Setting proxy in java, URL vs System.setProperty ?

Question

I made an java app that gets a response time from the internet. I'm working from behind a proxy, now I have this problem that I can't figure out, here's a snipped of my code

URL website = new URL("http", proxy, Integer.parseInt(proxyPort), websiteUrl)
BufferedReader in = new BufferedReader(new InputStreamReader(website.openStream()));
long start = System.currentTimeMillis();
while ((in.readLine()) != null){}
long elapsedTimeMillis = System.currentTimeMillis()-start;

Vs

URL website = new URL(websiteUrl);
System.setProperty("http.proxyHost", proxy);
System.setProperty("http.proxyPort", proxyPort);
BufferedReader in = new BufferedReader(new InputStreamReader(website.openStream()));
long start = System.currentTimeMillis();
while ((in.readLine()) != null){}
long elapsedTimeMillis = System.currentTimeMillis()-start;

When I use

URL website = new URL(websiteUrl);
System.setProperty("http.proxyHost", proxy);
System.setProperty("http.proxyPort", proxyPort);

I get a response time of 0.064 on average

and when I use

URL website = new URL("http", proxy, Integer.parseInt(proxyPort), websiteUrl)

I get a much higher response time of 0.219. How can I tell which one is giving me an accurate timing?

Answer 1

That first version actually using a proxy. It is making an HTTP request to the proxy server. I'd recommend running your tests again but look at the HTTP response code and inspect the actual output from the URL's InputStream to see what response you are getting.

Answer 2

Check the Javadoc form the contructor you're using to instantiate your URL in the first case, it's not doing what you want:

URL(String protocol, String host, int port, String file)
Creates a URL object from the specified protocol, host, port number, and file.

In the second case you call your website thru your proxy, in the first you're calling your proxy as a web server, with something like

http://proxyhost:3128/http://mysite.com/index.html

... the response is not what you expect, and you stay in your LAN, thus the times very different.