Develop Reference

Can you programmatically connect to a sequence of web-pages and parse the source HTML without imposing stress on the system or raising red flags?

I am working on a project in NLP requiring me to download quite a few video game reviews --- about 10,000 per website. So, I am going to write a program that goes to each URL and pulls out the review part of each page as well as some additional metadata.
I'm using Java and was planning on just opening an HttpURLConnection and reading the text through an input stream. Then, closing the connection and opening the next one.
My questions are this:
1) Let's assume this is a site with medium-to-small amounts of traffic: normally, they receive about 1000 requests per second from normal users. Is it possible that my program would cause undue stress to their system, impacting the user experience for others?
2) Could these connections made one right after another appear as some kind of malicious attack?
Am I being paranoid, or is this an issue? Is there a better way to go about getting this data? I am going to several websites so working individually with site administrators is inconvenient and probably impossible.

If you mimic a web browser, and extract text at human speeds (that is, it normally takes a human several seconds to "click thru" to the next page even if they aren't reading the text), then the server can't really tell what the client is.
In other words, just throttle your slurping to 1 page per few seconds, and no problems.
The other concern you ought to have is legality. I assume these reviews are material that you didn't write, and have no permission to create derivative works from. If you are just slurping them for personal use, then its ok. If you are slurping them to create something (a derivative work), then you are breaking copyright.

I believe you are misunderstanding how HTTP requests work. You ask for a page and you get it... the fact that you're reading a stream one line at a time has no bearing on the HTTP request and the site is perfectly happy to give you your 1 page at a time. It won't look malicious (cause it's just 1 users reading pages... totally normal behavior). You're 100% ok to proceed with your plan (if it is as you described it).

Can page scraping be detected?

So I just created an application that does page scraping for me, and ran it. It worked fine. I was wondering if someone would be able to figure out that the code was being page scraped, whether or not they had written code for that purpose?
I wrote the code in java, and it's pretty much just checking for one line of the html code.
I thought I'ld get some insight on that before I add anymore code to this program. I mean it's useful, and all, but it's almost like a hack.
Seems like the worst case scenario as a result of this page scraper isn't too bad as I can just use another device later and the IP will be different. Also it might not matter in a month. The website seems to be getting quite a lot of web traffic anyways at the moment. Whoever edits the page is probably asleep now, and it really hasn't accomplished anything at this point so this could go unnoticed.
Thanks for such fast responses. I think it might have gone unnoticed. All I did was copy a header, so just text. I guess that is probably similar to how browser copy-paste works. The page was just edited this morning, including the text I was trying to get. If they did notice anything, they haven't announced it, so all is good.

It is a hack. :)
There's no way to programmatically determine if a page is being scraped. But, if your scraper becomes popular or you use it too heavily, it's quite possible to detect scraping statistically. If you see one IP grab the same page or pages at the same time every day, you can make an educated guess. Same if you see requests on another timer.
You should try to obey the robots.txt file if you can, and rate limit yourself, to be polite.

As a sysadmin myself, yes I'd probably notice but ONLY based on the behavior of the client. If a client had a weird user agent, I'd be suspicious. If a client browsed the site too quickly or in very predictable intervals, I'd be suspicious. If certain support files were never requested (favicon.ico, various linked in CSS and JS files), I'd be suspicious. If the client were accessing odd (not directly accessible) pages, I'd be suspicious.
Then again I'd have to actually be looking at my logs. And this week Slashdot has been particularly interesting, so no I probably wouldn't notice.

It depends on how have you implemented this and how smart are the detection tools.
First take care about User-Agent. If you do not set it explicitly it will be something like "Java-1.6". Browsers send their "unique" user agents, so you can just mimic the browser behavior and send User-Agent of MSIE, or FireFox (for example).
Second, check other HTTP headers. Probably some browsers send their specific headers. Take one example and follow it, i.e. try to add the headers to your requests (even if you do not need them).
Human user acts relatively slowly. Robot may act very quickly, i.e. retrieve the page and then "click" link, i.e. perform yet another HTTP GET. Put random sleep between these operations.
Browser retrieves not only the main HTML. Then it downloads images and other stuff. If you really do not want to be detected you have to parse HTML and download this stuff, i.e. actually be "browser".
And the last point. It is obviously not your case but it is almost impossible to implement robot that passes Capcha. This is yet another way to detect robot.
Happy hacking!

