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Concatenate a list of paths to a variable - to pass to "java -classpath ..." in CMD batch script

I am trying to port a simple shell script starting a Java program to a CMD batch script for Windows:
#echo on
set REPO="C:\Users\user1\.m2\repository"
set VERSION=9.3.9.v20160517
"C:\Program Files\Java\jdk1.8.0_66\bin\java.exe" -classpath C:\Users\user1\slova\WebSockets\target\classes;%REPO%\javax\servlet\javax.servlet-api\3.1.0\javax.servlet-api-3.1.0.jar;%REPO%\org\eclipse\jetty\websocket\websocket-server\%VERSION%\websocket-server-%VERSION%.jar;%REPO%\org\eclipse\jetty\websocket\websocket-common\%VERSION%\websocket-common-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-io\%VERSION%\jetty-io-%VERSION%.jar;%REPO%\org\eclipse\jetty\websocket\websocket-client\%VERSION%\websocket-client-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-servlet\%VERSION%\jetty-servlet-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-security\%VERSION%\jetty-security-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-server\%VERSION%\jetty-server-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-http\%VERSION%\jetty-http-%VERSION%.jar;%REPO%\org\eclipse\jetty\websocket\websocket-servlet\%VERSION%\websocket-servlet-%VERSION%.jar;%REPO%\org\eclipse\jetty\websocket\websocket-api\%VERSION%\websocket-api-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-util-ajax\%VERSION%\jetty-util-ajax-%VERSION%.jar;%REPO%\org\eclipse\jetty\jetty-util\%VERSION%\jetty-util-%VERSION%.jar;%REPO%\org\postgresql\postgresql\9.4.1208.jre7\postgresql-9.4.1208.jre7.jar de.afarber.websockets.MyHandler
As you can see (if you scroll the above code to the right) there is a longer list of file paths following the java -classpath string.
Is it please possible to list the paths each on a separate line - and then concatenate that list by the means of CMD shell to a variable (adding semicolon ; inbetween)?
That way I could better maintain my batch file (easier to edit in editor) and would finally just call java -classpath %CPATHS% de.afarber.websockets.MyHandler
UPDATE:
If all JAR-files would be located in the same dir, I could have used the new Java 8 wildcard syntax java -classpath "\that\dir\*" de.afarber.websockets.MyHandler - but that wasn't the case here.

You can use a variable in this form:
set MYCLASSPATH=C:\Users\user1\slova\WebSockets\target\classes
set MYCLASSPATH=%MYCLASSPATH%;%REPO%\javax\servlet\javax.servlet-api\3.1.0\javax.servlet-api-3.1.0.jar
...
"C:\Program Files\Java\jdk1.8.0_66\bin\java.exe" -classpath %MYCLASSPATH% ...

Change $JAVA_HOME in python script

I've tried to make a python script to switch between 32bit and 64 bit java but for some reason
os.system('export JAVA_HOME=/usr/java/path')
os.system('export PATH=$JAVA_HOME/bin:$PATH')
does nothing, but manually it works. How can I fix this? (BTW, this is running on a Linux system.)

The export line will set an environment variable for the shell in which it's executed and all its sub-shells. But what's happening here is that Python creates a new shell, executes the line to set the environment variable, and then the shell terminates. That means the environment variable is no longer in force. In fact, the JAVA_HOME environment variable you set in the first line isn't even in force for the second line when that gets executed, because that's in its own shell that also terminates immediately!
The way round it is to run a whole shell script that sets the environment variable and then launches Java:
#!/bin/bash
JAVA_HOME=/usr/java/path
PATH=$JAVA_HOME/bin:$PATH
java ...

Environment variables are local to each process. If you want to make a permanent change then you can follow the official java PATH instructions. They recommend adding the export variable command to your .bashrc file.
In ~/.bashrc:
export JAVA_HOME=/usr/java/path
export PATH=$JAVA_HOME/bin:$PATH

You can chain the commands together - jdk set + script execution like this:
setJdk4Gradle = 'export JAVA_HOME=/home/jdkPath && export PATH=$JAVA_HOME/bin:$PATH'
os.system(setJdk4Gradle + ' && executeSomething')

Ubuntu now able to set java path

I have installed oracle jdk in /usr/lib/jvm/ and i have setted up path in etc/environment as
JAVA_HOME=/usr/lib/jvm/jdk1.7.0_51
PATH=$PATH:$JAVA_HOME/bin
But still when i am running javac, I am getting following error. The program 'javac' can be found in the following packages:
* default-jdk
* ecj
* gcj-4.6-jdk
* gcj-4.7-jdk
* openjdk-7-jdk
* openjdk-6-jdk
It means javac is not installed or java path has not setted properly, however i am able to see javac,java,jps and other programs in my /usr/lib/jvm/jdk1.7.0_51. I have searched enough about it but still not able to get solution of this problem.

