I use an html table where it's content can be changed with mouse drag and drop implemented. Technically, you can move the data from any table cell to another. The table size 50 row * 10 column with each cell given a unique identifier. I want to export it to .xlsx format with C# EPPlus library, and give back the exported file to client.
So I need the pass the whole table data upon a button press and post it to either a web api or an mvc controller, create an excel file (like the original html table data) and send it back to download with browser.
So the idea is to create an array which contains each of table cell's value ( of course there should be empty cells in that array), and post that array to controller.
The problem with that approach lies in the download, if I call the api or mvc controller with regular jquery's ajax.post it did not recognize the response as a file.
C# code after ajax post:
[HttpPost]
public IHttpActionResult PostSavedReportExcel([FromBody]List<SavedReports> savedReports, [FromUri] string dateid)
{
//some excel creation code
HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StreamContent(new MemoryStream(package.GetAsByteArray()))
};
response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
{
FileName = dateid + "_report.xlsx"
};
ResponseMessageResult responseMessageResult = ResponseMessage(response);
return responseMessageResult;
}
Usually, for this kind of result I could use window.location = myurltocontroller to download properly , but that is only for GET requests, POST anything is not possible.
I found some answers which could help me in this topic:
JavaScript post request like a form submit
This points out I should go with creating a form, which passes the values, but I do not know how to do so in case of arrays (the table consists 50*10 = 500 values which I have to pass in the form)
I tried some only frontend solutions to the html-excel export problem, which of course does not require to build files on api side, but free jquery add-ins are deprecated, not customizeable, handle only .xls formats, etc.
I found EPPlus nuget package a highly customizeable tool, that is why I want to try this is at first place.
So the question is: how can I post an array of 500 elements, that the controller will recognize, generate the file, and make it automatically download from browser?
If you can provide some code that would be fantastic, but giving me the right direction is also helpful.
Thank you.
You can use fetch() (docs) to send the request from the JS frontend. When the browser (JS) has received the response, it can then offer its binary content as a download. Something like this:
fetch("http://your-api/convert-to-excel", // Send the POST request to the Backend
{
method:"POST",
body: JSON.stringify(
[[1,2],[3,4]] // Here you can put your matrix
)
})
.then(response => response.blob())
.then(blob => {
// Put the response BLOB into a virtual download from JS
if (navigator.appVersion.toString().indexOf('.NET') > 0) {
window.navigator.msSaveBlob(blob, "my-excel-export.xlsx");
} else {
var a = window.document.createElement('a');
a.href = URL.createObjectURL(blob);
a.download = "my-excel-export.xlsx";
a.click();
}});
So the JS part of the browser actually first downloads the file behind the scenes, and only when it's done, it's triggering the "download" from the browsers memory into a file on the HD.
This is a quite common scenario with REST APIs that require bearer token authentication.
I've an object created in javacript with a lot of data and I serialize it to JSON to send it to the server. After this, the server must do somework and create a dynamic file, so it can be downloaded.
For the last routine I created an ASHX but can be modified. Already I'm getting a "httpcontext" that I found in another question how to work with it to get the data from the JSON, so my question is not related about this.
The problem (more oriented to JS) is this one:
How can I sent the JSON to the ASHX as a URL/GET/POST to the generic handler to avoid the "ajax reply" and be the user open a new window with the link dinamically generated?
Thanks, sorry for my english (please edit) and kind regards!
Note 1: I can't use third-part code
Note 2: I can't use JSON.NET
Note 3: I can't save the report on the server so the response must be a generated file to download, even more, the download itself is the response of the server.
---UPDATE----
I've been read this question:
Can I post JSON without using AJAX?
The only thing I don't understand from that question is how to make it work, thinking in that I've a "link" to download
I assume you do not want to refresh the whole page so there is a workaround.
1) Ajax-load an iframe which is a separate aspx file for example.
2) In the codebehind of that separate aspx file, generate the file in memory and convert it to an array of bytes.
3) Then use Response to stream the bytes to the user.
Finally I resolved the issue with this (in the right way).
I just take my json object and send it trough POST with a dynamic form generated with javfascript
var dataToPostInExport = JSON.stringify(queryToVerify);
//Convert To POST and send
var VerifyForm = document.createElement("form");
VerifyForm.target = "_blank";
VerifyForm.method = "POST";
VerifyForm.action = "file.ashx";
var dataInput = document.createElement("input");
dataInput.type = "hidden";
dataInput.name = "mydata";
dataInput.value = dataToPostInExport;
VerifyForm.appendChild(dataInput);
document.body.appendChild(VerifyForm);
VerifyForm.submit();
Then in the ashx file:
Dim DataToParse As String
DataToParse = HttpContext.Current.Request.Form("mydata")
Dim JSSerializer As New JavaScriptSerializer
Dim QueryToExport as my very own type!
