Users will be able to share images in my project. But let's say that user1 has already shared the image to user2, but user1 tries to share the picture again to user2. What would be the appropriate status code for "already shared"?
409 is the right status code. It means the item already exists.
In your case "image already shared"
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/409
I do not believe there a standard convention for this scenario. Status code 409 would highlight the fact the request was 1. Received and understood and 2. There was a server side conflict with processing and storing the data. Some other options would be 400, 403, and 422, but those could mean a variety of other issues with the request that could be misinterpreted.
Related
I have a HTML form, which I submit via http post.
There are two cases:
Case 1: The data is valid and data on the server will be updated accordingly
Case 2: The data is invalid and the http response contains an error message for the user.
Which http status codes should be used for each case?
I use htmx to submit the form. This means I don't need to use the POST/Redirect/GET pattern.
This question is not about JSON-APIs.
The complete list of HTTP response codes published by the Mozilla Foundation is pretty comprehensive and easy-to-read, so I'd recommend always consulting it as a guide. For the generic use-cases mentioned by you, there are a couple of different codes you can return - depending on what happens with the data on the server, and what you want to happen in the user's browser.
CASE 1: data is valid, data on server is updated
Base on your short description, the different status codes that might be applicable are:
200 (OK): you are updating an existing record on your own server - eg., the user is submitting a form which updates their existing contact information on your website - and information was received, and the record updated successfully. The response would usually contain a copy of the updated record.
201 (Created): you are not updating an existing record, but rather, creating a new record on your server - eg., your user is adding a new phone number to their contact details, which is saved in your database as a separate 'phone' record. The response should contain a copy of the newly created record.
205 (Reset Content): the same as 200, but implies that the browser view needs to be refreshed. This is useful when the record that is being updated has values that are dynamically calculated by the server, and which might change automatically depending on the values you're submitting. For example, if you have a user adding extra information to their online profile, which might grant them special status, badges and privileges on the website. This means, that if the user is viewing their profile information, that information will need to be updated with the new 'status' automatically granted by the server. The 205 response body will normally be empty, which means that to update the browser view your response-handling code will need to:
do further ajax requests and update the relevant part(s) of your
interface with new information from the server, or
redirect the user to a new URL, or
reload the entire page.
If working with HTMX, a 200 or 201 response would include the actual html snippet of the record that you want updated on the page - and HTMX will replace it automatically for you when it receives the response. With a 205 response, you could send an HX-Trigger response header that would call a custom event on the interface elements that need to update themselves - see the examples in the docs.
CASE 2: data is invalid, data on server is not updated
The status code that needs to be returned in case of an error varies depending on what caused the error. Errors that the server believes are the responsibility of the client - such as 'sending invalid data' - have a status code in the 4XX range. Some of the common errors in that range include 404 ('Not Found'), 403 ('Forbidden'), and 'Unauthorised' (401).
In the case of a client sending data that the server cannot process because it is 'not valid' - either because the request itself is malformed, or because the data doesn't pass some business validation logic - the current advice is to return status 400 (Bad Request).
Many years ago, some people believed that the status code 400 should only be used to indicate a malformed request (syntactical error) - not to indicate a failure in business validation logic (semantic error). There was a lot of debate, and temporarily a new status code (422) was created, that was supposed to cover semantic errors, exclusively. In 2014, however, the official definition of the status 400 code was changed to allow for the inclusion of both syntactical and semantical errors - which rendered status 422 essentially unnecessary.
You can find lots of discussions and explanations online about the differences between 400 and 422, and some people still argue passionately about this to this day. In practice, however, the 400 code is all you'll need - and you can include a response body in it that explains in detail, if needed, the cause of the error.
Note that when working with HTMX, a response with a 400 code should trigger an htmx:responseError event automatically. You can trap that event, for example, to update your form interface elements, in case of data validation errors caught by the server.
Well, 200 OK and 201 Created are the best for successful result.
For invalid data I would return 422 Unprocessable Entity, because the headers are correct, but body is not (though parseable by the server). The caveat is some HTTP clients won't handle 422 properly and in this case you have to use 400 Bad Request, however, the most of the modern clients will be fine.
You have said it is not about JSON APIs, but how will you meet this type of requirement - it is not clear whether this is relevant for your scenario???
SERVER DRIVEN BEHAVIOUR
I cannot see how a client could ever decide an HTTP status code based on input data. How would the client deal with these examples?
The call is not authenticated (cookie or token) - an API would return 401 - this tells the UI to perform a retry action.
The call is not authorized - an API would return 403 or 404 and the UI would present an error display.
The data is malformed or invalid according to domain specific checks - an API would return 400 and tell the UI what is wrong so that it can perform actions.
Something went wrong in server processing, eg data cannot be saved because database is down.
MY THOUGHTS
htmx looks interesting but a key requirement before using it would be ensuring that htmx can read server side error responses and use values returned. Maybe there is an elegant way to do this ...
Maybe I am just paranoid :). But it is worth being careful when choosing technologies that there are no blocking issues. Lack of error handlng control would be a blocking issue in most systems.
I'm using htmx 1.8 with asp.net core 6.0.
