HtmlUnit爬取Ajax动态生成的网页以及自动调用页面javascript函数
HtmlUnit官网的介绍：
HtmlUnit是一款基于Java的没有图形界面的浏览器程序。它模仿HTML document并且提供API让开发人员像是在一个正常的浏览器上操作一样，获取网页内容，填充表单，点击超链接等等。
它非常好的支持JavaScript并且仍在不断改进，同时能够解析非常复杂的AJAX库，通过不同的配置来模拟Chrome、Firefox和IE浏览器。
本文针对一个足彩网站抓取的例子，来熟悉HtmlUnit
WebClient wc = new WebClient(BrowserVersion.FIREFOX_38);
wc.getOptions().setJavaScriptEnabled(true); //启用JS解释器，默认为true
wc.setJavaScriptTimeout(100000);//设置JS执行的超时时间
wc.getOptions().setCssEnabled(false); //禁用css支持
wc.getOptions().setThrowExceptionOnScriptError(false); //js运行错误时，是否抛出异常
wc.getOptions().setTimeout(10000); //设置连接超时时间 ，这里是10S。如果为0，则无限期等待
wc.setAjaxController(new NicelyResynchronizingAjaxController());//设置支持AJAX
wc.setWebConnection(
new WebConnectionWrapper(wc) {
public WebResponse getResponse(WebRequest request) throws IOException {
……
}
}
);
HtmlPage page = wc.getPage("http://XXXX.com/");
FileWriter fileWriter = new FileWriter("D:\\text.html");
String str = "";
//获取页面的XML代码
str = page.asXml();
fileWriter.write( str );
//关闭webclient
wc.close();
fileWriter.close();
解决数据乱码问题
该网站数据是由js动态载入，并且js有2种编码：
<script language="javascript" src="XXX.js" charset="gb2312"></script>
<script language="javascript" src="XXX.js" charset="utf-8"></script>
可以通过重写WebConnectionWrapper类的getResponse方法来修改返回值
例如，对bfdata.js的返回结果做修改
wc.setWebConnection(
new WebConnectionWrapper(wc) {
public WebResponse getResponse(WebRequest request) throws IOException {
WebResponse response = super.getResponse(request);
if (request.getUrl().toExternalForm().contains("bfdata.js")) {
String content = response.getContentAsString("GBK");
WebResponseData data = new WebResponseData(content.getBytes("UTF-8"),
response.getStatusCode(), response.getStatusMessage(), response.getResponseHeaders());
response = new WebResponse(data, request, response.getLoadTime());
}
return response;
}
}
);
解决Content is not allowed in prolog
报错信息：
六月 21, 2016 4:15:06 下午 com.gargoylesoftware.htmlunit.xml.XmlPage <init>
警告: Failed parsing XML document http://XXX/vbsxml/goalBf3.xml?r=0071466496906000: Content is not allowed in prolog.
六月 21, 2016 4:15:06 下午 com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine handleJavaScriptException
信息: Caught script exception
======= EXCEPTION START ========
EcmaError: lineNumber=[41] column=[0] lineSource=[<no source>] name=[TypeError] sourceName=[http://XXX/common2.js] message=[TypeError: Cannot read property "childNodes" from null (http://XXX/common2.js#41)]
com.gargoylesoftware.htmlunit.ScriptException: TypeError: Cannot read property "childNodes" from null (http://XXX/common2.js#41)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine$HtmlUnitContextAction.run(JavaScriptEngine.java:865)
at net.sourceforge.htmlunit.corejs.javascript.Context.call(Context.java:628)
at net.sourceforge.htmlunit.corejs.javascript.ContextFactory.call(ContextFactory.java:513)
at com.gargoylesoftware.htmlunit.javascript.JavaScriptEngine.execute(JavaScriptEngine.java:747)
at com.gargoylesoftware.htmlunit.html.HtmlPage.loadExternalJavaScriptFile(HtmlPage.java:1032)
at com.gargoylesoftware.htmlunit.html.HtmlScript.executeScriptIfNeeded(HtmlScript.java:395)
at com.gargoylesoftware.htmlunit.html.HtmlScript$3.execute(HtmlScript.java:276)
其中警告信息：Content is not allowed in prolog是导致后面报错的原因，而Content is not allowed in prolog是因为解析内容内包含BOM。这个标记是看不到的，而在流里面有这个标记。
因此可以通过以下代码来截取你需要的内容
wc.setWebConnection(
new WebConnectionWrapper(wc) {
public WebResponse getResponse(WebRequest request) throws IOException {
WebResponse response = super.getResponse(request);
if(request.getUrl().toExternalForm().contains("goalBf3.xml")){
String content = response.getContentAsString("UTF-8");
if(null != content && !"".equals(content)){
if(content.indexOf("<") != -1 && content.lastIndexOf(">") != -1 && content.lastIndexOf(">") > content.indexOf("<"))
content = content.substring(content.indexOf("<"), content.lastIndexOf(">") + 1);
}
WebResponseData data = new WebResponseData(content.getBytes("UTF-8"),
response.getStatusCode(), response.getStatusMessage(), response.getResponseHeaders());
response = new WebResponse(data, request, response.getLoadTime());
}
return response;
}
}
);
调用页面javascript函数
该网站有些数据是通过鼠标悬停来获得数据
我们可以通过page.executeJavaScript来执行js
例如：
HtmlPage page = wc.getPage("http://xxx.com/");
wc.waitForBackgroundJavaScript(30 * 1000); /* will wait JavaScript to execute up to 30s */
ScriptResult result = page.executeJavaScript("document.getElementById('pk_1248827').onmouseover(window.event)");
HtmlPage jspage = (HtmlPage) result.getNewPage();