The file /etc/environment is not a file executed by the shell (like a shell script); you cannot use $SOMETHING references in this file. Variables are not substituted in this file. So,
JAVA_HOME=/usr/lib/jvm/jdk1.7.0_51
PATH=$PATH:$JAVA_HOME/bin
the second line will not work like this. You have to put the exact path in.
JAVA_HOME=/usr/lib/jvm/jdk1.7.0_51
PATH=...:/usr/lib/jvm/jdk1.7.0_51/bin

The javac binary (and probably other java binaries) is/are not in your user's $PATH environment variable. There are several ways you can address this:
Add /usr/lib/jvm/jdk1.7.0_51/bin to your user's $PATH
environment variable. You can do this by adding a line similar to
the following in your user's .bash_profile:
export PATH=${PATH}:/usr/lib/jvm/jdk1.7.0_51/bin
You'll have to restart your terminal session for it to take effect.
Create symbolic links to the java binaries from some directory
that's already part of your path (such as /usr/bin)
sudo ln -s /usr/lib/jvm/jdk1.7.0_51/bin/java /usr/bin/
sudo ln-s /usr/lib/jvm/jdk1.7.0_51/bin/javac /usr/bin/
BTW: There are several other java executables in /usr/lib/jvm/jdk1.7.0_51/bin. see the symlink commands for java and javac above. You should run similar command for any other executables you may want to use.
Use the fully qualified path directly on the command line:
$ /usr/lib/jvm/jdk1.7.0_51/bin/javac

https://help.ubuntu.com/community/Java
have you tried this page? Its where I go when I need Java info. You may not have the one you installed set as default.

Could it be that you did not refresh the shell after change in path variable?
if you echo $PATH are the changes present?

Unable to execute java program from crontab job of other user

I am unable to run a crontab job , under a different user.(For e.g sudo -u someuser crontab -e)
It runs absolutely fine under my user profile.
I know what is the issue, but cannot find the resolution for it.
The issue is , when i configure this crontab job for other user, crontab is not able to find java ,as a result even simple java -version is not working.
Below is my script.
#!/bin/bash
export JAVA_HOME=/usr/jdk/jdk1.6.0_31
export PATH=/usr/local/bin:/bin:/usr/bin:/opt/dell/srvadmin/bin:/home/VishalS/bin
echo "JAVA_HOME is: " $JAVA_HOME >> log.out
echo "PATH is: " $PATH >> log.out
which java >> log.out
/usr/bin/java -version >> log.out
/usr/jdk/jdk1.6.0_31/bin/java -version >> log.out
output of above script :
JAVA_HOME is: /usr/jdk/jdk1.6.0_31
PATH is: /usr/local/bin:/bin:/usr/bin:/opt/dell/srvadmin/bin:/home/VishalS/bin
/usr/bin/java
so obviously, the below lines did not work.
/usr/bin/java -version >> log.out
/usr/jdk/jdk1.6.0_31/bin/java -version >> log.out
Could somebody please help me here? I do not understand why even after setting jdk path crontab does not executes java -version ?

Try setting the paths in the other users crontab directly. See 'man 5 crontab'.

The only that comes to my mind is that, the java command might not have the Executable permission to the user you are trying to execute it from.
So use chmod to give necessary permissions to execute.

Crontab(5) runs without ENV, so you need to source an environment (you are building the JAVA_HOME and PATH, but crontab gives you (almost) nothing. notice that the output of "which java" did not appear in your log file.
build an environment script you can source for your crontab script(s), ". path/to/env.sh"
Put full paths on all programs executed in shell scripts etc. You cannot rely upon environment in cron
run "which which", did you get /usr/bin/which? then put that in your script.
we often omit paths from scripts for convenience, but give paths in scripts run from crontab
does the java run when logged in as the other user?

Thanks everyone for your helpful comments.
However the actual fix which worked in my-case , was mix of steps as mentioned below :-
1. Setup Sun JDK path under root's user profile.(earlier open jdk was setup)
2. Gave permission to logs folder where logs were being written.(earlier the permission were not correctly set)
3. Tweaked my cronjob(i think there was an extra space there)

Do commands run from current directory in a shell script?

In a bash shell script I tried these two versions:
java -jar abc.jar&
and
CMD="java -jar abc.jar&"
$CMD
The first verison works, and the second version complains that abc.jar cannot be found. Why?

Commands do run from current directory in a shell script.
This is why the first command in your test script worked.
The second command may not work because either java isn't in your ${PATH} or abc.jar isn't in your ${CLASSPATH}. You could echo these environment variables or set +x to debug your bash script.

Bash (and others) won't let you do backgrounding (&) within the value of a variable (nor will they let you do redirection that way or pipelines). You should avoid putting commands into variables. See BashFAQ/050 for some additional information.
What is the actual error message you're getting? I bet it's something like "abc.jar& not found" (note the ampersand) because the ampersand is seen as a character in the filename.
Also, the current directory for the script is the directory that it is run from - not the directory in which it resides. You should be explicit about the directory that you want to have your file in.
java -jar /path/to/abc.jar&