Re: classpath question

[Scott Klement <midrange-l@xxxxxxxxxxxxxxxx>]

Hi Tim,

First of all, you don't want /QIBM/UserData/Java400/ext in your 
CLASSPATH.  That directory is for "java extensions" that are always 
loaded in all Java invocations.  So stuff there is ALWAYS loaded, no 
matter what the application is, and is completely separate from the 
classpath.

The reason you don't want to use that directory for everything, even 
though it seems simple, is it can cause version conflicts.  Your whole 
system uses /QIBM/USerData/JAva400/ext, so if one piece of software 
needs one version of something, and another piece needs another version 
of something, you'd be in trouble if it's in "ext".  Not to mention that 
loading unnecessary code with every Java program is inefficient.

As for the CLASSPATH itself -- remember it's a list of places to look 
for Java classes.  Just as a library list is a list of places to look 
for programs (et al).  Each thing in the classpath is a "container" 
(much like a library is a container for programs).

a JAR file is a ZIP file containing many Java "CLASS" objects.  So it is 
a container -- just like a library would be.

You can also put CLASS files directly in an IFS directory and reference it.

But you can't just reference a directory that contains JAR files.. you 
have to list the files themselves, because JARs are containers.  They're 
not the CLASS files themselves.

-SK


On 2/6/2013 11:36 AM, tim.dclinc@xxxxxxxxx wrote:
> im using Scott's POI to write excel documents. I placed the jar files in
> the ifs "java" folder. I modified the classpath as follows:
>
> /QIBM/UserData/Java400/ext/:/java/poi3.1/
>
> when i try executing my code, i get a class not found error. I modified
> the classpath as follows again:
>
> /QIBM/UserData/Java400/ext/:/java/poi3.1/poi3.1.jar
>
> and now it works.
>
> Im not sure why i have to specify the jar file in the classpath. Why
> doesnt it work just specifying the folder the jars are contained in.