如何找到系统的代理设置？

解决方法

下面的例子展示了如何使用HttpURLConnection类的systemSetting＆GetResponse方法查找代理服务器设置和创建，把系统上的代理连接。

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Properties;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.ProxySelector;
import java.net.URI;

public class Main{
   public static void main(String s[]) 
   throws Exception{
      try {
         Properties systemSettings = 
         System.getProperties();
         systemSettings.put("proxySet", "true");
         systemSettings.put("http.proxyHost", 
         "proxy.mycompany1.local");
         systemSettings.put("http.proxyPort", "80");
         URL u = new URL("http://www.google.com");
         HttpURLConnection con = (HttpURLConnection)
         u.openConnection();
         System.out.println(con.getResponseCode() + 
         " : " + con.getResponseMessage());
         System.out.println(con.getResponseCode() == 
         HttpURLConnection.HTTP_OK);
      }
      catch (Exception e) {
         e.printStackTrace();
         System.out.println(false);
      }
      System.setProperty("java.net.useSystemProxies", 
      "true");
      Proxy proxy = (Proxy) ProxySelector.getDefault().
      select(new URI("http://www.yahoo.com/")).iterator().
      next();;
      System.out.println("proxy hostname : " + proxy.type());
      InetSocketAddress addr = (InetSocketAddress)
      proxy.address();
      if (addr == null) {
         System.out.println("No Proxy");
      }
      else {
         System.out.println("proxy hostname : " 
         + addr.getHostName());
         System.out.println("proxy port : "
         + addr.getPort());
      }
   }
}

结果

上面的代码示例将产生以下结果。

200 : OK
true
proxy hostname : HTTP
proxy hostname : proxy.mycompany1.local
proxy port : 80