URLs and URIs - Java Network Programming - page 157

Example 5-9. A ProxySelector that remembers what it can connect to
import java.io.* ;
import java.net.* ;
import java.util.* ;
public class LocalProxySelector extends ProxySelector {
private List < URI > failed = new ArrayList < URI >();
public List < Proxy > select ( URI uri ) {
List < Proxy > result = new ArrayList < Proxy >();
if ( failed . contains ( uri )
|| ! "http" . equalsIgnoreCase ( uri . getScheme ())) {
result . add ( Proxy . NO_PROXY );
} else {
SocketAddress proxyAddress
= new InetSocketAddress ( "proxy.example.com" , 8000 );
Proxy proxy = new Proxy ( Proxy . Type . HTTP , proxyAddress );
result . add ( proxy );
}
return result ;
}
public void connectFailed ( URI uri , SocketAddress address , IOException ex ) {
failed . add ( uri );
}
}
As I said, each virtual machine has exactly one ProxySelector . To change the Proxy
Selector , pass the new selector to the static ProxySelector.setDefault() method,
like so:
ProxySelector selector = new LocalProxySelector ():
ProxySelector . setDefault ( selector );
From this point forward, all connections opened by that virtual machine will ask the
ProxySelector for the right proxy to use. You normally shouldn't use this in code run‐
ning in a shared environment. For instance, you wouldn't change the ProxySelector
in a servlet because that would change the ProxySelector for all servlets running in the
same container.
Communicating with Server-Side Programs Through GET
The URL class makes it easy for Java applets and applications to communicate with server-
side programs such as CGIs, servlets, PHP pages, and others that use the GET method.
(Server-side programs that use the POST method require the URLConnection class and