Java applet running under proxy-configured environment (corporate networks)

I am having a problem with a signed Java applet which performs simple HTTPS requests to our server (using Java's URL, Connection classes). Everything looks ok for majority of the clients. However, we do have several clients under corporate network, which are behind a proxy that requires authentication (possibly windows-logon-based authentication)). And for these clients we often hear such feedback like:

The application behaves extremely slow though our network speed is 20mbps. 20mbps connection is a huge speed for our application to work perfectly. So my first question specifically the following:

1) Can it be the case that proxy analyses the content of our requests and thus impacts the performance of the app. And could it be only a Java-specific problem ?

The next part is about Java and Java applets specifically. From forums I know there is a problem with Java selecting the right proxy configured in Browser. Sometimes Java applet fails to detect the proxy configured in IE, and the only solution is to configure it also in Java's Control Panel. Having said this, the next question is:

2) Taking into account that direct connection for the corporate clients is not allowed and Java Control Panel is not properly configured, could that be the case that Java plugin selects another - wrong proxy, thru which it eventually access to the servers and thus resulting very low performance ?

I also have tried to use Apache's HttpClient (http://hc.apache.org/httpcomponents-client-ga/), to check how it performs under such environment. I have configured the client as specified in Apache tutorial to automatically get the JRE's proxy:

httpclient = new DefaultHttpClient();

    ProxySelectorRoutePlanner routePlanner = new ProxySelectorRoutePlanner(
            httpclient.getConnectionManager().getSchemeRegistry(),
            ProxySelector.getDefault());  
    httpclient.setRoutePlanner(routePlanner);

And what we 开发者_JAVA技巧faced is an authentication required error (407) when we try to execute requests via Apache's httpclient. Specifically407 proxy authentication required. the ISA server requires authorisation to fulfill the request So the last question is about this differences between Apache and Java's client.

3) How Java Applet chooses the proxy ? and How Apache Client's selection logic differs from that of Java's ?

Please share any strongly confirmed experience you might find out could be helpful for my situation.

Thanks in advance.

3) How Java Applet chooses the proxy ?
Default behaviour:
Applet checks control panel\java\ network\network proxy settings
and uses the proxy according to the configuration in there.
Setting system properties for an applet does not works.
i.e:

System.setProperty("java.net.useSystemProxies","true"); 
System.setProperty("http.proxyHost", "1.1.1.1");
System.setProperty("http.proxyPort", "8080"); 

If you want to alter the proxy selection for an applet. then you can use ProxySelector class.
also check out this question how-to-set-http-proxy-in-an-applet
you may find it useful.