If your scraper acts like a human then there is a hardly any chance for it to be detected as a scraper. But if your scraper acts like a robot then its not difficult to be detected.
To act like a human you will need to:
Look at what a browser sends in the HTTP headers and simulate them.
Look at what a browser requests for when accessing the page and access the same with the scraper
Time your scraper to access at the speed of a normal user
Send requests at random intervals of time instead of at fixed intervals
If possible make requests from a dynamic IP rather than a static one

assuming you wrote the page scraper in a normal manner, i.e., it fetches the whole page and then does pattern recognition to extract what you want from the page, all someone might be able to tell is that the page was fetched by a robot rather than a normal browser. all their logs will show is that the entire page was fetched; they can't tell what you do with it once it's in your RAM.

To the server serving the page, there's no difference whether you download a page into the browser or download a page and screen scrape it. Both actions just require an HTTP request, whatever you do with the resulting HTML on your end is none of the server's business.
Having said that, a sophisticated server could conceivably detect activity that doesn't look like a normal browser. For example, a browser should request any additional resources linked to from the page, something that usually doesn't happen when screen scraping. Or requests with an unusual frequency coming from a particular address. Or simply the HTTP User-Agent header.
Whether a server tries to detect these things or not depends on the server, most don't.

I'd like to put my two cents in for others that may be reading this. In the past couple of years web scraping has been frowned upon more and more by the court system. I've cited a lot of examples in a blog post I recently wrote.
You should definitely abide the robots.txt but also look at the websites T&C's to make sure you are not in violation. There are definitely ways that people can identify you are web scraping and there could be potential consequences for doing so. In the event that web scraping is not disallowed by the website's Terms and Conditions, then have fun but make sure to still be conscionable. Dont destroy a webserver with an out of control bot, throttle yourself to make sure you dont impact the server!
For full disclosure, I am a co-founder of Distil Networks and we help companies identify and stop web scrapers and bots.

Parsing a HTML file in Java

I am currently in the process of developing an application that will request some information from Websites. What I'm looking to do is parse the HTML files through a connection online. I was just wondering, by parsing the Website will it put any strain on the server, will it have to download any excess information or will it simply connect to the site as I would do through my browser and then scan the source?
If this is putting extra strain on the Website then I'm going to have to make a special request to some of the companies I'm scanning. However if not then I have the permission to do this.
I hope this made some sort of sense.
Kind regards,
Jamie.

No extra strain on other people servers. The server will get your simple HTML GET request, it won't even be aware that you're then parsing the page/html.
Have you checked this: JSoup?

Consider doing the parsing and the crawling/scraping in separate steps. If you do that, you can probably use an existing open-source crawler such as crawler4j that already has support for politeness delays, robots.txt, etc. If you just blindly go grabbing content from somebody's site with a bot, the odds are good that you're going to get banned (or worse, if the admin is feeling particularly vindictive or creative that day).

Depends on the website. If you do this to Google then most likely you will be on a hold for a day. If you parse Wikipedia, (which I have done myself) it won't be a problem because its already a huge, huge website.
If you want to do it the right way, first respect robots.txt, then try to scatter your requests. Also try to do it when the traffic is low. Like around midnight and not at 8AM or 6PM when people get to computers.

Besides Hank Gay's recommendation, I can only suggest that you can also re-use some open-source HTML parser, such as Jsoup, for parsing/processing the downloaded HTML files.

You could use htmlunit. It gives you virtual gui less browser.

