Does Java's ProxySelector not work with automatic proxy configuration scripts?

I want my Java program to use the system's proxy configuration. Accordingly, I used the code found in many places, such as this answer, to set java.net.useSystemProxies to true and call ProxySelector.getDefault().select(...) to discover the proxy for the particular host I want to reach. This works fine when I've configured a single explicit proxy server in Internet Properties. But if I have set "Use automatic configuration script", it always returns the DIRECT "proxy".

I know that the script works, as my browser can access the hosts for which it returns a proxy server, and without the script set, it can't. I even tried simplifying the script to its barest essentials:

function FindProxyForURL(url, host)
{
    return "PROXY my.proxy.mydomain:3128";
}

and it works in my browser, but ProxySelector.getDefault().select(...) still returns only DIRECT.

Am I missing something? (This is on Java 1.6 & Windows 7, should it matter.)

No, the Java ProxySelector does not read Proxy Auto-Config (PAC) files.

However, as suggested by Brian de Alwis as an answer to my similar question, the Proxy Vole library appears to provide that support/capability.

To provide network connectivity out of the box for you Java application you can use the Proxy - Vole library. It provides some strategies for autodetecting the current proxy settings. There are many configureable strategies to choose from. At the moment Proxy - Vole supports the following proxy detection strategies.

• Read platform settings (Supports: Windows, KDE, Gnome, OSX)
• Read browser setting (Supports: Firefox 3.x, Internet Explorer; Chrome and Webkit use the platform settings)
• Read environment variables (often used variables on Linux / Unix server systems)
• Autodetection script by using WPAD/PAC (Not all variations supported)

As already suggested by Mads Hansen, Proxy-Vole does the trick!

You just need to add the jar from the download site to your classpath (dlls are included) and this code helped me to configure the proxy stettings:

ProxySearch proxySearch = new ProxySearch();
proxySearch.addStrategy(Strategy.OS_DEFAULT); 
proxySearch.addStrategy(Strategy.JAVA); 
proxySearch.addStrategy(Strategy.BROWSER); 
ProxySelector proxySelector = proxySearch.getProxySelector(); 

ProxySelector.setDefault(proxySelector); 
URI home = URI.create("http://www.google.com"); 
System.out.println("ProxySelector: " + proxySelector); 
System.out.println("URI: " + home); 
List<Proxy> proxyList = proxySelector.select(home); 
if (proxyList != null && !proxyList.isEmpty()) { 
 for (Proxy proxy : proxyList) { 
   System.out.println(proxy); 
   SocketAddress address = proxy.address(); 
   if (address instanceof InetSocketAddress) { 
     String host = ((InetSocketAddress) address).getHostName(); 
     String port = Integer.toString(((InetSocketAddress) address).getPort()); 
     System.setProperty("http.proxyHost", host); 
     System.setProperty("http.proxyPort", port); 
   } 
 } 
}

You can use Proxy Vole to solve this issue:

• Original Google Code project
• More recent GitHub project, forking original

If you know exactly which PAC-file you want to use, you can do:

UrlPacScriptSource source = new UrlPacScriptSource("http://www.example.org/proxy.pac");
PacProxySelector selector = new PacProxySelector(source);

ProxySelector.setDefault(selector);

The advantage of this is that it is not user-related. For example if running this as a Windows service, you may end up running it on the SYSTEM-user which may not have the same OS_DEFAULT proxy settings (if any) as the Administrator-user.

The approach using system/software values is:

ProxySearch proxySearch = new ProxySearch();
proxySearch.addStrategy(Strategy.OS_DEFAULT);
proxySearch.addStrategy(Strategy.BROWSER);
proxySearch.addStrategy(Strategy.JAVA);
ProxySelector proxySelector = proxySearch.getProxySelector();

ProxySelector.setDefault(proxySelector); 

This starts with OS_DEFAULT, then JAVA and lastly BROWSER as strategies for the proxy selector.

This code is based on the GitHub code, release version 1.0.3.

I could load Proxy Auto-Config (PAC) file on Java. Please see below codes and package. I hope this would what you were looking for:

import com.sun.deploy.net.proxy.*;
.
.
BrowserProxyInfo b = new BrowserProxyInfo();        
b.setType(ProxyType.AUTO);
b.setAutoConfigURL("http://yourhost/proxy.file.pac");       
DummyAutoProxyHandler handler = new DummyAutoProxyHandler();
handler.init(b);

URL url = new URL("http://host_to_query");
ProxyInfo[] ps = handler.getProxyInfo(url);     
for(ProxyInfo p : ps){
    System.out.println(p.toString());
}

You already have a [com.sun.deploy.net.proxy] package on your machine! Find [deploy.jar] ;D

Yes, from version 9 automatic proxy configurations (PAC/WPAD) will be read from the operating system.