Question

I’m developing a Groovy shell script which is launched frequently (doing rather small tasks), therefore I need a fast JVM startup time. To achieve that I’m trying to launch it with Nailgun.

I have installed Nailgun as an Ubuntu package. Then I fixed the argument bug by linking /usr/bin/ng-server to /usr/bin/ng. I’m starting the Nailgun-Server like this:

java -cp /usr/share/java/nailgun-0.7.1.jar -server com.martiansoftware.nailgun.NGServer

I have this simple dummy Groovy script named hello.groovy just to test the nailgun-server:

#!/usr/bin/env groovy
def sayHello() {
  println("Hello Groovy!");
}

sayHello();

I compiled the file with groovyc to hello.class.

Now I want to launch that script within the Nailgun server. My naive approach to do that would be:

ng hello
ng hello.sayHello

But all I get are ClassNotFoundExceptions:

java.lang.ClassNotFoundException: hello
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:169)
    at com.martiansoftware.nailgun.NGSession.run(Unknown Source)

So, what is the right way to launch my Groovy script with the Nailgun Server? I’d also appreciate some good sites/tutorials about how to use Nailgun, it’s really hard to get any information how to use it…

EDIT:

I would also appreciate a complete example (including how a specific class is called with ng) for using nailgun with pure Java classes, as I could also not get ng working with any Java class.

Answer 1

Finally got it. I just did not understand that I have to add all needed classes to the Nailgun classpath first (this SO question gave me the final hints).

First, add Groovy to the classpath:

ng ng-cp /usr/share/java/groovy-all.jar

Then add the directory which contains the Groovy script/Java class to the classpath, in my case it’s:

ng ng-cp /home/$USER/tools/groovy

Now I can run my Groovy script with Nailgun like this:

ng hello