I'm not sure if this is possible but I would like to retrieve some data from a web page that uses Javascript to render data. This would be from a linux shell.
What I am able to do now:
http post using curl/lynx/wget to login and get headers from command line
use headers to get into 'secure' locations in the webpage on command line
However, the only elements that are rendered on the page are the static html. Most of the info I need are rendered dynamically with js (albeit eventually as a html as well) and don't show up on a command line browser. I understand the issue is with the lack of a js interpreter.
As such... some workarounds I thought might be possible are:
calling full browsers from command line and somehow passing the info back to stdout. this would mean that I have to be able to POST.
passing the headers (with session info, etc...) i got from curl to one of these full browsers and again dumping the output html back to stdout. it could very be a printscreen function on the window if all else fails.
a pure java solution would be OK too.
Anyone has any experience doing something similar and succeeding?
Thanks!
You can use WebDriver to do, just that you need have web browser installed. There are other solution as well such as Selenium and HtmlUnit (without browser but might behave differently).
You can find example of Selenium project at here.
WebDriver
WebDriver is a tool for writing automated tests of websites. It aims
to mimic the behaviour of a real user, and as such interacts with the
HTML of the application.
Selenium
Selenium automates browsers. That's it. What you do with that power is
entirely up to you. Primarily it is for automating web applications
for testing purposes, but is certainly not limited to just that.
Boring web-based administration tasks can (and should!) also be
automated as well.
HtmlUnit
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.
I would recommend use WebDriver because it is not required standalone server like Selenium, while for HtmlUnit might suitable if you dont want install browser without worry about Xvfb in headless environment.
You might want to see what Selenium can do for you. It has numerous language drivers (Java included) that can be used to interact with the browser to process content typically for testing and verification purposes. I'm not exactly sure how you can get exactly what you are looking for out of it but wanted to make you aware of its existence and potential.
This is impossible unless you setup a websocket, and even like this I guess it really depends.
Could you detail your objective? For my personal curiosity :-)
Related
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
I need to create a java program which should go to a website's login page, log in, than go to an another page of the site and submit a form. I know how to submit a form, but my problem is with the login part. This script should work with multiple sites, some are using cookies and some sessions. Is there any way to solve my problem ?
I can't show you any code because I don't know where to begin, first I should submit the login form and then separately go to the submission page ? I don't know please help me, or please tell me how could I solve this problem: I want to submit a form on various sites automatically, only I will be using this script. Until now I'we created a script in JavaScript and I'we opend the sites in iframes and I'we discovered that in Google chrome I can control external iframes, too, and I`we used JavaScript to fill the forms automatically, but my problem is that I need to submit files, images too, and I can't do this using only JavaScript. If it's not possible to do this using java please help me to find an another solution, I need to make it fully automated.
You can use Apache HTTP Client for logging in to websites using Java.
I would take a look at the Selenium RC framework and APIs. It's a test automation tool but there's no reason why you couldn't use it for doing programmatic logins to websites. It has client libraries for many languages including Java.
Using selenium RC you can write Java could thatcan load, navigate and fill in forms programmatically. You are able to target the form input fields using field names or classes and the Java API allows you to load multipart data into a form.
Selenium comes in two flavours, the older Selenium RC version and the newer WebDriver version. Both are capable of doing what you want, however they have slightly different ways of doing it. The documentation provides some good examples to get you started.
I needed a headless browser to parse pages.
HtmlUnit allow me to setup a Heroku Java app to fullfil this purpose.
But now I'm meeting with couple of issues.
The current one is malformed url "//path" instead of "/path" or "http(s)://path".
I downloaded sources of the 2.9.4 version and pushed tiny fixes in the sources ...
It's not really efficient to modify standard sources for obvious maintainability reasons.
I'm so wondering if i'm not digging in the wrong direction.
HtmlUnit is designed to browse pages in a testing purpose. Mine is to do like a browser, so make page working the most possible, especially because my damned targeted websites are the kind of ultra-dirty-not-respecting-anything...
