What is the difference between Class.getResource() and ClassLoader.getResource()?

Question

Class.getResource can take a "relative" resource name, which is treated relative to the class's package. Alternatively you can specify an "absolute" resource name by using a leading slash. Classloader resource paths are always deemed to be absolute.

So the following are basically equivalent:

foo.bar.Baz.class.getResource("xyz.txt");
foo.bar.Baz.class.getClassLoader().getResource("foo/bar/xyz.txt");

And so are these (but they're different from the above):

foo.bar.Baz.class.getResource("/data/xyz.txt");
foo.bar.Baz.class.getClassLoader().getResource("data/xyz.txt");

The first call searches relative to the .class file while the latter searches relative to the classpath root.

To debug issues like that, I print the URL:

System.out.println( getClass().getResource(getClass().getSimpleName() + ".class") );

Had to look it up in the specs:

• Class.getResource(String resource)

• ClassLoader.getResource(String resource)

Class's getResource() - documentation states the difference:

This method delegates the call to its class loader, after making these changes to the resource name: if the resource name starts with "/", it is unchanged; otherwise, the package name is prepended to the resource name after converting "." to "/". If this object was loaded by the bootstrap loader, the call is delegated to ClassLoader.getSystemResource.

All these answers around here, as well as the answers in this question, suggest that loading absolute URLs, like "/foo/bar.properties" treated the same by class.getResourceAsStream(String) and class.getClassLoader().getResourceAsStream(String). This is NOT the case, at least not in my Tomcat configuration/version (currently 7.0.40).

MyClass.class.getResourceAsStream("/foo/bar.properties"); // works!  
MyClass.class.getClassLoader().getResourceAsStream("/foo/bar.properties"); // does NOT work!

Sorry, I have absolutely no satisfying explanation, but I guess that tomcat does dirty tricks and his black magic with the classloaders and cause the difference. I always used class.getResourceAsStream(String) in the past and haven't had any problems.

PS: I also posted this over here