I know you asked for non project creating methods to accomplish this but as this specific issue has been on my mind for quite some time I figured I would throw in another alternative.
TLDR: jump to the "Creating an Executable CLI Command" section below
Background
I had pretty much the same list of requirements as you do a while back and landed on creating executable jar files. I'm not talking about executable via java -jar myfile.jar, but rather self-contained uber-jars which you can execute directly as you would with any other binary file.
If you read the zip file specification (which jar files adher to as a jar file is a zip file), it turns out this is actually possible. The short version is that you need to:
- build a fat jar with the stuff you need
- insert a bash / bat / shell script into the binary jar content at the beginning of your file
chmod +x the uber jar file (or if on windows, check the executable box)- rewrite the jar file meta data records so that the inserted script text does not invalidate the zip file internal offsets
It should be noted that this is actually supported by the zip file specification. This is how self extracting zip files etc work and the resulting fat jar (after the above process) is still a valid jar file and a valid zip archive. All relevant commands such as java -jar still work and the file is now also executable directly from the command line.
In addition, following the above pattern it is also possible to add support for things like the drip jvm launcher which greatly accelerates the startup times of your cli scripts.
As it turns out when I started looking into this about a year ago, a library for the last point of rewriting the jar file meta data did not exist. Not just in clojure but on the JVM as a whole. This still blows my mind: the central deployment unit of all languages on the jvm is the jar file and there was no library out there that actually read the internals of jar files. Internals as in the actual zip file structure, not just what java's ZipFile and friends does.
Furthermore, I could not find a library for clojure which dealt with the kind of binary structure the zip file specification required in a clean way.
Solution:
- octet has what I consider the cleanest interface of the available binary libraries for clojure, so I wrote a pull request for octet adding support for the features required by the zip file specification.
- I then created a new library clj-zip-meta which reads and interprets the zip file meta data and is capable of the offset rewriting described in the last point above.
- I then created a pull request to an existing clojure lib lein-binplus to add support for the zip meta rewriting implemented by clj-zip-meta and also add support for custom preamble scripts to be able to create real executable jars without the need for
java -jar.
- After all this I created a leiningen template cli-cmd to support creating cli command projects which support all the above bells and whistles and has a well structured command line parsing setup...or what I considered well structured : ). Comments welcomed.
Creating an Executable CLI Command
So with all that, you can create a new command line clojure app with leiningen and run it using:
~> lein new cli-cmd mycmd
~> cd mycmd
~> lein bin
Compiling mycmd.core
Compiling mycmd.core
Created /home/mbjarland/tmp/clj-cmd/mycmd/target/mycmd-0.1.0-SNAPSHOT.jar
Created /home/mbjarland/tmp/clj-cmd/mycmd/target/mycmd-0.1.0-SNAPSHOT-standalone.jar
Creating standalone executable: /home/mbjarland/tmp/clj-cmd/mycmd/target/mycmd
Re-aligning zip offsets
~> target/mycmd
---- debug output, remove for production code ----
options {:port 80, :hostname "localhost", :verbosity 0}
arguments []
errors nil
summary
-p, --port PORT 80 Port number
-H, --hostname HOST localhost Remote host
--detach Detach from controlling process
-v Verbosity level; may be specified multiple times to increase value
-h, --help
--------------------------------------------------
This is my program. There are many like it, but this one is mine.
Usage: mycmd [options] action
Options:
-p, --port PORT 80 Port number
-H, --hostname HOST localhost Remote host
--detach Detach from controlling process
-v Verbosity level; may be specified multiple times to increase value
-h, --help
Actions:
start Start a new server
stop Stop an existing server
status Print a server's status
Please refer to the manual page for more information.
Error: invalid action '' specified!
Where the output from the command is just the boilerplate sample command line parsing I've added to the leiningen template.
The custom preamble script is located at boot/jar-preamble.sh and it has support for drip. In other words, if you have drip on your path, the generated executable will use it, otherwise it will fall back to standard java -jar way of launching the uber jar internally.
The source for the command line parsing and the code for the cli app live under the src directory as per normal.
If you feel like hacking, it is possible to change the preamble script and re-run lein bin and the new preamble will be inserted into your executable by the build process.
Also it should be noted that this method still does java -jar under the covers so you do need java on your path.
Ayway, long-winded explanation, but hopefully it will be of some use for somebody with this problem.