Your Java program hitting other people's server to download the content of a URL won't put any more strain on the server than a web browser doing so-- essentially they're precisely the same operation. In fact, you probably put less strain on them, because your program probably won't be bothered about downloading images, scripts etc that a web browser would.
BUT:
if you start bombarding a server of a company with moderate resources with downloads or start exhibiting obvious "robot" patterns (e.g. downloading precisely every second), they'll probably block you; so put some sensible constraints on what you do (e.g. every consecutive download to the same server happens at random intervals of between 10 and 20 seconds);
when you make your request, you probably want to set the "referer" request header either to mimic an actual browser, or to be open about what it is (invent a name for your "robot", create a page explaining what it does and include a URL to that page in the referer header)-- many server owners will let through legitimate, well-behaved robots, but block "suspicious" ones where it's not clear what they're doing;
on a similar note, if you're doing things "legally", don't fetch pages that the site's "robot.txt" files prohibits you from fetching.
Of course, within some bounds of "non-malicious activity", in general it's perfectly legal for you to make whatever request you want whenever you want to whatever server. But equally, that server has a right to serve or deny you that page. So to prevent yourself from being blocked, one way or another, you need to either get approval from the server owners, or "keep a low profile" in your requests.

What sort of encoding/image/formatting issues are there when building a web mail client that pulls emai via pop3

What sort of encoding/image/formatting issues are there when building a web mail client that pulls emai via pop3?
Some things i can think of that I know I will have to handle:
attachments
inline images
html emails
What other possible headaches are there?

It's quite a lot of work, and there are already a lot of solutions out there - but that shouldn't deter you! Your three points cover almost everything in general terms... the fact it's coming through POP3 isn't all that relevant, IMAP, or even OWS (Outlook Web Services for Exchange) all require attention to the following points:
Attachments can be referred to inline in an email (combo of your 1,2,3) - as in an email can include an IMAGE which is itself an attachment.
There are many MIME types you have to support.
Emails can be a single part, multi-part different, multi-part alternative, and combinations thereof. A good newsletter will send you a text & HTML version of the same data leaving the client the choice to choose which way to consume the data. That email could have one or more attachments... and that attachment can be another text/html email with another attachment... and this goes on ad nauseam.
HTML As you've already pointed out, rendering email HTML inside your page without intersects in style etc is tricky, plus you'll want to filter for bad content - JavaScript includes potentially, embedded images which might have privacy implications.
There are several character encodings that can be used - this ties into MIME types, but is worth independently noting (for headache-worthiness alone).
Basically you have to be jack of a number of trades to generate and decode emails.

Many !
I highly suggest you to read the pop3 rfc as a starter.
http://www.faqs.org/rfcs/rfc1939.html
You can download few open source projects to see how they implemented the rfc's.

I agree with Pierre that you should read the specs to fully understand what's going on behind the scenes.
One thing I would add though is that the key thing I would be worried about is the security of the mailboxes you are reading and SPAM. Emails often contain calls to javascript/images that can be used to track whether the message has been opened. This is the key reason many mail client don't show images unless you turn them on.
Along with the other methods you are using you will probably have to make sure you parse the message and take out any calls that could potentially cause privacy issues unless the senders are trusted.

Access Hotmail Unread Mail Count via Java

I want to write an application using Java6 that can check a users Hotmail inbox for the 'unread message count'!
There is a Javascript API but I will not have a browser instance, and it seems that I need one to use it. (see stakoverflow question: 964392 )
I can use POP3, but since it does not support flags, I can only tell how many 'new' messages there are in the users Inbox since the last time I checked, not how many unread messages there are. ( This is my current implementation, it's not what is required, but is currently all I can achieve )
There is IMAP access, but only for 'premium users'(Hotmail users who pay).
There's also HttpMail access, but this is poorly documented, and from testing, seems it's also only for premium users.

Unfortunately, this similar question on msdn suggests this is impossible
EDIT:
All I can offer is a half-solution. You could create the html page containing the script suggested by the people on MSDN but instead of setting the value of an input box to the number of unread messages - you could use Ajax to post this number back to your application. This is, of course, not a very robust solution since it depends on the browser and may very well not be cross platform. Another thing you can do is read up on running Javascript on the JVM. I don't know how good that solution is, either, but I think it's more robust once (or rather if) you can get it to work.

One potential option could be to use the HTMLUnit Java headless web browser to make the requests. HTMLUnit has very good, but not perfect, JavaScript support to handle creating the dynamic content.