How to Setup the JDK Correctly

[malcon lopez]

Hello,

Initially I installed the openjdk , but I found that My Web App does not run so that this openjdk version and some mistakes in the configuration, right now I have installed the jdk1.7.0_51 on my.
I also typed this on the ssh.

export PATH=/usr/lib/jvm/jdk1.7.0_51/bin:/usr/lib/jvm/jdk1.7.0_51/db/bin:$PATH
export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_51
export DERBY_HOME=/usr/lib/jvm/jdk1.7.0_51/db/bin

Everything's ok, however when I exit from the console and type the java -version still shows me

java version "1.6.0_27"
OpenJDK Runtime Environment (IcedTea6 1.12.6) (6b27-1.12.6-1~deb7u1)
OpenJDK Client VM (build 20.0-b12, mixed mode, sharing)

Not the latest one.

Could anyone help me to solve this problem. I will be happy

[Jeanne Boyarsky]

If you type this command, does it show your changes to the path? (I'm guessing it doesn't.)
echo $PATH

When you say you exit from the console, does that mean opening a new SSH connection or something else?

[Tim Holloway]

"export" doesn't promote the environment assignment to other command shells. It merely ensures that the assignment will be visible in the child shells your current shell spawns.

As long as you have JAVA_HOME set to the proper JDK in the shell that launches Tomcat, its value in other shells doesn't matter.

Although I don't have much use for IcedTea myself, so I do my exports for things like JAVA_HOME at a higher level. There are many places to do this. One is the profile of the user account that Tomcat is launched under. Another is the set of profiles used globally by the various shells and defined in the /etc directory.

[malcon lopez]

Jeanne Boyarsky wrote:If you type this command, does it show your changes to the path? (I'm guessing it doesn't.)
echo $PATH

When you say you exit from the console, does that mean opening a new SSH connection or something else?

Hi Jeanne ,

Thanks for your reply, I type this echo $PATH and prints "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/lib/jvm/java-1.6.0-openjdk-i386/bin
" it is still using the openjdk version not the Oracle JDK that it is located at /usr/share/java/jdk1.7.0_51

When you say you exit from the console, does that mean opening a new SSH connection or something else?
Just opening another SSH with the same IP of the server, it seems that does not save the path configuration and does not work my app web.

[Tim Holloway]

If you're using the catalina.sh control script that came with Tomcat, it executes Java as "$JAVA_HOME/bin/java". Your PATH settings should immaterial, since the path of the appropriate java runtime is fully qualified in the control script.

[malcon lopez]

Tim Holloway wrote:"export" doesn't promote the environment assignment to other command shells. It merely ensures that the assignment will be visible in the child shells your current shell spawns.

As long as you have JAVA_HOME set to the proper JDK in the shell that launches Tomcat, its value in other shells doesn't matter.

Although I don't have much use for IcedTea myself, so I do my exports for things like JAVA_HOME at a higher level. There are many places to do this. One is the profile of the user account that Tomcat is launched under. Another is the set of profiles used globally by the various shells and defined in the /etc directory.

I followed many tutorials and I don't know how to config it!

[Tim Holloway]

export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_51 
export CATALINA_HOME=/wherever/tomcat/is
$CATALINA_HOME/bin/catalina.sh start

There's also startup.sh and shutdown.sh (.bat) files in CATALINA_HOME/bin. I just happen to prefer invoking the master control script directly.

The JRE_HOME, CATALINA_BASE and other Tomcat environment variables will get their values as defaults based on JAVA_HOME and CATALINA_HOME, so those are the only 2 that count.

As I said before. Tomcat doesn't actually care what the PATH is set to, since it uses explicity command paths. I'm not sure about your DERBY_HOME setting. It's not a bad idea to create a $CATALINA_HOME/bin/setenv.sh file and put the export for DERBY_HOME there, though. You can also override Tomcat's JAVA_OPTS in setenv.sh if you want to override the default VM memory sizes and stuff.

[Anayonkar Shivalkar]

Hi malcon,

If I understand your requirement - you want to change default Java version on your system. If this is correct, and you've installed various Java versions (i.e. not copy-pasted installation directories), then below command might be helpful:

sudo update-alternatives --config java

[Tim Holloway]

I really hate the "alternatives" system. It's confusing and awkward.

What it's supposed to do, however, is allow substitution of competing implementations of various complex programs by effectively re-wiring the system resource locations on a per-user basis.

You don't need that to run Tomcat, since the third-party Java developer kits such as the one from Sun/Oracle are designed to be hosted in a single unzipped directory and Tomcat in particular can work just fine as long as you set JAVA_HOME to point to that directory.

Actually, I'm not sure "alternatives" handles the JDK. It may only support JREs. I'm not certain, since, as previously mentioned, I don't use it.

[Anayonkar Shivalkar]

To my knowledge, update-alternatives updates JDK as well.

I tried to change the version and new version is reflected in both below commands:

java -version
javac -version