Re: Not too clear on the libraries available at run time

Owen Jacobson <>
Sun, 02 Dec 2007 23:20:04 GMT
On 2007-12-02 15:15:05 -0800, Ramon F Herrera <> said:

On Dec 2, 2:58 pm, Arne VajhHj <> wrote:

Ramon F Herrera wrote:

One of the fundamental problems with Java is that you double click on
an executable jar... and nothing happens. Or perhaps the program does
start but then it stops working, when you click on a button or menu.

Compare with an *.exe file. You double click on it, and it works.

My Java programs work beautifully when I start them from inside
JBuilder, NetBeans or Eclipse.

When I was a newbie, I made a decision: "let's just put every single
needed library in the jar file". After all, my programs were simple
and small at the time.

In Unix, you just place any ancillary stuff (*.so or *.a) under /usr/
local and a lot of programs work properly. With Java (on Windows, BTW)
where the hell am I supposed to place the third party jar libraries?

My current application is based on OpenOffice. There are 4
indispensable files:

- juh.jar
- jurt.jar
- ridl.jar
- unoil.jar

Eclipse doesn't seem to like my idea of stuffing those in the final
executable jar. So, let's try placing them in the directory:

C:\Program Files\Java\jre1.6.0_03\lib\ext

Because I have a vague recollection (no book, no tutorial mentions
this) that such place is special.

I double click and... it doesn't work.

I would like to send my application as an attachment to some friends.
All I can guarantee is that they have Java in their Windows PCs. They
will not mess around with their PATH.

This simple fact that I am describing here must have turned a whole
lot of people away from Java...

You put a Class-Path directive in the manifest of your jar file
that points to the other jar files.

It is documented.

If you want to add them system wide, then lib/ext is the place, but
not many Java apps want to use that method. Poor isolation between
apps's different versions of the same libs.


This is what I did, Arne:

Eclipse generated an executable jar for me. I changed the extension
*.jar to *.zip, then decompressed it and added this line to the

Class-Path: lib/juh.jar lib/jurt.jar lib/ridl.jar lib/unoil.jar

I zipped the folder, and renamed it back to *.jar.

When I double click, it says that the jar file is defective.


Most zip tools are incapable of generating a valid JAR file[0]. Use
the command-line 'jar' tool instead:

To expand a JAR file:
  jar xf foo.jar

To compress a directory tree into a JAR file:
  jar cmf foo.jar MANIFEST-FILENAME path/to/root
or without a manifest:
  jar cf foo.jar path/to/root


[0] The JAR file spec imposes a few brain-damaged restrictions on the
file's physical layout, which ZIP tools are unaware of. While every
JAR is a valid ZIP, not every ZIP is a valid JAR.

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