I have recently created an application where a lot of data is loaded into objects when the application starts up, and other data as it is required. For example if the user requests the catalogue page then it will load all the top level category data into objects of type Category. This will then stay there to be used by other users (who will therefore not have to load this data into objects) and can be altered by admin if they happen to login during the same application instance. I know this is not the most efficient solution, as pointed out below, but it works and the page load, at the moment, is not too long. It is very quick if most of the required data is already loaded into objects. It is also tailored to the business' needs - unlike other techniques such as Linq-to-SQL.
The problem I am facing is when a page is requested which requires lots of data to be displayed about different types of object. For example when a catalogue page is requested which displays information on a product which can be bought, it then loads all the products and categories (as the products make reference to the category object, not just the category name).
I would like to display a loading symbol with a message whilst all this data is being loaded into objects, so the user knows its not just in a loop or anything. Is there any way to do this? I am open to using JS / jQuery if I need to.
Thanks in advance.
Regards,
Richard
PS I am working on ways to make it more efficient - such as using HashTables or HashMaps. However this is taking time as there are so many different types of item (News, Events, Catalogue Item - Range, Collection, Design, RangeCollection, CollectionDesign, RangeCollectionDesign and RangeDesign - Users, PageViews and the list goes on).
Please correct me if I'm wrong, but I do believe that Javascript is required in order to display a "loading" image... Using server-side scriping alone would typically require an entire page load after all the content loads unless you want to start messing with IFrames.
This is a job for AJAX. A common solution to your problem is to have a small page that displays a loading icon. The page has some JavaScript that makes additional HTTP requests to the server to download the rest of the page. JQuery has a "$.ajax" method that is designed to simplify this process.
I would suggest looking at the documentation to the .ajax method in the jQuery documentation. Unfortunately, it seems to be a rather delicate process to get all the scripting code right and it takes a while to learn it all.
Related
I am trying to pull pricing data from a website, but each time the page is loaded, thet class is regenerated to a different sequence of letters, and the price is showing instead of a number. Is there a technique that I can use to bypass this in any way? Thanks! Here is the line of html as how it appears when I inspect the element:
<div class="zlgJQq">$</div>
<div class="qFwqmC hkVukg2 njGalW"> </div>
Your help would be much appreciated!
Perhaps that website is actively discouraging you from scraping their data. That would explain the apparently random class names. You might want to read their terms of use to be sure that it's OK to scrape their site.
However, if the raw HTML does not contain the price data but it is visible when the page is rendered, then it's likely that Javascript is being used to insert the prices after the page has loaded. You could try enabling the developer tools in your browser and monitoring the network activity while the page is loading. That might reveal that the site is using dynamic Ajax queries to populate the price data, and you could then write code to interact with the Ajax resource directly.
It's also possible that the price data is embedded somewhere in the HTML, possibly obfuscated, and then loaded dynamically by javascript.
That's just a couple of suggestions. You will need to analyse the site to see whether automated scraping is feasible. If you can let us know what website you're dealing with then someone might be able to suggest something more specific.
I'm looking to get structured article data from webpage urls. So far I've found these two services http://www.diffbot.com/ and http://embed.ly/extract/demos/nlp. Are there better alternatives or is it worthwhile to write the code to do this myself?
If you'd like to skip the code, and are looking for a simple software for web scraping / ETL applications, I'd suggest Foxtrot. It's easy enough to use and doesn't require coding. I use it to scrape data from certain gov't websites and dump it into an Excel spreadsheet for reporting purposes.
I have done web scraping / content extract for quite some time now.
For me the best approach is to write a Chrome content extension and automate the browser with their API. This requires that you know Javascript and HTML. In one of my recent projects I use a background page with a couple of editable divs to configure the scraping session. I have some buttons on the background page to start the process. The background page loads a JS script which listens to click events of the buttons.
When one of the buttons is clicked I add a new tab for the scraping session with chrome.tab.create. The background js also defines some chrome.tabs.onUpdated.addListener to inject content scripts when the tab url contains a specific page/domain name.
The content script then does the scraping job for example selecting some elements with jquery, regular expressions etc and finally send a message with an object back to background JS using chrome.runtime.sendmessage. The background JS script listens to messages with chrome.runtime.onMessage.addListener and acts based on the content being extracted.
The extension also automates web databases by clicking for example the next page links.
