FULL PRODUCT VERSION :
java version "1.6.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-beta-b59g)
Java HotSpot(TM) Client VM (build 1.6.0-beta-b59g, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
Java Web Start seems to ignore the hosts file when resolving DNS requests during jnlp loading. This leads to Web Start trying to access the wrong server, or fail to find the host, reporting an UnknownHostException during application launch.

I'm reporting the situation that is quickest to reproduce: making an application work when it shouldn't. The 'Unknown Host' exception can easily be reproduced by creating a jnlp file that points to an address that DNS won't resolve, and then create an entry in the hosts file that resolves the address to a valid server.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :

Find any given WebStart application, open the jnlp file, and write down the server that is hosting the application.

 modify your hosts file (C:\WINDOWS\system32\drivers\etc\hosts on most windows boxes), and override the host's ip address, making the hostname point to any wrong IP (127.0.0.1 in my test)

Try to launch the application.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The application should NOT launch, since the DNS lookup should resolve to the wrong address. This is the result that you'd get when using 1.5:

Exception:

JNLPException[category: Download Error : Exception: java.net.ConnectException: Connection refused: connect : LaunchDesc: null ]
at com.sun.javaws.cache.DownloadProtocol.doDownload(Unknown Source)
at com.sun.javaws.cache.DownloadProtocol.isLaunchFileUpdateAvailable(Unknown Source)
at com.sun.javaws.LaunchDownload.getUpdatedLaunchDesc(Unknown Source)
at com.sun.javaws.Launcher.downloadResources(Unknown Source)
at com.sun.javaws.Launcher.handleApplicationDesc(Unknown Source)
at com.sun.javaws.Launcher.handleLaunchFile(Unknown Source)
at com.sun.javaws.Launcher.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Wrapped Exception:

java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.<init>(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
at com.sun.javaws.net.BasicNetworkLayer.doRequest(Unknown Source)
at com.sun.javaws.net.BasicNetworkLayer.doHeadRequest(Unknown Source)
at com.sun.javaws.cache.DownloadProtocol.doDownload(Unknown Source)
at com.sun.javaws.cache.DownloadProtocol.isLaunchFileUpdateAvailable(Unknown Source)
at com.sun.javaws.LaunchDownload.getUpdatedLaunchDesc(Unknown Source)
at com.sun.javaws.Launcher.downloadResources(Unknown Source)
at com.sun.javaws.Launcher.handleApplicationDesc(Unknown Source)
at com.sun.javaws.Launcher.handleLaunchFile(Unknown Source)
at com.sun.javaws.Launcher.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Java Web Start 1.5.0_04
Using JRE version 1.5.0_04 Java HotSpot(TM) Client VM
User home directory = C:\Documents and Settings\jxm
----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
m: print memory usage
o: trigger logging
p: reload proxy configuration
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
0-5: set trace level to <n>
----------------------------------------------------
#### Java Web Start Error:
#### Unable to load resource: http://camelot-dev.kwcorp.com/camelot.jnlp

ACTUAL -
The application loads just fine, ignoring the entry in the hosts file that should point it to an invalid server.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Any JNLP file should do.
---------- END SOURCE ----------