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Parse a page (partly generated by JavaScript) by using Selenium

I've got a problem: I want to parse a page (e.g. this one) to collect information about the offered apps and save these information into a database.
Moreover I am using crawler4j for visiting every (available) page. But the problem - as I can see - is, that crawler4j needs links to follow in the source code.
But in this case the hrefs are generated by some JavaScript code so that crawler4j does not get new links to visit / pages to crawl.
So my idea was to use Selenium so that I can inspect several Elements like in a real Browser like Chrome or Firefox (I'm quite new with this).
But, to be honest, I don't know how to get the "generated" HTML instead of the source code.
Can anybody help me?

To inspect elements, you do not need the Selenium IDE, just use Firefox with the Firebug extension. Also, with the developer tools add on you can view a page's source and also the generated source (this is mainly for PHP).
Crawler4J can not handle javascript like this. It is better left for another more advanced crawling library. See this response here:
Web Crawling (Ajax/JavaScript enabled pages) using java

Download HTML of a webpage that is changed by JavaScript

The program I am writing is in Java.
I am writing a little program that will download the html of webpages and save them. It works easily for basic pages that don't use JavaScript. But how can I download the page if I want it after a script has updated it? The page I am dealing with is actually updated by Ajax which might be one step harder.
I understand that this is probably a difficult problem that involves setting up a JavaScript run time environment of some kind. I am prepared for a solution of any level of difficulty, I just don't know exactly how to approach it or where to get started.

You can't do that alone with Java only. As the page that you want to download is rendered with javascript, then you must be able to execute the javascript to get the whole rendered page.
Because of this situation, you need to use a headless browser which is a web browser that can access to web pages but can’t show the output within a GUI, aims to provide the content of web pages as fully rendered to serve to the programs or scripts.
You can start with the most famous ones which are Selenium, HtmlUnit and PhantomJS

Retrieving contents of URL after they have been changed by javascript

I am facing a problem retrieving the contents of an HTML page using java. I have described the problem below.
I am loading a URL in java which returns an HTML page.
This page uses javascript. So when I load the URL in the browser, a javascript function call occurs AFTER the page has been loaded (onBodyLoad of HTML page) and it modifies some content (one of the div id's innerHtml) on the webpage. This change is obviously visible to me in the browser.
Now, when I try to do the same thing using java, I only get the HTML content of the page , BEFORE the javascript call has occurred.
What I want to do is, fetch the contents of the html page after the javascript function call has occurred and all this has to be done using java.
How can I do this? What should my approach be?

You need to use a server side browser library that will also execute the JavaScript, so you can get the JavaScript updated DOM contents. The default browser mechanism doesn't do this, which is why you don't get the expected result.
You should try Cobra: Java HTML Parser, which will execute your JavaScript. See here for the download and for the documentation on how to use it.
Cobra:
It is Javascript-aware. DOM modifications that occur during parsing will be reflected in the resulting DOM. However, Javascript can be disabled.

For anyone reading this answer, Scott's answer above was a starting point for me. The Cobra project is long dead and cannot handle pages which use complex JavaScript.
However there is something called HTML Unit which does just exactly what I want.
Here is a small description:
HtmlUnit is a "GUI-Less browser for Java programs". It models HTML documents and provides an API that allows you to invoke pages, fill out forms, click links, etc... just like you do in your "normal" browser.
It has fairly good JavaScript support (which is constantly improving) and is able to work even with quite complex AJAX libraries, simulating either Firefox or Internet Explorer depending on the configuration you want to use.
It is typically used for testing purposes or to retrieve information from web sites.

Getting Jsoup to support dynamically generated html by JavaScript

right now I'm working on a webcrawler. This one should parse some specific sites and give me an output into an xml-file. Up to this point, it's no problem. The Crawler works and you can customize it realy quickly via a cfg-file. I use Jsoup to parse the HTML-content.
I just added a few more sites and noticed that I got a huge problem with HTML-content that is created via JavaScript. Isn't there a way to make Jsoup supporting Javascript? Or at least get the full HTML-content I can see in my browser.
I already tried HtmlUnit, but this one didn't do well. It did not give me the content I would get in my browser.
Sincerly,
Ogofo

Jsoup does not support javascript and it does not emulate a browser. Just forget about it if you're planning to execute Javascript. In my experience HtmlUnit, which is a headless browser, has given me the best results (always talking about Java frameworks).
One thing that worths trying in HtmlUnit is changing the BrowserVersion (Chrome / InternetEplorer / FireFox) while creating the WebClient instance. Some sites react in a different way and sometimes just changing that value might give you the results you expect to get.

autogenerate HTTP screen scraping Java code

I need to screen scrape some data from a website, because it isn't available via their web service. When I've needed to do this previously, I've written the Java code myself using Apache's HTTP client library to make the relevant HTTP calls to download the data. I figured out the relevant calls I needed to make by clicking through the relevant screens in a browser while using the Charles web proxy to log the corresponding HTTP calls.
As you can imagine this is a fairly tedious process, and I'm wodering if there's a tool that can actually generate the Java code that corresponds to a browser session. I expect the generated code wouldn't be as pretty as code written manually, but I could always tidy it up afterwards. Does anyone know if such a tool exists? Selenium is one possibility I'm aware of, though I'm not sure if it supports this exact use case.
Thanks,
Don

I would also add +1 for HtmlUnit since its functionality is very powerful: if you are needing behaviour 'as though a real browser was scraping and using the page' that's definitely the best option available. HtmlUnit executes (if you want it to) the Javascript in the page.
It currently has full featured support for all the main Javascript libraries and will execute JS code using them. Corresponding with that you can get handles to the Javascript objects in page programmatically within your test.
If however the scope of what you are trying to do is less, more along the lines of reading some of the HTML elements and where you dont much care about Javascript, then using NekoHTML should suffice. Its similar to JDom giving programmatic - rather than XPath - access to the tree. You would probably need to use Apache's HttpClient to retrieve pages.

The manageability.org blog has an entry which lists a whole bunch of web page scraping tools for Java. However, I do not seem to be able to reach it right now, but I did find a text only representation in Google's cache here.

You should take a look at HtmlUnit - it was designed for testing websites but works great for screen scraping and navigating through multiple pages. It takes care of cookies and other session-related stuff.

I would say I personally like to use HtmlUnit and Selenium as my 2 favorite tools for Screen Scraping.

A tool called The Grinder allows you to script a session to a site by going through its proxy. The output is Python (runnable in Jython).