title: HtmlUnit behind proxy
body: <p>I'm using HtmlUnit to get some information from a website. It works when I'm not behind a proxy. When working behind a proxy, I use this code to set the configuration:</p>
  
  <pre><code>WebClient webClient = new WebClient(BrowserVersion.FIREFOX_45);
  ProxyConfig proxyConfig = new ProxyConfig();
  proxyConfig.setProxyAutoConfigUrl(proxyAutoConfigUrl);
  webClient.getOptions().setProxyConfig(proxyConfig);
  HtmlPage page = webClient.getPage(config.read().getString("homepage.url"));
  FrameWindow fw = page.getFrameByName("mainDataIframe");
  ...
  </code></pre>
  
  <p>But I always get an error: </p>
  
  <pre><code>    ERROR AWT-EventQueue-0 com.gargoylesoftware.htmlunit.html.HtmlPage - Error loading JavaScript from [some website].
  java.io.IOException: Unable to download JavaScript from 'some website' (status 404).
      at com.gargoylesoftware.htmlunit.html.HtmlPage.loadJavaScriptFromUrl(HtmlPage.java:1040)
      at com.gargoylesoftware.htmlunit.html.HtmlPage.loadExternalJavaScriptFile(HtmlPage.java:967)
      at com.gargoylesoftware.htmlunit.html.HtmlScript.executeScriptIfNeeded(HtmlScript.java:352)
      at com.gargoylesoftware.htmlunit.html.HtmlScript$2.execute(HtmlScript.java:238)
      at com.gargoylesoftware.htmlunit.html.HtmlScript.onAllChildrenAddedToPage(HtmlScript.java:257)
      at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.endElement(HTMLParser.java:772)
      at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
      at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.endElement(HTMLParser.java:729)
      at net.sourceforge.htmlunit.cyberneko.HTMLTagBalancer.callEndElement(HTMLTagBalancer.java:1209)
      at net.sourceforge.htmlunit.cyberneko.HTMLTagBalancer.endElement(HTMLTagBalancer.java:1111)
      at net.sourceforge.htmlunit.cyberneko.filters.DefaultFilter.endElement(DefaultFilter.java:207)
      at net.sourceforge.htmlunit.cyberneko.filters.NamespaceBinder.endElement(NamespaceBinder.java:337)
      at net.sourceforge.htmlunit.cyberneko.HTMLScanner$ContentScanner.scanEndElement(HTMLScanner.java:3137)
      at net.sourceforge.htmlunit.cyberneko.HTMLScanner$ContentScanner.scan(HTMLScanner.java:2100)
      at net.sourceforge.htmlunit.cyberneko.HTMLScanner.scanDocument(HTMLScanner.java:927)
      at net.sourceforge.htmlunit.cyberneko.HTMLConfiguration.parse(HTMLConfiguration.java:506)
      at net.sourceforge.htmlunit.cyberneko.HTMLConfiguration.parse(HTMLConfiguration.java:459)
      at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
      at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.parse(HTMLParser.java:979)
      at com.gargoylesoftware.htmlunit.html.HTMLParser.parse(HTMLParser.java:241)
      at com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml(HTMLParser.java:187)
      at com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage(DefaultPageCreator.java:269)
      at com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage(DefaultPageCreator.java:157)
      at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto(WebClient.java:511)
      at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:385)
      at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:303)
      at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:450)
      at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:435)
      at com.bayer.elwasweb.PageReader.messstellenDurchlaufen(PageReader.java:99)
      at com.bayer.elwasweb.PageReader.start(PageReader.java:70)
      at com.bayer.elwasweb.Gui.actionPerformed(Gui.java:211)
      at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
      at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
      at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
      at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
      at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
      at java.awt.Component.processMouseEvent(Unknown Source)
      at javax.swing.JComponent.processMouseEvent(Unknown Source)
      at java.awt.Component.processEvent(Unknown Source)
      at java.awt.Container.processEvent(Unknown Source)
      at java.awt.Component.dispatchEventImpl(Unknown Source)
      at java.awt.Container.dispatchEventImpl(Unknown Source)
      at java.awt.Component.dispatchEvent(Unknown Source)
      at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
      at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
      at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
      at java.awt.Container.dispatchEventImpl(Unknown Source)
      at java.awt.Window.dispatchEventImpl(Unknown Source)
      at java.awt.Component.dispatchEvent(Unknown Source)
      at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
      at java.awt.EventQueue.access$500(Unknown Source)
      at java.awt.EventQueue$3.run(Unknown Source)
      at java.awt.EventQueue$3.run(Unknown Source)
      at java.security.AccessController.doPrivileged(Native Method)
      at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
      at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
      at java.awt.EventQueue$4.run(Unknown Source)
      at java.awt.EventQueue$4.run(Unknown Source)
      at java.security.AccessController.doPrivileged(Native Method)
      at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
      at java.awt.EventQueue.dispatchEvent(Unknown Source)
      at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
      at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
      at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
      at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
      at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
      at java.awt.EventDispatchThread.run(Unknown Source)
  ERROR AWT-EventQueue-0 PageReader - com.gargoylesoftware.htmlunit.ElementNotFoundException: elementName=[frame or iframe] attributeName=[name] attributeValue=[mainDataIframe]
  </code></pre>
  
  <p>This error never happens without the proxy or in a browser. Is there someone with an idea, why this error happens? Or maybe someone who knows how to find the differences when working behind the proxy?</p>