UnmappedResourceHandler cannot convert URL in CSS to JSF 's valid URL - jsf

Question

Here is my setup:
Web app 's folder structure and file names are exactly the same as the UnmappedResourceHandler 's javadoc
UnmappedResourceHandler is already registered in faces-config.xml
/javax.faces.resource/* is already mapped to facesServlet in web.xml
The style.css is :
body {
background: url("image/background.png");
}
body .test{
background-image: url("#{resource['css:image/background.png']}");
}
Then I request http://localhost:8080/app/javax.faces.resource/style.css?ln=css and the respond is :
body {
background: url("image/background.png");
}
body .test{
background-image: url("/app/javax.faces.resource/image/background.png?ln=css");
}
I expect that all the relative URLs in CSS will be converted to the JSF 's valid URL like what #{resource} does such that I do not have to use #{resource} to refer to the relative URLs in CSS anymore , but the background 's relative URL of the body selector still remains unchanged .
Update to BalusC 's reply:
If resource library is used , adding ?ln=libraryname to all CSS images will work!
But if resource library is not used , <h:outputStylesheet name="css/style.css" /> generates <link rel="stylesheet" media="screen" type="text/css" href="/app/javax.faces.resource/css/style.css.xhtml">
If I understand correctly from this , using UnmappedResourceHandler and mapping
/javax.faces.resource/* to the facesServlet in web.xml should cause JSF generates the link of the style.css without xhtml extension.

Answer 1

You're using css as a resource library as in:
<h:outputStylesheet library="css" name="style.css" />
This is not right. It's just a folder:
<h:outputStylesheet name="css/style.css" />
This will produce /javax.faces.resource/css/style.css URL instead of /javax.faces.resource/style.css?ln=css. You've otherwise to specify it in the image URL as well:
background: url("image/background.png?ln=css");
I will update the javadoc to clarify that more.
See also:
What is the JSF resource library for and how should it be used?