A question about ClassLoader

[kong song]

Hi all:

The following code is extracted from org.apache.commons.chain.CatalogFactory source code.

        ClassLoader cl = Thread.currentThread().getContextClassLoader();
        if (cl == null) {
            cl = CatalogFactory.class.getClassLoader();
        }
        return cl;

Who can tell me under what conditions, Thread.currentThread().getContextClassLoader()==null,and fall down to execute

        if (cl == null) {
            cl = CatalogFactory.class.getClassLoader();
        }

Why did it do this ?
Thanks for any comments !

Basell

[Rob Spoor]

From the Javadoc of Thread.getContextClassLoader():

Returns:
the context ClassLoader for this Thread, or null indicating the system class loader (or, failing that, the bootstrap class loader)