What is your opinion about this retrospection ?
HTML Unit is used in Selenium 2/Web Driver for headless browser "simulation". There it works fine.
So I see no reason not to try Html Unit. May you can have a look at Selenium 2/Web Driver too.
I am newbie in wkhtmltopdf. I am wondering how to use wkhtmltopdf with my Dynamic Web Project in Eclipse? How to integrate wkhtmltopdf with my Java dynamic web application?
Is there any tutorials available for beginners of wkhtmltopdf ?
(Basically, I would like to use wkhtmltopdf in my web application so that when user click a save button , the current page will be saved to PDF file).
First, a technical note: Because you want to use wkhtmltopdf in a web project, if and when you deploy to a Linux server machine that you access via ssh (i.e. over the network), you will need to either use the patched Qt version, or run an X server, e.g. the dummy X server xvfb. (I don't know what happens if you deploy to a server running an operating system other than Linux.)
Second, it should be really quite simple to use wkhtmltopdf from any language in a web project.
If you just want to save the server-generated version of the current page, i.e. without any changes which might have been made like the user filling on forms, or Javascript adding new DOM elements, you just need to have an extra optional argument like ?generate=pdf on the end of your URL, which will cause that page to be generated as a PDF, and then the PDF button will link to that URL. This may be a lot of work to add to each page manually if you are just using simple JSP or something, but depending on which web framework you are using, the web framework may offer some help to implement the same action on every page, if you need to implement that.
To implement this approach, you would probably want to capture the response by wrapping the response object and overridding its getWriter() and getOutputStream() methods.
Another approach is to have a button "submit and generate PDF" which will generate the next page as a PDF. This might make more sense if you have a form the user needs to fill in - I don't know. It's a design decision really.
A third approach is to use Javascript to upload the current state of the page back to the server, and process that using wkhtmltopdf. This will work on any page. (This can even be used on any site, not just yours, if you make it a bookmarklet. Just an idea that occurred to me - it may not be a good idea.)
A fourth approach is, because wkhtmltopdf can fetch URLs, to pass the URL of your page instead of the contents of the page (which will only work if the request was a HTTP GET, or if it's equivalent to a HTTP GET on the same URL). This has some small amount of overhead over capturing your own response output, but it will probably be negligible. You will also very likely need to copy the cookie(s) into a cookie jar with this approach, since presumably your user might be logged in or have an implicit session.
So as you can see there are quite a lot of choices!
Now, the question remains: when your server has the necessary HTML, from any of the above approaches, how to feed it into wkhtmltopdf? This is pretty simple. You will need to spawn an external process using either Runtime.getRuntime().exec(), or the newer API called ProcessBuilder - see http://www.java-tips.org/java-se-tips/java.util/from-runtime.exec-to-processbuilder.html for a comparison. If you are smart about it you should be able to do this without needing to create any temporary files.
One of the wkhtmltopdf websites is currently down, but the main README is available here, which explains the command line arguments.
This is merely an outline answer which gives some pointers. If you need more details, let us know what specifically you need to know.
Additional info:
If you do end up trying to call wkhtmltopdf in an external process from java (or for that matter, any language), please note that the "normal" output that you see when using wkhtmltopdf from the command line (i.e. what you would expect to see in STDOUT) is not not in STDOUT but in STDERR. I raised this issue in the project page
http://code.google.com/p/wkhtmltopdf/issues/detail?id=825
and was replied that this is by design because wkhtmltopdf supports giving the actual pdf output in STDOUT. Please see the link for more details and java code.
java-wkhtmltopdf-wrapper provides an easy API for using wkhtmltopdf in Java.
It also works out-of-the-box on a headless server with xvfb.
E.g., on a Ubuntu or Debian server:
aptitude install wkhtmltopdf xvfb
Then in Java:
Pdf pdf = new Pdf();
pdf.addPage("http://www.google.com", PageType.url);
pdf.saveAs("output.pdf");
See the examples on their Github page for more options.
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).