How to get classpath in Groovy?

Question

How can I get current value of CLASSPATH in Groovy?

Solution 1

This doesn't work?

System.getProperty('java.class.path')

Solution 2

Shameless stolen from http://blog.blindgaenger.net/print_groovys_classpath_for_debugging.html This code will go up the classloader tree and printout each classloader and the associated classpath.

def printClassPath(classLoader) {
  println "$classLoader"
  classLoader.getURLs().each {url->
     println "- ${url.toString()}"
  }
  if (classLoader.parent) {
     printClassPath(classLoader.parent)
  }
}
printClassPath this.class.classLoader

Solution 3

You should be able to get the classpath from the SystemClassLoader, providing it is an URLClassLoader:

URL[] classPathUrls = ClassLoader.getSystemClassLoader().getURLs();

Solution 4

java.class.path doesn't work properly, at least in Groovy 2.1.6 (Mac OS X 10.6.8).

HelloWorld.groovy:

public class HelloWorld {

    public static void main(def args) {
        System.out.println( "Hello, world!\n");
        System.out.println(System.getenv("CLASSPATH")+"\n");
        System.out.println(System.getProperty("java.class.path"));
    }
}

Then

export CLASSPATH=/etc
groovy -classpath /usr HelloWorld.groovy

Result:

Hello, World!

/etc

/Applications/groovy-2.1.6/lib/groovy-2.1.6.jar

Now, this is HelloWorld.java: (I had to change it a bit as Groovy and Java are not 100% compatible):

public class HelloWorld {
    public static void main(String args[]) {
         System.out.println( "Hello, world!\n");
         System.out.println(System.getenv("CLASSPATH")+"\n");
        System.out.println(System.getProperty("java.class.path"));
    }
}

Now:

javac HelloWorld.java
export CLASSPATH=/etc
java -classpath /usr HelloWorld

Result:

Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld
Caused by: java.lang.ClassNotFoundException: HelloWorld
etc. ...................

Then:

java -classpath /usr:. HelloWorld

Result:

Hello, world!

/etc

/usr:.

I'll update if I find out how to make it work in Groovy...

View more solutions

Comments

[yegor256]

It's empty :( Is it possible to get classpath form class loader?

[yegor256]

Unfortunately it's empty when I'm using Groovy inside gmaven plugin. Is it possible to get classpath from class loader somehow?

[Egon Willighagen]

Groovy seems to do funky stuff, and the java.class.path does not contain the classpath passed with groovy's -cp command line option.

[Sergey Orshanskiy]

Same thing: both the CLASSPATH environment variable and the -classpath in the command line have no effect on this list. At least in my case it is identical to what I see in the property java.class.path.

[Sergey Orshanskiy]

However, see groovy.codehaus.org/… about dynamically adding a path to classpath. this.class.classLoader.rootLoader.addURL( new URL("file:///d:/drivers/ojdbc14.jar") )

[kodstark]

It shows only groovy jar - why stackoverflow.com/a/27131375/1042297 is not accepted answer ?