HtmlUnit ajax执行问题解决

1.问题

参照htmlUnit官方get started文档的Submitting a form 栏，编写一个提交表单到百度搜索的例子，执行报错，错误信息：

严重: runtimeError: message=[An invalid or illegal selector was specified (selector: 'meta:eq(0)' error: Invalid selector: meta:eq(0)).] sourceName=[http://s1.bdstatic.com/r/www/cache/static/jquery/jquery-1.10.2.min_f2fb5194.js] line=[11] lineSource=[null] lineOffset=[0]

例子代码如下：

@Test
	public void submittingForm() throws Exception {
		final WebClient webClient = new WebClient();

		// Get the first page
		final HtmlPage page1 = webClient.getPage("http://www.baidu.com/");

		// Get the form that we are dealing with and within that form,
		// find the submit button and the field that we want to change.
		final HtmlForm form = page1.getFormByName("f");

		final HtmlSubmitInput button = form.getInputByValue("百度一下");
		final HtmlTextInput textField = form.getInputByName("wd");

		// Change the value of the text field
		textField.setValueAttribute("htmlUnit");

		// Now submit the form by clicking the button and get back the second
		// page.
		final HtmlPage page2 = button.click();
		System.out.println(page2.asXml());

		webClient.closeAllWindows();
	}

2.查找原因

(1)从错误结果看，是jquery 的选择器非法或无效。

(2)选择器怎么会无法定位到元素的呢？是不是html元素没有加载到，而执行的js需要选择定位它，然后导致上述错误？

(3)在百度上真实搜索htmlUnit 与上述程序打印的html文档作比较。发现确实有不同，前者html页body中确实存在"<meta http-equiv="refresh" ..."标签，而后者没有。

(4)怎么会没有的呢？html元素除了静态请求得到外，还有一种是ajax动态请求得到，会不会ajax动态请求在我执行page2.asXml时还没执行？

(5)到htmlUnix use script栏下查看资料，发现其中一句“Usually, you should wait() or sleep() a little, as HtmlUnit can finish before the AJAX response is retrieved from the server, please read this FAQ”，原来ajax请求真会在htmlUnit finish 后执行。点击this FAQ找到解决方法

3.解决方法

（1）第一种方法貌似是让ajax的异步执行重新同步，测试下来,仍然报错。

(2) 第二种方法是让使用HtmlUnit的main线程等待指定的毫秒数，给ajax执行时间，一旦时间用完，返回还未执行的ajax数量，并继续执行main线程，测试下来可行。

(3) 第三种方法是挂起main线程直到条件满足(比如页面中某个元素存储)，或者超出一定的次数。测试下来可行。

第三种方法个人觉得比较好，所以我采用了第三种方式，代码如下：

@Test
	public void submittingForm() throws Exception {
		final WebClient webClient = new WebClient();

		// Get the first page
		final HtmlPage page1 = webClient.getPage("http://www.baidu.com/");

		// Get the form that we are dealing with and within that form,
		// find the submit button and the field that we want to change.
		final HtmlForm form = page1.getFormByName("f");

		final HtmlSubmitInput button = form.getInputByValue("百度一下");
		final HtmlTextInput textField = form.getInputByName("wd");

		// Change the value of the text field
		textField.setValueAttribute("htmlUnit");

		// Now submit the form by clicking the button and get back the second
		// page.
		final HtmlPage page2 = button.click();
		for (int i = 0; i < 20; i++) {
			if (!page2.getByXPath("//div[@class='c-gap-top c-recommend']").isEmpty()) {
				break;
			}
			synchronized (page2) {
				page2.wait(500);
			}
		}
		FileWriter writer = new FileWriter("baidu.html");
		writer.write(page2.asXml());
		writer.close();
		// System.out.println(page2.asXml());

		webClient.closeAllWindows();
	}

HtmlUnit ajax执行问题解决

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