I think this should be fine for 99% of situations, but I think it's
also fair to say this is an unorthodox use of java.ext.dirs. I've
never really had a firm grip on the idiomatic use of Java's extension
mechanism, but I do know that they claim it is for well-established
extension/optional packages. One example might be the bouncycastle
crypto provider. The one thing I think you do have to be careful
about is that if you put something in the extensions path, it will be
loaded by the extensions classloader, and you will force everything
running on that JVM process to use that particular version (you can
get around this, but it's not always obvious). For most applications
this shouldn't matter, but for an application that hosts other
applications (eg. an application server) this can be problematic. I
know from experience after 3 years of dealing with IBM WebSphere. You
will probably never run into any problems, but I couldn't help but
comment.
Another solution you might want to look at is Apache's Common
Launcher. It's not the most elegant solution in the world, but it
makes it easy to add an entire directory of JARs to the classpath, and
it makes it easy to have a cross-platform execution script.
On Jan 4, 12:59 pm, "Stephen C. Gilardi" <squee...@mac.com> wrote:
> The "java.ext.dirs" System property provides a very convenient way to
> set up and maintain a Classpath for Clojure REPLs. The property can be
> set from the command line used to launch Clojure (typically within a
> launcher script). Its value is a list of directories whose *contents*
> will be the Classpath roots for Clojure.
>
> In my case, I set the value of java.ext.dirs to a list of just one
> directory. That directory contains (relative) symbolic links to all
> the Jar files and directories I want Clojure to use as its Classpath.
>
> As a concrete example, here's what I have in that directory:
>
> clojure-contrib.classes -> ../../clojure-contrib/classes
> clojure-contrib.src -> ../../clojure-contrib/src
> clojure.jar -> ../../clojure/clojure.jar
> derby.jar -> ../javadb/lib/derby.jar
> etc -> ../../../clj/etc
> itext-2.0.6.jar -> ../jfreechart/lib/itext-2.0.6.jar
> jcommon-1.0.12.jar -> ../jfreechart/lib/jcommon-1.0.12.jar
> jfreechart-1.0.9.jar -> ../jfreechart/lib/jfreechart-1.0.9.jar
> jsr166y.jar -> ../jsr166y/jsr166y.jar
> local -> ../../../clj/local
> miglayout-3.6-sources.jar -> ../miglayout/miglayout-3.6-sources.jar
> miglayout-3.6-swing.jar -> ../miglayout/miglayout-3.6-swing.jar
>
> I've enclosed the bash script I'm currently using the launch Clojure.
> The one required environment variable is CLOJURE_DIRS which I set to
> the directory containing the links above. I like how simple the script
> is and how easy it is to manage which jars and directories are
> available to Clojure REPLs using this method.
>
> --Steve
>
> (note: using this with clojure.contrib.repl-ln requires revision 337
> (of today) or later)
>
> #!/bin/bash
>
> # clj: Launches a Clojure REPL with command line arguments
> #
> # Environment variables:
> #
> # Required:
> #
> # CLOJURE_DIRS A list of paths to directories containing (either
> directly
> # or via symbolic links) the jar files and directories
> that
> # Clojure will use as its Classpath. The paths are
> separated
> # by File.pathSeparatorChar (: on UNIX).
> #
> # Optional:
> #
> # CLOJURE_MAIN The Java class to launch
> # default: clojure.main
> # example: clojure.contrib.repl_ln
> #
> # CLOJURE_OPTS Java options for this REPL's JVM instance
> # default:
> # example:"-Xms32M -Xmx128M -server"
> #
> # CLOJURE_INIT Path to an init file to run, an @ prefix specifies a
> # classpath-relative path.
> # default:
> # example:"@init.clj"
>
> set -o errexit
> set -o nounset
> #set -o xtrace
>
> JAVA=java
> OPTS=${CLOJURE_OPTS:-}
> DIRS="-Djava.ext.dirs=${CLOJURE_DIRS}"
> MAIN=${CLOJURE_MAIN:-clojure.main}
> INIT=${CLOJURE_INIT:+--init ${CLOJURE_INIT}}
> REPL=--repl
>
> exec $JAVA $OPTS $DIRS $MAIN $INIT $REPL $@
>
> smime.p7s
> 3KViewDownload
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