QueryToExport = JSSerializer.Deserialize(Of My Own Type)(dataToParse)
I have a .js script that sends data to a .py script running on the local host.
To send data from the .js, I have the following work around (to deal with the limitations of XmlHTTPRequest):
var req = document.createElement("img");
req.src = "http://0.0.0.0:8000?var="+data
To recieve it on the python end:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(5)
conn, addr = s.accept()
data = conn.recv(1024)
conn.close()
print data
This works fine, but my problem is that the char limit on a GET prevents me from sending all of the data I need. I tried making to URI GET requests (using the first block of code twice), but my python only recieved the first request. How can I send/recieve mulitple GET requests? I am assuming I will need some sort of loop, but am unsure what steps need to be in the loop.
From your Python code, it doesn't seem like the HTTP request method used makes any difference. In that case, I'd recommend setting up a form element with method="post" and just putting whatever you want in it. There's no theoretical limit on post body length.
I am working on creating a RESTful API that supports cross-domain requests, JSON/JSONP support, and the main HTTP method (PUT/GET/POST/DELETE). Now while will be easy to accessing this API through server side code , it would nice to exposed it to javascript. From what I can tell, when doing a JSONP requests with jQuery, it only supports the GET method. Is there a way to do a JSONP request using POST/PUT/DELETE?
Ideally I would like a way to do this from within jQuery (through a plugin if the core does not support this), but I will take a plain javascript solution too. Any links to working code or how to code it would be helpful, thanks.
Actually - there is a way to support POST requests.
And there is no need in a PROXI server - just a small utility HTML page that is described bellow.
Here's how you get Effectively a POST cross-domain call, including attached files and multi-part and all :)
Here first are the steps in understanding the idea, after that - find an implementation sample.
How JSONP of jQuery is implemented, and why doesn't it support POST requests?
While the traditional JSONP is implemented by creating a script element and appending it into the DOM - what results inforcing the browser to fire an HTTP request to retrieve the source for the tag, and then execute it as JavaScript, the HTTP request that the browser fires is simple GET.
What is not limited to GET requests?
A FORM. Submit the FORM while specifing action the cross-domain server.
A FORM tag can be created completely using a script, populated with all fields using script, set all necessary attributes, injected into the DOM, and then submitted - all using script.
But how can we submit a FORM without refreshing the page?
We specify the target the form to an IFRAME in the same page.
An IFRAME can also be created, set, named and injected to the DOM using script.
But How can we hide this work from the user?
We'll contain both FORM and IFRAME in a hidden DIV using style="display:none"
(and here's the most complicated part of the technique, be patient)
But IFRAME from another domain cannot call a callback on it's top-level document. How to overcome that?
Indeed , if a response from FORM submit is a page from another domain, any script communication between the top-level page and the page in the IFRAME results in "access denied". So the server cannot callback using a script. What can the server can do? redirect. The server may redirect to any page - including pages in the same domain as the top-level document - pages that can invoke the callback for us.
How can a server redirect?
two ways:
Using client side script like <Script>location.href = 'some-url'</script>
Using HTTP-Header. See: http://www.webconfs.com/how-to-redirect-a-webpage.php
So I end up with another page? How does it help me?
This is a simple utility page that will be used from all cross-domain calls. Actually, this page is in-fact a kind of a proxi, but it is not a server, but a simple and static HTML page, that anybody with notepad and a browser can use.
All this page has to do is invoke the callback on the top-level document, with the response-data from the server. Client-Side scripting has access to all URL parts, and the server can put it's response there encoded as part of it, as well as the name of the callback that has to be invoked. Means - this page can be a static and HTML page, and does not have to be a dynamic server-side page :)
This utility page will take the information from the URL it runs in - specifically in my implementation bellow - the Query-String parameters (or you can write your own implementation using anchor-ID - i.e the part of a url right to the "#" sign). And since this page is static - it can be even allowed to be cached :)
Won't adding for every POST request a DIV, a SCRIPT and an IFRAME eventually leak memory?
If you leave it in the page - it will. If you clean after you - it will not. All we have to do is give an ID to the DIV that we can use to celan-up the DIV and the FORM and IFRAME inside it whenever the response arrives from the server, or times out.