I have added a timing setting to control the amount of links being clicked / tabs being opened per minute so that the access is slowed down on purpose and too much crawling is avoided.
Finally the results are being uploaded to a database with an AJAX call and inserted with a PHP page into MySQL.
When the extension runs the next time it compares the keys/links which already exist in the database with another AJAX call and ensures that only new information is being extracted.
I have also built extension like the above with Firefox but the best and easiest solution for me is a Chrome/Chromium content extension.
We have a Google Spreadsheet from which we wish to load data into our webpage.
I started by using the Google Spreadsheet APi via C# and the Google API .NET libraries to read the spreadsheet and load it into an html unsorted list.
The spreadhsheet has about 200 rows, but could have more, as it will be updated frequently. So the problem is that the users have to wait until the spreadsheed data is retrieved and parsed before they can see anything in the webpage (the page is white whilst loading).
How can I load this data in the background whilst the page loads?
I've already written my code in C# and don't much want to spend the time swapping to javascript, but I will if I have to.
Could I use the AJAX Control Toolkit to do this? I know it will load html, but can I use it to fetch google data?
What can I do here that would be fast and easy?
[Edit]
The account that hosts the google spreadsheet is inside a google domain, so it's documents can't be shared to the public as a whole - only to individuals. The C# libraries allow me to use the account's username and password to log into the account to get the spreadsheet data, and so the spreadsheet doesn't need to be shared at all. Even if I went with a javascript/ajax solution, I would yet need this functionality.
Well, this probably isn't the BEST answer, but it IS a solution. I'd like to see if y'all have a better one.
Anyway, I found this, which is an example of how to use an asp:Timer to delay the calling of a function for a certain amount of time - in my case, long enough for the page itself to load. At least this way, the user gets to see the page, and can watch the nice loading-gif until the actual content arrives.
It is an AJAXy approach that allows me to keep my c# programming without having to add any javascript.
I'm building a website that on its frontpage has different 'lists' of stories/articles.
You can compare it to Wordpress 'latest articles', 'spotlight articles' etc.
Now every list needs to be created, and filled from the repository.
Which means, that in my controller, I first create/retrieve all the lists, add them to the ViewBag, and then return the view.
In the View i'll then foreach over the items in that list to create a visual list to be shown on the frontpage.
However, when I load the page, I first get a blank page, when the page is loaded, and then at one point everything appears.
Traditionally, you would already see the basic html, text etc, and then the dynamic area's would appear later.
Is it possible to have a similar 'progressive loading' with MVC3?
Its not so much the performance I'm worrying about but more so the user experience of seeing a blank page for several seconds on data-heavy pages.
Thanks :)
If you've got heavy pages with long loading times you might consider loading the pieces more dynamically using an ajax approach.
Your page loads, you execute the requests for the data you require and use some standard loading icon in the meantime.
I have a grid with several thousand rows that can be filtered and sorted. On each row you can click a details button, which will bring you a new page with detailed information about the page. Because this is a button, you can't middle click or right click and open in a new tab. In addition, when clicking back you lose your filters and search results.
To solve this problem, I considered the following: Switch the buttons to links, and when filtering and searching, use get instead of post requests. This way, you could switch to new pages with a right click or middle click, and if you did follow a link normally, back would work properly.
This change was not made however. We were asked add a 'next result / previous result' set of buttons on the details page, that would allow you to navigate. While not an elegant solution, it would at least work.
I proposed adding querystring parameters to the details page, that would regenerate the search query based on filter, and allow you to get the next and previous results in code.
A team member took issue with this solution. He believes that it is a waste of server resources to re-query the database. Instead, a solution was proposed to add session variable that included a list of results. You could then use that to navigate.
I took issue with that because you can't have multiple tabs open without breaking navigation, and new results aren't appended to the list in real time. Also, if you worried about optimization, session would be the last thing to use since it eats memory and prevents server replication... unless you store the results back in the database.
What's the best solution?
Session doesn't sound like a winner, won't scale with lots of users.
Hitting the database repeatedly does seem unnecessary, but it depends on the cost - how many users, how often would they refresh/filter and what is the cost of that query?
If you do use querystrings you could cache the pages by parameter.
What about some AJAX code on that button to retrieve details - leave the underlying grid in place and display details in a div/panel or a new window/tab.