I have a SharePoint web part that gets XML data from an .ASHX page, parses it and displays it using JavaScript. Everything works fine, until the XML changes. When I view the web part in IE, the new data is not updated until I close the browser. Even doing a CTRL-F5 does not grab the new data.
Firefox displays the new data immediately, with just a simple page refresh.
I have added a timestamp to the query string of my .ASHX page so that the XML result is not cached, but that did not fix my IE woes. Any other ideas?
Edit
The .ASHX page is using the API to access a list and is building the XML string, then returning that as an application/XML content type. I have confirmed that the XML is updated to reflect the new data in the list. I am also able to see the data consumed in the web part when it is displayed in FireFox.
Solution
I actually was generating the timestamp to append to my query in the server code, and then putting that string in the javascript. Once I moved the timestamp code to the javascript, things started working much better.
It's most likely cached, there's no other logical explanation why it would work in Firefox and not in IE. Try reloading IE several times in a row.
Check what headers that .ashx page sets.
It's not just your browser which could be caching the page, any middleware including web server might have a flawed caching implementation. You can also try using HTTP POST instead of GET because according to HTTP specification, POST requests should never be cached.
Is it a custom Web Part or one of the out-of-the-box Web Parts? It would make it easier to help you if you provided any more information on how you're retrieving the data from the HttpHandler (ashx).
Related
I have a Windows Phone 8 app. My app needs to POST some data to a web page that I have on my server. Please note, I am trying to POST to a web page, not a web service. The reason that I need to POST to a web page is because 1) I'm trying to render some contents in a web page that is currently launched via a WebBrowserTask 2) I am passing a large amount of data to the web page.
From what I can tell, the WebBrowserTask only allows "GET". Now, I'm totally lost in regards to what to do. Is there a was to POST data via a WebBrowserTask? If not, is there a way to serialize my data as JSON and cram it into the query string? I know that's ugly. At the same time, I'm not sure what else to do.
Thank you
Try adding a WebBrowser control then make your request through either WebClient or HttpWebRequest. Once you get the html response use the NavigateToString(string) method to display the result.
But you can simply use the Navigate(uri) method if you only need to specify some query string params.
I created a userscript for myself which is active on all webpages i visit. It sends data to my debugger/app via jquery's post ($.post).
I notice one site not allowing me to send data even though it worked before and after a quick look it appears there is some kind of error via xhr-src. It appears the response headers has a 'X-Content-Security-Policy' which list a bunch of sites (google being one). So when i try to do a post to localhost:myport/ it violates the rule thus doesn't post.
What can I do to get this working again? I can't exactly edit the headers (unless i write my own http proxy?) would i be able to create an iframe using localhost:1234/workaround and post via that? But the issue is i still dont know if thats a violation or how to give it data.
How can I perform a post through the chrome extention, lets say I want to send the current tab page title to a webpage
You can do POST XHRs from chrome extensions to any URL, as long as you have host permissions defined in your manifest. See these docs.
In a chrome extension the best way to try and do what i think you want is via a content script see documentation a word of warning however pinging your server with a POST request every time someone with your extension installed opens a web page is going to be extremely heavy going on your servers especially if you have a lot of installs. A possible solution is to use the content script to keep tally of the sites a user visits and save this data in a HTML5 database (wich chrome supports) then using background.html sending the data at given intervals in bulk with an AJAX request, this will significantly cut down the number of times your server is pinged.
I'm trying to write a userscript/Chrome extension to capture JSON data being sent while using a web service so that I can reformat it and display selected portion on page. Currently the JSON is sent as the application loads (as I've observed from watching traffic with Fiddler 2). Is my only option to request the JSON again or is capture possible? As I'm not providing a code example, a requested answer is even some guidance on what method / topic to research or if I'm barking up the wrong tree.
No easy way.
If it is for a specific site you might look into intercepting and overwriting part of a code which sends a request. For example if it is sent on a button click you can replace existing click handler with your own implementation.
You can also try to make a proxy for XMLHttpRequest. Not sure if this even possible, never seen a working example. You can look at some attempts here.
For all these tasks you probably would need to run your javascript code out of sandboxed content script to be able to access parent page variables, so you would need to inject <script> tag with your code right into the page from a content script:
This is a dangerously easy thing I feel I should know more about - but I don't, and can't find much around.
The question is: How exactly does a browser know a web page has changed?
Intuitively I would say that F5 refreshes the cache for a given page, and that cache is used for history navigation only and has an expiration date - which leads me to think the browser never knows if a web page has changed, and it just reloads the page if the cache is gone --- but I am sure this is not always the case.
Any pointers appreciated!
Browsers will usually get this information through HTTP headers sent with the page.
For example, the Last-Modified header tells the browser how old the page is. A browser can send a simple HEAD request to the page to get the last-modified value. If it's newer than what the browser has in cache, then the browser can reload it.
There are a bunch of other headers related to caching as well (like Cache-Control). Check out: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
Don't guess; read the docs. Here's a friendly, but authoritative introduction to the subject.
Web browsers send HTTP requests, and receive HTTP responses. They then displays the contents of the HTTP responses. Typically the HTTP responses will contain HTML. And many HTML elements may need new requests to receive the various parts of the page. For example each image is typically another HTTP request.
There are HTTP headers that indicate if a page is new or not. For example the last modified date. Web browsers typically use a conditional GET (conditional header field) or a HEAD request to detect the changes. A HEAD request receives only the headers and not the actual resource that is requested.
A conditional GET HTTP request will return a status of 304 Not Modified if there are no changes.
The page can then later change based on:
User input
After user input, changes can happen based on javascript code running without a postback
After user input, a new request to the server and get a whole new (possibly the same) page.
Javascript code can run once a page is already loaded and change things at any time. For example you may have a timer that changes something on the page.
Some pages also contain HTML tags that will scroll or blink or have other behavior.
You're getting along the right track, and as Jonathan mentioned, nothing is better than reading the docs. However, if you only want a bit more information:
There are HTTP response headers that let the server set the cacheability of a page, which falls into your expiration date system. However, one other important construct is the HTTP HEAD request, which essentially retrieves the MIME Type and Content-Length (if available) for a given page. Browsers can use the HEAD request to validate what is in their caches...
There is definitely more info on the subject though, so I would suggest reading the docs...