What do we get?
Effectively a POST cross-domain call, including attached files and multi-part and all :)
What are the limits?
The server response is limited to whatever fits into a redirection.
The server must ALWAYS return a REDIRECT to a POST requests. That include 404 and 500 errors.
Alternatively - create a timeout on the client just before firing the request, so you'll have a chance to detect requests that have not returned.
not everybody can understand all this and all the stages involved. it's a kind of an infrastructure level work, but once you get it running - it rocks :)
Can I use it for PUT and DELETE calls?
FORM tag does not PUT and DELETE.
But that's better then nothing :)
Ok, got the concept. How is it done technically?
What I do is:
I create the DIV, style it as invisible, and append it to the DOM. I also give it an ID that I can clean it up from the DOM after the server response has arrived (the same way JQuery cleans it's JSONP SCRIPT tasgs - but the DIV).
Then I compose a string that contains both IFRAME and FORM - with all attributes, properties and input fields, and inject it into the invisible DIV. it is important to inject this string into the DIV only AFTER the div is in the DOM. If not - it will not work on all browsers.
After that - I obtain a reference to the FORM and submit it.
Just remember one line before that - to set a Timeout callback in case the server does not respond, or responds in a wrong way.
The callback function contains the clean-up code. It is also called by timer in case of a response-timeout (and cleans it's timeout-timer when a server response arrives).
Show me the code!
The code snippet bellow is totally "neutral" on "pure" javascript, and declares whatever utility it needs. Just for simplification of explaining the idea - it all runs on the global scope, however it should be a little more sophisticated...
Organize it in functions as you may and parameterize what you need - but make sure that all parts that need to see each other run on the same scope :)
For this example - assume the client runs on http://samedomain.com and the server runs on http://crossdomain.com.
The script code on the top-level document
//declare the Async-call callback function on the global scope
function myAsyncJSONPCallback(data){
//clean up
var e = document.getElementById(id);
if (e) e.parentNode.removeChild(e);
clearTimeout(timeout);
if (data && data.error){
//handle errors & TIMEOUTS
//...
return;
}
//use data
//...
}
var serverUrl = "http://crossdomain.com/server/page"
, params = { param1 : "value of param 1" //I assume this value to be passed
, param2 : "value of param 2" //here I just declare it...
, callback: "myAsyncJSONPCallback"
}
, clientUtilityUrl = "http://samedomain.com/utils/postResponse.html"
, id = "some-unique-id"// unique Request ID. You can generate it your own way
, div = document.createElement("DIV") //this is where the actual work start!
, HTML = [ "<IFRAME name='ifr_",id,"'></IFRAME>"
, "<form target='ifr_",id,"' method='POST' action='",serverUrl
, "' id='frm_",id,"' enctype='multipart/form-data'>"
]
, each, pval, timeout;
//augment utility func to make the array a "StringBuffer" - see usage bellow
HTML.add = function(){
for (var i =0; i < arguments.length; i++)
this[this.length] = arguments[i];
}
//add rurl to the params object - part of infrastructure work
params.rurl = clientUtilityUrl //ABSOLUTE URL to the utility page must be on
//the SAME DOMAIN as page that makes the request
//add all params to composed string of FORM and IFRAME inside the FORM tag
for(each in params){
pval = params[each].toString().replace(/\"/g,""");//assure: that " mark will not break
HTML.add("<input name='",each,"' value='",pval,"'/>"); // the composed string
}
//close FORM tag in composed string and put all parts together
HTML.add("</form>");
HTML = HTML.join(""); //Now the composed HTML string ready :)
//prepare the DIV
div.id = id; // this ID is used to clean-up once the response has come, or timeout is detected
div.style.display = "none"; //assure the DIV will not influence UI
//TRICKY: append the DIV to the DOM and *ONLY THEN* inject the HTML in it
// for some reason it works in all browsers only this way. Injecting the DIV as part
// of a composed string did not always work for me
document.body.appendChild(div);
div.innerHTML = HTML;
//TRICKY: note that myAsyncJSONPCallback must see the 'timeout' variable
timeout = setTimeout("myAsyncJSONPCallback({error:'TIMEOUT'})",4000);
document.getElementById("frm_"+id+).submit();
The server on the cross-domain
The response from the server is expected to be a REDIRECTION, either by HTTP-Header or by writing a SCRIPT tag. (redirection is better, SCRIPT tag is easier to debug with JS breakpoints).
