Question

Okay. So here’s my question: I am making a data parser in Clojure. One part of my program is that it has to be able to graph the data. I figure, I’ll use jFreeChart. However, I have absolutely NO IDEA how to include stuff in JAR files. What I mean is: if I have a app.jar file in my classpath, I don’t seem to be able to do:

import app.thing.thing2

without changing the classpath to be inside the jar file.

The idea here is that I don’t think I can change my classpath since I need to set it to run Clojure (Or do I?). The global classpath is currently /usr/share/java.

And please don’t ask me to use Maven, Ant or any project-building tool unless it is the only way to do this. This is a script for personal use that doesn’t need or want a whole lot of overhead.

I wonder if I should just unpack every JAR file, so that I can reference the directory structure? Is this bad?

Let me know if you need any clarifications!

Answer 1

The content of the (Java) CLASSPATH environment variable is available to Clojure so if you add your jar to the global classpath before to run Clojure, you’ll “see” it:

export CLASSPATH=/path/to/jfreechart.jar:$CLASSPATH

But, in my opinion, this is not the “clean” way to add a jar to Clojure’s classpath (because this makes the library visible to any Java program and may not be desired). Instead, you should use the CLOJURE_EXT environment variable. This is how this variable is documented:

# CLOJURE_EXT The path to a directory containing (either directly or as
# symbolic links) jar files and/or directories whose paths
# should be in Clojure's classpath. The value of the
# CLASSPATH environment variable for Clojure will be a list
# of these paths followed by the previous value of CLASSPATH
# (if any).

On my system, it is defined as below:

export CLOJURE_EXT=~/.clojure

So, to add jfreechart.jar (or any other library) to Clojures’s classpath, copy it (or add a symlink pointing to it) in the directory defined in the CLOJURE_EXT variable.

And by the way (I’m sorry but your question is not that clear), if you want to bundle some Java classes into a jar, the command is something like that:

$ jar cf myjarfile *.class 

You’ll find documentation of jar – the Java Archive Tool – here.