I am trying to build a very rudimentary crawler which could move through certain specific links and extract the contents from them. I am using JSoup for traversing through the links on a page and reading the required content.
However I have hit a roadblock on one of the sites. It is a kind of news portal on which users are allowed to post their own comments. I need to extract these comments. However if there are more than 5 comments, they are spread over several pages and the links to the subsequent pages are created by a JavaScript code in href (instead of a real link). It is something like this:
<a id="pager1_lnkPage2" href="javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("pager1$lnkPage2", "", true, "", "", false, true))">2</a>
Now I have no idea how to traverse through the links generated by this JavaScript. Is there any way to get the data on the pages referred to by these links (on the face of it this does not seem to create any new link since the URL does not change while we navigate through other pages)?
For your reference here is a link to one such page. The links to navigate through multiple pages are at the lower right corner of the page.
This is embedded on the page with the main story in an iframe.
I have also come across an interface called ScriptEngine in javax but I could not understand it well enough to use it here.
Thanks
I've never used jsoup, but judging by its description (it is HTML parser) and the fact you try to somehow incorporate javascript into it, is telling me that you chose wrong tool for the job.
In your case I would rather go with Zombie.js (Node.js based) or Selenium. Latter may be better choice if you want to stick with Java (Selenium has Java based plugins).
Related
I'm trying to use Jsoup to gather wave height information from Surfline.com. I have the element I desire in the screenshot and the it's showing in the dev tools. When I scrape the site with Jsoup, the returned string includes everything seen in the dev tool but the "1-2ft" which is what I need. The site is Javascript heavy and I'm assuming that jsoup is snagging the html before the javascript actually runs (I have no clue really). Do I need to specifically tell jsoup to wait for the pageload or am I missing some other critical component?
This is the code I'm using.
Document doc = Jsoup.connect("http://www.surfline.com/surf-report/folly-beach-pier-southside-southeast_5294/").get();
Elements content = doc.select("div[id=current-surf-range]");
System.out.println(content);
and this is the output I'm seeing in my IDE
<div id="current-surf-range" style="font-size:21px;font-weight:bold;padding-top:7px; padding-bottom: 7px;"></div>
it seems really odd that the contents of the div wouldn't be returned with it. This is my first time using Jsoup and I tried to read through the docs as best I could but nothing seemed to touch on this particular issue. Any insight would be awesome and greatly appreciated.
What you see in the browser is not what necessarily you would get when download the page by URL with your HTTP library of a choice. In fact, you should never expect them to be the same. In the modern web, webpages are quite dynamic and are loaded asynchronously involving multiple API calls to different resource providers and javascript being executed in the browser (which has the javascript engine).
What you get with JSoup in this case is the initial HTML that browser starts to form the page with. Then, there is a set of XHR calls to the surfline API that brings the data into the browser which then dynamically fills up different parts of the page, including the current surf range.
The simplest way to approach the problem is to switch to browser automation tool called selenium which would fire up a real browser. You can then wait for the current surf range element to have a value and, if you wish to continue with JSoup, get the page source and feed it to JSoup for further parsing.
Another approach would involve looking into the requests that the page makes in the browser developer tools and then try to simulate these requests in your code, parsing the JSON responses and extracting the surf forecast data.
I use Java. I want to get web page source code but on the page works JavaScript and I want get code generated by JavaScript (code which we see in firebug in firefox)
Anyone knows what I should do?
To inspect the page after modification by JavaScript, you need a client-side JavaScript engine that can run the scripts and then let you inspect the DOM.
HtmlUnit can do this - it is a "GUI-Less browser for Java programs".
See also this question
However, this won't give you the exact original page source, because that has already been parsed into a DOM by this point.
I think you want to see the source code of DOM Elements created after the page load via AJAX.
If that´s what you want, the only way to see it is through a DOM inspector, like firebug in firefox or Developers Tools in Chrome.
Going to "View source code" only shows the source at load-time.
If I understand your question, yes your javascript objects can be passed back to your java backend either by a creating a html <form> element with inputelements, fill them with your values and then submit the form, or asynchronously via ajax/json (which doesn't require re-loading your web page). For both methods you need to configure an endpoint on your java side to receive the submitted data and return some kind of confirmation to the client, i.e. your javascript. I would recommend googling "jQuery.post" for the javascript side and finding some examples for your java backend.
The data I want is visible from the browser, but I can't find it from the html source code. I suspect the data was generated by scripts. I'd like to grad such kind of data. Is it possible using Jsoup? I'm aware Jsoup just does not execute Javascript.
Take this page for example, I'd like to grab all the colleges and schools under Academics -> COLLEGES & SCHOOLS.
If the dom content is generated via scripts or plugins, then you really should consider a scriptable browser like phantomjs. Then you can just write some javascript to extract the data.
I didn't check your link, and I assume you're looking for a general answer not specific to any page.
i want to display an external webpage (exactly as it's rendered in that site) into a webpage in my application in a way that's fast and better for SEO crawlers, and i was wondering if there's a way to do that with javaee ?
if not then what is better in performance and for SEO the XMLHTTPRequest way or the iframes way.
please advise with sample code or link if possible, thanks
Update: example website is: http://www.akhbarak.net/
If you need to display content from different pages inline, use iframe (iframe stands for inline frame - it has nothing to do with Apple).
If you'd like to use AJAX to display pages, I would recommend colorbox.
Note that accessing pages in a different domain via AJAX is next to impossible - this is a very, very big security hole. I would not recommend doing it. You would have to use a proxy on your own server to fetch the page and return its HTML.
That said, using the iframe in your source code, so it is loaded with the rest of the page, seems like your best bet. Sites like facebook and twitter use this in embeddable "like" and "tweet" widgets so that those widgets can make requests on their own domain - that is, twitter or facebook. While managing lots of iframes isn't very fun, it is a very accepted way of doing what you want to do.
In theory, you could
load the whole page into a PHP variable,
replace the body tags with ,
take out the html tags,
pull out the entire section and put it in the encompassing pages ,
and replace all links with absolute ones (ie '/images' changes to 'http://example.com/images')
Would it be easy to do? Probably not. It's the only way I can think of to accomplish it so that the site appears as part of yours though.
What I am trying to do is a take a list of URL's and download each URL's content (for indexing). The biggest problem is that if I encounter a link that is something like a facebook event that simply redirects to the login page I need to be able to detect and skip that URL. It seems as though the robots.txt file is there for this purpose. I looked into heritrix, but this seems like way more than I need. Is there a simpler tool that will provide information about robots.txt and scrape site accordingly?
(Also, I don't need to follow additional links and build up a deep index, I just need to index the individual pages in the list.)
you could just take the class you are interested in ie http://crawler.archive.org/xref/org/archive/crawler/datamodel/Robotstxt.html