Here's the example of the header, assuming the rurl value from above
Location: http://samedomain.com/HTML/page?callback=myAsyncJSONPCallback&data=whatever_the_server_has_to_return
Note that
the value of the data argument can be a JavaScript Object-Literal or JSON expression, however it better be url-encoded.
the length of the server response is limited to the length of a URL a browser can process.
Also - in my system the server has a default value for the rurl so that this parameter is optional. But you can do that only if your client-application and server-application are coupled.
APIs to emit redirection header:
http://www.webconfs.com/how-to-redirect-a-webpage.php
Alternatively, you can have the server write as a response the following:
<script>
location.href="http://samedomain.com/HTML/page?callback=myAsyncJSONPCallback&data=whatever_the_server_has_to_return"
</script>
But HTTP-Headers would be considered more clean ;)
The utility page on the same domain as the top-level document
I use the same utility page as rurl for all my post requests: all it does is take the name of the callback and the parameters from the Query-String using client side code, and call it on the parent document. It can do it ONLY when this page runs in the EXACT same domain as the page that fired the request! Important: Unlike cookies - subdomains do not count!! It has to he the exact same domain.
It's also make it more efficient if this utility page contains no references to other resources -including JS libraries. So this page is plain JavaScript. But you can implement it however you like.
Here's the responder page that I use, who's URL is found in the rurl of the POST request (in the example: http://samedomain.com/utils/postResponse.html )
<html><head>
<script type="text/javascript">
//parse and organize all QS parameters in a more comfortable way
var params = {};
if (location.search.length > 1) {
var i, arr = location.search.substr(1).split("&");
for (i = 0; i < arr.length; i++) {
arr[i] = arr[i].split("=");
params[arr[i][0]] = unescape(arr[i][1]);
}
}
//support server answer as JavaScript Object-Literals or JSON:
// evaluate the data expression
try {
eval("params.data = " + params.data);
} catch (e) {
params.data = {error: "server response failed with evaluation error: " + e.message
,data : params.data
}
}
//invoke the callback on the parent
try{
window.parent[ params.callback ](params.data || "no-data-returned");
}catch(e){
//if something went wrong - at least let's learn about it in the
// console (in addition to the timeout)
throw "Problem in passing POST response to host page: \n\n" + e.message;
}
</script>
</head><body></body></html>
It's not much automation and 'ready-made' library like jQuery and involes some 'manual' work - but it has the charm :)
If you're a keen fan of ready-made libraries - you can also check on Dojo Toolkit that when last I checked (about a year ago) - had their own implementation for the same mechanism.
http://dojotoolkit.org/
Good luck buddy, I hope it helps...
Is there a way to do a JSONP request using POST/PUT/DELETE?
No there isn't.
No. Consider what JSONP is: an injection of a new <script> tag in the document. The browser performs a GET request to pull the script pointed to by the src attribute. There's no way to specify any other HTTP verb when doing this.
Rather than banging our heads with JSONP method, that actually won't
support POST method by default, we can go for CORS .That will provide no big changes in the conventional way of programming. By simple Jquery Ajax call we can go with cross domains.
In CORS method, you have to add headers in server side scripting file, or in the server itself(in remote domain), for enabling this access. This is much reliable, since we can prevent/restrict the domains making unwanted calls.
It can be found in detail in wikipedia page.
I want to redirect after a successful ajax request (which I know how to do) but I want to pass along the returned data which will be used to load an iframe on the page I just redirected to.
What's the best way to pass such data along and use it to open and populate an iframe in the page I just redirected to?
EDIT:
I am passing a GET variable but am having to use the following to access it for use in my iframe src attribute:
function $_GET(q,s) {
s = (s) ? s : window.location.search;
var re = new RegExp('&'+q+'=([^&]*)','i');
return (s=s.replace(/^\?/,'&').match(re)) ? s=s[1] : s='';
}
var d = $_GET('thedata');
I assume there isn't really a more straightforward way to access the GET vars?
If it's not too much data, you could pass it as a get parameter in the redirect:
document.location = "/otherpage?somevar=" + urlescape(var)
Remember that urls are limited to 1024 chars, and that special chars must be escaped.
If it is beyond that limit your best move is to use server side sessions. You will use a database on the server to store the necessary information and pass a unique identifier in the url, or as a cookie on the users computer. When the new page loads, it can then pull the information out of the database using the identifier. Sessions are supported in virtually every web framework out of the box.
Another alternative may be to place the data as a hidden attribute in a form which uses the post method (to get around the 1024 char limit), and simulating a submission of the form in javascript to accomplish the redirect, including the data.