Re: how to execute a class as an external Java application

Lew <>
Wed, 05 Aug 2009 09:15:54 -0400
Marcin Rodzik wrote:

Thank you for your help, now it seems to me that I managed to reduce
the problem to one specific issue with JAR files.

Before I used IDE which places all the classes into a build/classes
subdirectiories (reflecting the package structure). So I added a JVM
argument "-cp build/classes", and now it works from IDE :) no matter
if I specify class to be invoked with packagename/ClassName or
packagename.ClassName (dots are traslated into slashes). The only
condition which has to be fulfilled is that there must exist directory
packageName with a file ClassName.class in the working directory or
the directory pointed with -cp switch. And is OK. It was not so
difficult to find out, but I got that only after I read John's

Now, how to do it if I pack my program into a JAR? When I launch JAR,
the package with the class I need are not in the working directory but
in the JAR... I believe Arne's code can deal with this issue, anyway I
have not yet succeeded... I'll be working further.

You specify the JARs that belong in the class path in the "Class-Path" element
of the JAR manifest. Typically that means deploying the dependency JARs in a
subdirectory (possibly ./ ) of the one that holds the application JAR.
Running a Java class with "java -jar", Java ignores the CLASSPATH environment
variable (envar) and "-classpath" command-line option, taking its class path
entirely from the JAR manifest.

Others have linked you to docs.


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