问题
I want to use HtmlUnit (v2.21) to get some search result pages from google. This requires me to click on "people also looked for" link when searching for a person (right side, see example link), which triggers some JavaScript and changes the content of the current page. But this gives me an JavaScript Wrapper Exception (see below).
Clickable example link: https://www.google.de/search?ie=UTF-8&safe=off&q=nicki+minaj
Simple TestCase with errors:
String url = "https://www.google.de/search?ie=UTF-8&safe=off&q=nicki+minaj";
WebClient client = new WebClient(BrowserVersion.BEST_SUPPORTED);
HtmlPage page = client.getPage(url);
HtmlElement link = page.getFirstByXPath("//a[@class='_Zjg']");
HtmlPage newPage = link.click(); //throws exception
this.storeResultFile(newPage.asXml(), "test");
client.close();
Result:
net.sourceforge.htmlunit.corejs.javascript.WrappedException: Wrapped java.lang.NullPointerException
at net.sourceforge.htmlunit.corejs.javascript.Context.throwAsScriptRuntimeEx(Context.java:2053)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.doProcessPostponedActions(JavaScriptEngine.java:947)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.processPostponedActions(JavaScriptEngine.java:1012)
at com.gargoylesoftware.htmlunit.html.DomElement.click(DomElement.java:799)
at com.gargoylesoftware.htmlunit.html.DomElement.click(DomElement.java:742)
at com.gargoylesoftware.htmlunit.html.DomElement.click(DomElement.java:689)
I stored the xml of the "page" object and made sure that the XPath expression is valid and has results.
Anybody got any ideas?
回答1:
Looks like the JavaScript-Engine (based on Rhino) is very easy to upset and quits on some script-issues, where other browsers are still able to run the script. I dont know if there is a mistake in the scripts from google, but these two lines solved it for me:
JavaScriptEngine engine = client.getJavaScriptEngine();
engine.holdPosponedActions();
Nevertheless, when running multiple htmlunit-objects in multiple threads it is still possible to get accross this error. This is more a workaround than a solution.
来源：https://stackoverflow.com/questions/37024296/javascript-exception-in-htmlunit-when-clicking-at-google-result-page