[news.eclipse.tools] Re: Basic Java development question

[Michael Taege <m-taege@xxxxxxxxxxx>]

Hi Scott,

external libraries has to be within the classpath of the Java virtual 
maschine if you are executing your
Java application. Therefore you have to tell the VM where to find the 
external libraries with the '-cp' or  '-classpath' option of the java 
command.

Assuming that you have the external jars 'a.jar' and 'b.jar' the java 
command will look like this

java -cp "a.jar;b.jar;your.jar" com.yourapp.YourMain

It's a common practice to put external libraries in a folder with the name 
'lib' to make clear what external jars are needed by an application. Then 
you have to tell the VM the relative path to the libraries.

java -cp "./lib/a.jar;./lib/b.jar;your.jar" com.yourapp.YourMain

If you don't want to use the classpath option you can add an external jar 
to your jar. I have no idea if this is possible with Eclipse, but you can 
handle a jar file as a zip file (actually a jar-file is nothing else as a 
zip-file, rename the file extension from *.jar to *.zip and open it with 
WinZip or WinRar). But I think thats no good idea, because if the vendor of 
the external library publishes a new version or a bug-fix you can run into 
trouble (well, if the vendor changes package-, class-or method-names, you 
can run into trouble too, but that's another question).

Take care

Michael





Am Thu, 19 Jun 2003 03:03:36 -0400 hat Scott <scott@xxxxxxxxxx> 
geschrieben:

> I have a really basic Java question - I'm building an application using
> Eclipse that makes use of a couple of libraries that are located in
> external JAR files.  I've added them as external JARs to the Libraries 
> tab
> of the Java Build Path, and everything works fine in Eclipse.  My program
> compiles and access those libraries as expected.  However, when I export
> my project as a JAR file, and try to execute it outside of Eclipse, it
> gives me an error telling me that it can't find those libraries.  How
> should I proceed?  I can import the source code of those libraries into 
> my
> project, and then it works fine during export, but it bloats my code and
> is really unncessary as I won't be altering any of that code.  Is there a
> better way (i.e. A way to tell Eclipse to include those external JARs in
> my JAR during export, or something?)  I would definately appreciate any
> guidance, as you have already surmised I am a bit of a beginner at all
> this.  Thanks!
>
> Scott



--
-----------------------------------
Dipl. Ing. Michael Täge
Bauschlotterstr. 36
75177 Pforzheim
Fon: 07231 51278
Mobil: 0171 8067809
m-taege@xxxxxxxxxxx