No main namepsace error while running a web app in Clojure using Noir

Question

I'm using Noir.

This is my project.clj

(defproject noir "1.0.0-SNAPSHOT"
  :description "FIXME: write description"
  :dependencies [[org.clojure/clojure "1.3.0"]])

lein run gives me this error:

No :main namespace specified in project.clj.

Where am I going wrong?

Now, if I add :main my-website.server to project.clj, I get this error:

Exception in thread "main" java.lang.RuntimeException: java.lang.ClassNotFoundException: my-website.server

at clojure.lang.Util.runtimeException(Util.java:165)
    at clojure.lang.RT.classForName(RT.java:2017)
    at clojure.lang.Reflector.invokeStaticMethod(Reflector.java:206)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at clojure.lang.Reflector.invokeMatchingMethod(Reflector.java:92)
    at clojure.lang.Reflector.invokeStaticMethod(Reflector.java:225)
    at user$eval29.invoke(NO_SOURCE_FILE:1)
    at clojure.lang.Compiler.eval(Compiler.java:6465)
    at clojure.lang.Compiler.eval(Compiler.java:6455)
    at clojure.lang.Compiler.eval(Compiler.java:6431)
    at clojure.core$eval.invoke(core.clj:2795)
    at clojure.main$eval_opt.invoke(main.clj:296)
    at clojure.main$initialize.invoke(main.clj:315)
    at clojure.main$null_opt.invoke(main.clj:348)
    at clojure.main$main.doInvoke(main.clj:426)
    at clojure.lang.RestFn.invoke(RestFn.java:421)
    at clojure.lang.Var.invoke(Var.java:405)
    at clojure.lang.AFn.applyToHelper(AFn.java:163)
    at clojure.lang.Var.applyTo(Var.java:518)
    at clojure.main.main(main.java:37)
Caused by: java.lang.ClassNotFoundException: my-website.server
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at clojure.lang.DynamicClassLoader.findClass(DynamicClassLoader.java:61)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at clojure.lang.RT.classForName(RT.java:2013)
    ... 21 more

Trona

It looks like you don't have a -main function in my-website.server. How did you create the project? If you do lein noir new my-website it sets up project.clj and creates a default -main function in server.clj – Sinter

That's what I did. lein noir new appname – Trona

Answer 1

The problem is that lein don't know where to locate your -main function:

First, you shall create .clj file to run. You can specify it's namespace using ns macro. Then you shall define -main function in this namespace:

(ns my-website.server
  (:require [noir.server :as server]
            [noir.core :refer [defpage]]))

(defpage "/welcome" []
  "Welcome to Noir!")

(defn -main
  [& args]
  (server/start 4000))

Then you shall configure your project.clj:

(defproject my-website "0.1.0-SNAPSHOT"
            :description "..."
            :dependencies [[org.clojure/clojure "1.4.0"]
                           [noir "1.2.2"]]
            :main my-website.server)

[noir "1.2.2"] is the latest stable version of noir. It's best to use this one.

Do not forget to place this file into your source directory. Bu default its ./src dir in your project root. So, if your namespace is called my-website.server then lein will look for it in ./src/my-website/server.clj file (or in ./src/my_website/server.clj, I'm not sure).

Now lein run will cause lein to enter namespace my-website.server and then to run (-main) function.

See sample lein project for more info.

You can also generate project.clj for your noir project using lein noir template.

Volding

This .clj file should be called what? (Sorry, just starting up and there is a bit of a caveat of documentation to smoothen this out.) – Trona

Did that. Current error: Exception in thread "main" java.lang.RuntimeException: Unable to resolve symbol: defpartial in this context, compiling:(noir/content/defaults.clj:8) – Trona

It's some error in server.clj. lein found it, but failed to compile. – Volding

I fixed my example a little bit, try it now. Unfortunately, I cant test it myself right now. – Volding

If it won't help, try to change noir version to [noir "1.2.2"]. 1.2.2 is stable. – Volding

I think you should put it in a separate answer and I will accept it as an answer to help others. – Trona

I've got to go. I'll put it in a separate answer later if you insist, but for me it looks better to gather all useful information in one place. – Volding