Find where java class is loaded from

java classpath classloader
luke picture luke · Oct 22, 2008 · Viewed 179.5k times · Source

Does anyone know how to programmaticly find out where the java classloader actually loads the class from?

I often work on large projects where the classpath gets very long and manual searching is not really an option. I recently had a problem where the classloader was loading an incorrect version of a class because it was on the classpath in two different places.

So how can I get the classloader to tell me where on disk the actual class file is coming from?

Edit: What about if the classloader actually fails to load the class due to a version mismatch (or something else), is there anyway we could find out what file its trying to read before it reads it?

Answer

Jon Skeet picture Jon Skeet · Oct 22, 2008

Here's an example:

package foo;

public class Test
{
    public static void main(String[] args)
    {
        ClassLoader loader = Test.class.getClassLoader();
        System.out.println(loader.getResource("foo/Test.class"));
    }
}

This printed out:

file:/C:/Users/Jon/Test/foo/Test.class

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