conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(SimpleCrawler.timeout);
		      conn.setReadTimeout(SimpleCrawler.timeout);
		      conn.setRequestProperty( "Host", url.getAuthority() );
		      conn.setRequestProperty( "User-Agent", userAgent );
		      conn.setRequestProperty( "Accept", SimpleCrawler.acceptPageType);//text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
		      conn.setRequestProperty( "Accept-Language", SimpleCrawler.acceptLanguage );
		      conn.setRequestProperty( "Accept-Encoding", "gzip, deflate, br" );
InputStream input = conn.getInputStream();
			  byte[] buffer = new byte[4096];
			  int n;

			  OutputStream output = new FileOutputStream( chemin );
			  while ((n = input.read(buffer)) != -1) 
			  {
			      output.write(buffer, 0, n);
			  }
			  output.close();

 Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("127.0.0.1", 8888));
		    	  conn = (HttpURLConnection) url.openConnection(proxy);

if (oSession.fullUrl.Contains("go_proxy=1"))
{	
       oSession["ui-backcolor"] = "green";
      oSession["x-OverrideGateway"] = "socks=192.168.5.201:1080";
      FiddlerObject.log("log："+oSession["X-OverrideGateway"]);
}

Strangely, when I set the proxy outside the if statement, it works. But when I set the proxy inside the if statement, it doesn't work.

oSession["x-OverrideGateway"] = "socks=192.168.5.201:1080";
if (oSession.fullUrl.Contains("go_proxy=1"))

{	

       oSession["ui-backcolor"] = "green";

      oSession["x-OverrideGateway"] = "socks=192.168.5.201:1080";

      FiddlerObject.log("log："+oSession["X-OverrideGateway"]);

}