A codewars runner for JVM based languages. The advantage of using this runner is that it handles warming up the JVM for faster execution times.

To compile, first make sure you have JDK ≥ 1.8 and leiningen installed. Then type:

lein uberjar

This will create a JAR file target/jvm-runner-*-standalone.jar relative to the directory of this README.

The runner can be run via lein or via the compiled JAR.

By design, the JVM runner accepts JSONs with the same API as the node.js runner. These are handed as strings in stdin.

JSONs should conform to the following JSON schema:

{
    "title": "CodeWars Runner Schema",
    "type": "object",
    "properties": {
        "language": {
                "description": "The language the kata was written in",
                "type": "string"
        },
        "solution": {
            "description": "The codewars kata solution code",
            "type": "string"
        },
        "fixture": {
            "description": "The test suite for the solution code",
            "type": "string"
        },
        "setup": {
            "description": "Additional setup code",
            "type": "string"
        }
    },
    "required": ["language", "solution"]
}

1. Use lein run:

lein run <<< '{"language": "clojure", "solution": "(println 42)"}'

2. Build an uberjar and run that with java:

lein do clean, uberjar
TIMEOUT=2000 java -jar target/jvm-runner-*-standalone.jar <<< \
'{"language": "clojure", "solution": "(println 42)"}'

3. Build the Docker container, and run that:

docker build -t codewars/jvm-runner .
docker run -i -a stdin -a stdout -a stderr --rm codewars/jvm-runner <<< \
'{"language": "clojure", "solution": "(println \"42\")"}'

Examples:

• No test fixture

lein run <<< '{"language": "clojure", "solution": "(println 42)"}'

• Simple test fixture

java -jar target/jvm-runner-*-standalone.jar <<< \
'{"language": "clojure", 
"solution": "(ns a) (defn b [] 1)", 
"fixture": "(ns test (:use [a] [clojure.test])) 
            (deftest b-test (is (= 1 (b))))"}'

• No test fixture

lein run <<< '{
  "language": "java", 
  "solution": "public class Solution { 
                 public static void main() {
                   System.out.println(\"42\");}}"}'

The JVM runner is programmed to exit after the code has run for a specified timeout. Timeout defaults are controlled in the :env map in project.clj. The default is set to 2000 msecs. It behaves as follows:

lein run <<< '{"language": "clojure", "solution": "(Thread/sleep 5000) (println :ok)"}'
# Exits with exit code 1 after ~2 seconds

The default can be overidden with an environement variable:

TIMEOUT=10000 lein run <<< '{"language": "clojure", "solution": "(Thread/sleep 5000) (println :ok)"}'
# Exits with exit code 0 and prints ":ok"

Note that if you are not in this directory and running the uberjar, you will have to set the TIMEOUT environment variable manually.

lein test

For clojure, popular choices of IDE include Emacs, Vi, and LightTable. All of these, when correctly configured, should auto-detect the project.clj file and intelligently pull artifacts necessary for running and testing as necessary.

It is often desirable to use an IDE like Eclipse or IntelliJ for Java development. To do this, you will want to generate a maven pom file. This is done using leiningen as follows:

lein pom

This will generate a pom.xml file suitable for use with maven and other tools that plug into maven.

Copyright © 2014 Matthew Wampler-Doty