How to use environment variable in CLASSPATH?

[Praveen Kumar Jayaram]

Hi,

Is there a way to use Java environment variable in classpath in the following manner?

java -Dtest.path="D:/testing" -cp ${test.path}/lib/test.jar

I understand we can use already declared system environment variables like Path in classpath. But I'm looking for the environment variable used by "-D" option.
Kindly let me know if this is possible.

[Jeff Verdegan]

http://docs.oracle.com/javase/6/docs/api/java/lang/System.html#getenv()
http://docs.oracle.com/javase/6/docs/api/java/lang/System.html#getenv(java.lang.String)

[Jesper de Jong]

What operating system? Windows?

You could do something like this:

set TEST_PATH=D:\testing
java -Dtest.path=%TEST_PATH% -cp %TEST_PATH%\lib\test.jar

[Praveen Kumar Jayaram]

Thanks for all the responses.

Actually, in my scenario I've these (classpath, java options) in a configuration file. Sorry for the confusion.
My question was, is there a way to use the environment variable provided using '-D' option to java process in other option like '-cp' for classpath?

Sample configuration:

# A env var declared here
JAVA_OPTIONS=-Dtest.path="D:/Test"

# Above created env var is used in classpath
CLASSPATH=$test.path/lib/test.jar

Assumption is another process or executable reads the configuration and launches JVM by passing the Java options & classpath configured above.

[Jeff Verdegan]

Praveen Kumar Jayaram wrote:Thanks for all the responses.

Actually, in my scenario I've these (classpath, java options) in a configuration file. Sorry for the confusion.
My question was, is there a way to use the environment variable provided using '-D' option to java process in other option like '-cp' for classpath?

What you provide with -D are not environment variables. They're system Properties.

Sample configuration:

JAVA_OPTIONS=-Dtest.path="D:/Test"
CLASSPATH=$test.path/lib/test.jar

Assumption is another process or executable reads the configuration and launches JVM by passing the Java options & classpath configured above.

So you want to know if it's possible for some other process (A shell script? A batch file? Some other .exe? A different Java process? Perl script?) to read the above lines from a file and pass them on the command line to an invocation of the java executable?

If so, yes, it's possible.

However, I'm afraid your question is still not very clear. At least not to me.

[Praveen Kumar Jayaram]

Thanks for correcting me. You got it right!

I've a 3rd party executable which picks up the java options and classpath and launches JVM by passing those configured parameters.
So am looking for a standard approach supported by Java to use the system property defined using "-D" option, in classpath (using "-cp" option).
Is there any standard approach?

[Jeff Verdegan]

Praveen Kumar Jayaram wrote:
So am looking for a standard approach supported by Java to use the system property defined using "-D" option, in classpath (using "-cp" option).
Is there any standard approach?

Huh? I have no idea what you mean. Are you saying that if your Java app is invoked as java -Dabc=xyz -cp pqr MyApp, then you want your app to use "xyz" as its classpath? If that's what you want, it's not possible exactly as stated. You would have to either

A) Have your app use ProcessBuilder or Runtime.exec() to launch another JVM after getting the "abc" system property to pass to that command line.

or

B) Have your app create a ClassLoader that uses the value of the "abc" system property to find its classes, and use that throughout your app.

A better approach, however, would be to just have the "xyz" in the proper place in the command line to start with.

[Praveen Kumar Jayaram]

Thanks for the clarification and the alternative approaches.
As I mentioned, the JVM would be launched by a 3rd party executable and hence I can't play around with the way how the JVM is launched.

Looks this is not achievable the way I expected. Marking the thread as closed.