Loading a local .kml file using google maps

I created a hello world program to load a local kml file (borrowed from google's docs):

var ctaLayer = new google.maps.KmlLayer("http://localhost:8080/kml/cta.kml");

This does not work (nothing gets loaded).

However, when I change that line to:

  var ctaLayer = new google.maps.KmlLayer("http://gmaps-samples.googlecode.com/svn/trunk/ggeoxml/cta.kml");

it loads properly. Both kml files are identical. What do I need to do to get it to load when serving it myself? (I tried both absolute and relative paths, and I know the paths I am using are correct…)

Also I added the correct mime type to my appserver's config file:

<mime-mapping>
    <extension>kml</extension>
<mime-type>application/vnd.google-earth.kml+xml</mime-type>
</mime-mapping>
<mime-mapping>
    <extension>kmz</extension>
    <mime-type>application/vnd.google-earth.kmz</mime-type>
</mime-mapping>

But it still doesn't load.

I found this in google's docs:

The Google Maps API supports the KML and GeoRSS data formats for displaying geographic information. These data formats are displayed on a map using a KmlLayer object, whose constructor takes the URL of a publicly accessible KML or GeoRSS file.

So I guess what I am trying to do is not possible without serving the kml from a publicly accessible url…unless someone can prove otherwise