Cannot invoke Custom Applet by jnlp in OAF page

I have a custom OAF page which embedded following:

<applet width="30" height="30" code="GetKeysApplet2" jnlp_href="http://hostname:8005/OA_HTML/GetKeysApplet2.jnlp"><PARAM NAME="_cx" VALUE="794"><PARAM NAME="_cy" VALUE="794"></applet>

When the page is loaded, I got following error:

Ignored exception: ExitException[ 3]java.io.FileNotFoundException: JNLP file error: http://hostname:8005/OA_HTML/GetKeysApplet2.jnlp. Please make sure the file exists and check if "codebase" and "href" in the JNLP file are correct.

I have put the jnlp file and corresponding jar file under $OA_HTML. The content of jnlp like below:

<?xml version="1.0" encoding="UTF-8"?>

<!-- href attribute contains relative path;