HtmlUnit异常

Question

我很难理解这个HTMLUnit异常的含义。当我在网页上的链接上调用click（）时，就会发生这种情况。

Exception class=[net.sourceforge.htmlunit.corejs.javascript.WrappedException]
com.gargoylesoftware.htmlunit.ScriptException: Wrapped com.gargoylesoftware.htmlunit.ScriptException: TypeError: Cannot read property "offsetWidth" from null (http://webapps6.doc.state.nc.us/opi/scripts/DHTMLmessages.js#95) (javascript url#297)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine$HtmlUnitContextAction.run(JavaScriptEngine.java:534)
at net.sourceforge.htmlunit.corejs.javascript.Context.call(Context.java:537)
at net.sourceforge.htmlunit.corejs.javascript.ContextFactory.call(ContextFactory.java:538)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.execute(JavaScriptEngine.java:432)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.execute(JavaScriptEngine.java:407)
at com.gargoylesoftware.htmlunit.html.HtmlPage.executeJavaScriptIfPossible(HtmlPage.java:965)
at com.gargoylesoftware.htmlunit.html.HtmlAnchor.doClickAction(HtmlAnchor.java:87)
at com.gargoylesoftware.htmlunit.html.HtmlAnchor.doClickAction(HtmlAnchor.java:121)
at com.gargoylesoftware.htmlunit.html.HtmlElement.click(HtmlElement.java:1329)
at com.gargoylesoftware.htmlunit.html.HtmlElement.click(HtmlElement.java:1288)
at com.gargoylesoftware.htmlunit.html.HtmlElement.click(HtmlElement.java:1257)
at testapp.TestApp.main(TestApp.java:61)
Caused by: net.sourceforge.htmlunit.corejs.javascript.WrappedException: Wrapped com.gargoylesoftware.htmlunit.ScriptException: TypeError: Cannot read property "offsetWidth" from null (http://webapps6.doc.state.nc.us.js#95) (javascript url#297)
at net.sourceforge.htmlunit.corejs.javascript.Context.throwAsScriptRuntimeEx(Context.java:1802)
at net.sourceforge.htmlunit.corejs.javascript.MemberBox.invoke(MemberBox.java:196)
at net.sourceforge.htmlunit.corejs.javascript.FunctionObject.call(FunctionObject.java:479)
at net.sourceforge.htmlunit.corejs.javascript.Interpreter.interpretLoop(Interpreter.java:1701)
at net.sourceforge.htmlunit.corejs.javascript.Interpreter.interpret(Interpreter.java:854)
at net.sourceforge.htmlunit.corejs.javascript.InterpretedFunction.call(InterpretedFunction.java:164)
at net.sourceforge.htmlunit.corejs.javascript.ContextFactory.doTopCall(ContextFactory.java:429)
at com.gargoylesoftware.htmlunit.javascript.HtmlUnitContextFactory.doTopCall(HtmlUnitContextFactory.java:267)
at net.sourceforge.htmlunit.corejs.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3183)
at net.sourceforge.htmlunit.corejs.javascript.InterpretedFunction.exec(InterpretedFunction.java:175)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine$5.doRun(JavaScriptEngine.java:423)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine$HtmlUnitContextAction.run(JavaScriptEngine.java:528)
... 11 more

Answer 1

Htmlunit通常不能很好地处理js代码。如果你想点击一个链接，最好使用HTMLUnitAPI来查找元素，例如。

    page.getHtmlElementById("some_div_id");
    page.getByXPath("//div");

Answer 2

JS再次出现HtmlUnit问题。您需要更正JS代码，因为它很可能包含错误。如果您没有JS代码，那么HtmlUnit将无法解决此问题。看看我在这里提供的答案。

Answer 3

当您单击并此链接调用另一个页面时，htmlUnit在导航期间可能会对异常非常冗长。如果您单击浏览器并打开控制台，可能会看到这些错误、缺少链接或图像、调用脚本时的错误...

这些都是HtmlUnit不必要的Javascript问题。

就像我在这里说的HtmlUnit不创建HtmlPage对象，您可以设置或修改htmlUnit以防止不必要的日志。您还可以设置log4j并禁用一些异常。

因此，我们使用这些选项来保持html导航，而不会在我们使用的第一个错误/问题上停止：

webClient.getOptions().setThrowExceptionOnScriptError(false);
webClient.getOptions().setThrowExceptionOnFailingStatusCode(false);

您还可以实现空类来阻止htmlUnity在控制台上详细描述css/javaScript错误，包括：

webClient.setCssErrorHandler(new SilentCssErrorHandler());    
webClient.setJavaScriptErrorListener(new JavaScriptErrorListener(){});

小样本测试用例：

@Test
public void TestCall() throws FailingHttpStatusCodeException, MalformedURLException, IOException {      
    WebClient webClient = new WebClient(BrowserVersion.CHROME);
    webClient.getOptions().setUseInsecureSSL(true); //ignore ssl certificate
    webClient.getOptions().setThrowExceptionOnScriptError(false);
    webClient.getOptions().setThrowExceptionOnFailingStatusCode(false);
    String url = "https://www.wearvr.com/#game_id=game_4";
    HtmlPage myPage = webClient.getPage(url);
    webClient.waitForBackgroundJavaScriptStartingBefore(200);
    webClient.waitForBackgroundJavaScript(20000);
    //do stuff on page ex: myPage.getElementById("main")
    //myPage.asXml() <- tags and elements
    System.out.println(myPage.asText());

} 

此外，您可以在此处看到更多关闭HtmlUnit警告的信息