leiningen with multiple main classes - clojure

Question

I'd like to have two main classes (or more) with leiningen, and then be able to choose which one at the java command line. For example I have:
(ns abc (:gen-class))
(defn -main [] (println "abc"))
(ns def (:gen-class))
(defn -main [] (println "def"))
With a project.clj having:
(defproject my-jar "0.0.1"
:description "test"
:dependencies [
]
:main abc)
Then I build with lein uberjar, and run:
java -cp my-jar-0.0.1-standalone.jar abc
java -cp my-jar-0.0.1-standalone.jar def
I get it that when I specified :main abc in the project.clj it was calling that out as the main-class in the manifest, but I couldn't get it to run without putting something. But either way when I try to run the 'def' main, I get a class not found:
Exception in thread "main" java.lang.NoClassDefFoundError: def

Answer 1

This works at least with leiningen 2.0+
(defproject my-jar "0.0.1"
:description "test"
:dependencies [
]
:profiles {:main-a {:main abc}
{:main-b {:main def}}
:aliases {"main-a" ["with-profile" "main-a" "run"]
"main-b" ["with-profile" "main-b" "run"]})
Then you can run each main like so:
lein main-a
lein main-b
Which expands to this:
lein with-profile main-a run
lein with-profile main-b run
I'm using this in one of my projects and it works perfectly.

Answer 2

I added :aot [abc def] to the project.clj to generate compiled code and it worked.

Answer 3

What worked for me in both lein 2.7.0's run task as well as from the resulting uberjar is as follows...
project.clj:
(defproject many-mains "0.1.0-SNAPSHOT"
:description "Project containing multiple main methods"
:dependencies [[org.clojure/clojure "1.8.0"]]
:main nil
:target-path "target/%s"
:profiles {:main-abc {:main many-mains.abc}
:main-def {:main many-mains.def}
:main-ghi {:main org.rekdev.mm.ghi}
:core {:main many-mains.core}
:uberjar {:aot :all}})
For source like...
$ cat src/many_mains/abc.clj
(ns many-mains.abc
(:gen-class))
(defn -main
""
[& args]
(println "Hello, from many-mains.abc!"))
This lets lein run work like...
$ lein with-profile main-abc run
Hello, from many-mains.abc!
From the command line the '-' in many-mains needs to become a '_' which makes it a legal Java classname.
$ java -cp target/uberjar/many-mains-0.1.0-SNAPSHOT-standalone.jar many_mains.abc
Hello, from many-mains.abc!
There seems to have been some behavior changes between Lein 2.7.0 and prior around the effect of :main nil on the MANIFEST.MF. What I've got here works like a champ in Lein 2.7.0. The full source is at https://github.com/robertkuhar/many-mains