt (with 1.6) the one service application that has the issue and are re-running the (long running) tests to compare run times.

Answer 1

I tested this with Weblogic 12c today.
Update /u01/oracle/middleware/user_projects/domains/{DOMAIN_NAME}/bin/setDomainEnv.sh (Find setDomainEnv.sh under your {domain directory}/bin).
Change BEA_JAVA_HOME="" to BEA_JAVA_HOME="/u01/oracle/java/jdk1.8.0_51" (jdk1.8.0_51 is the new jdk home directory, your version may be different).
Update your managed server's "Server Start" configuration on the Weblogic admin console specifying the new Java Home:/u01/oracle/java/jdk1.8.0_51 and Java Vendor: Oracle.
Restart managed server.
ps -ef | grep {managed server name} from your *nix console to confirm the java version running your managed server.
Following these steps I could run other managed servers with the original jdk, while switching selected managed servers to run with jdk1.8.0_51.
Good luck!

Answer 2

I AM NOT SURE IF WLS 12.1.2 supports JDK1.6.
Go to your setDomainEnv.cmd file under DOMAIN_HOME/bin
BEA_JAVA_HOME="/path/to/jdk1.6"
export BEA_JAVA_HOME
SUN_JAVA_HOME="/path/to/jdk1.8"
export SUN_JAVA_HOME
if [ "${JAVA_VENDOR}" = "Oracle" ] ; then
JAVA_HOME="${BEA_JAVA_HOME}"
export JAVA_HOME
else
if [ "${JAVA_VENDOR}" = "Sun" ] ; then
JAVA_HOME="${SUN_JAVA_HOME}"
export JAVA_HOME
else
JAVA_VENDOR="Sun"
export JAVA_VENDOR
JAVA_HOME="${SUN_JAVA_HOME}"
export JAVA_HOME
fi
fi
Then go to your Admin Console, go to Managed_server > Configuration > Server Start
Set JAVA_HOME and JAVA_VENDOR as you defined in setDomainEnv.cmd
You may set as many JAVA_HOME as you want by defining JAVA_HOME and JAVA_VENDOR in setDomainEnv.cmd. I myself have 4 different JDKs configured to be used by the same domain.
You may check the current JDK version that the managed server is running on by using admin console:
Go to managed_server > Monitoring > General