This works for me.
controller:
//server side validation failed
Response.StatusCode = 422;
return PartialView("Core", product);
client side javascript:
document.body.addEventListener('htmx:beforeOnLoad', function (evt) {
if (evt.detail.xhr.status === 422) {
//
// allow 422 responses to swap as we are using this as a signal that
// a form was submitted with bad data and want to rerender with the
// error messages
//
evt.detail.shouldSwap = true;
evt.detail.isError = false;
}
});
200 OK or 201 Created are the best choice for a successful POST request.
However, for invald data, you can pass 415 Unsupported Media Type
Where can I find a full list of (common) things that go wrong with an $.ajax() request, and what error types/codes they result in? On https://api.jquery.com/jQuery.ajax/#jqXHR I can see all the possible outcomes, but not what can cause such an outcome. For example, I wonder
It says about .error() Possible values for the second argument (besides null) are "timeout", "error", "abort", and "parsererror". but what events would result in the second argument being null?
What does it mean if the jqXHR object has status is 0 (which I've seen happens sometimes, but I have no clue when or how or why)?
Reversely, if I were to think "what would happen to incoming requests if I reboot my server now" or "what would happen if the user's network connection was flakey", how can I know which error type / jqXHR status / responseText message etc. that would cause for the user?
Possibly this question has the very simple answer that "null textStatus", "0 jqXHR status" and "client side network connection issue" are all the same thing (as in you either have all three or none), or something close to that, but I can't find this documented anywhere.
There is called "complete" callback, check what status it returns. what i know is the server should return these status as such, but what you have is an exception. Adding timeout might help as well.
I know someone who is writing an API, and wants to use HTTP status codes to report the outcome of queries. e.g. if the user calls example.com/api/product_info?product_id=X, and the product doesn't exist, it would return HTTP status 400: Bad Request. I think that, since this is a valid call (i.e. the actual HTTP request is not malformed), it should return a 200 code response, and just have the body of the response something like {status: 'error'; message: 'No such product'}.
So my question is,
1) Is it appropriate to use HTTP status codes to convey non-HTTP program state, as in the example above?
2) Is there some standard, or at least widely used, specification describing when HTTP status codes are appropriate for use?
I was actually just talking about this the other day - http://blogs.mulesoft.org/api-best-practices-response-handling/
Your status code should reflect the response of the API, as 200 is "OK" and should be used for data that is successfully returned. However, 201 should be used for created items.
As mentioned already, in the event where the user tries a call but it fails (ie: users/?id=5) the server could return back a 400 to inform the user that it was a Bad Request, or a 404 if the resource doesn't exist.
It also depends on the action - if they are searching for a user and there are no responses, I wouldn't return an error, just a 200 with no results found. However, if they are trying to do a PUT or PATCH on a user that doesn't exist I would tell them with an error- as chances are there's a problem within their application somewhere.
In the link posted above you'll find more status codes, but one of the biggest advantages to using status codes is that it informs the client just though the header what actually happened with the server. This allows them to do a relatively quick (and low memory) check instead of having to deserialize the body and loop through an array looking for an errors key.
Essentially, you're giving them the tools to quickly and easily understand what is happening- something that I think every (sane) developer appreciates.
Hope this helps!
- Mike
i am working on status update and commenting application in asp.net mvc3 like Facebook wall and comment. User can comment my wall and all stuff like Facebook.
http://demos.99points.info/facebook_wallpost_system/
like above demo, i want to create my application.
how can i do that using mvc3 and ajax?
i successfully updated user status to database but cant get all status updates of same user, i want to use partial view to display all status of user below the status textarea.
and if user write some status and share status that time status message saved in database and again reflect to same view Asynchronously.
how can i do that using ajax?
I'm going to answer this in broad terms as I don't have any knowledge of asp.net or mvc3. However, it seems to me that you're looking for more architectural direction.
You will need to setup an endpoint which generates the status page, call it /status.asp. This will create the text area and load the existing status messages from your database.
Then create a second endpoint, say /api/status.asp. This is not a view, but an API in your application that let's a user create (and, if you want, retrieve/modify/delete?) a status.
When a user hits enter in the textarea, fire off an XHR request to /api/status.asp with the new status. It is common, but not required, to do this as a POST request (read up on REST - http://en.wikipedia.org/wiki/Representational_State_Transfer). This API should then save the new status to your DB, and return the uid of the status along with the status message, perhaps as JSON (or XML or YAML if you prefer, it's up to you). For example, in JSON:
{
status: [
{
uid: '1234567890987654321'
msg: 'Hello World'
}
]
}
(To send the XHR request it's easiest to use a JS library like Dojo ( http://dojotoolkit.org/reference-guide/dojo/xhr.html#dojo-xhr ) or JQuery ( http://api.jquery.com/jQuery.ajax/ ).)
When your XHR request returns, check the status is a 200 (everything went OK), then read the data returned. Write some Javascript to create a new DOM node, inject the status message into that DOM node and add it to the bottom of the previous status nodes.
Bonus Points:
If you want person B to be looking at person A's /status.asp page and for that page to auto-update when person A posts a new status, you'll need to do a little more work. Firstly, modify /api/status.asp to return a list of the last x (say, 10?) status updates when called via HTTP GET. Include the UID of each status along with the status text.
Call your /api/status.asp API repeatedly* (perhaps with a timestamp of the last time you called it, and get your API to only return status posts after that time), loop over the the results and check to see if that post is already included in the users page (perhaps by having an id on each DOM node matching the UID of the status). If not, add it to the page.
*you have a number of options for doing this. For example, simply setup a JS timeout (easy, but not very efficient), or use Comet (eg http://cometd.org/) or WebSockets ( http://websocket.org/ ). I'd go for a timeout first, get it working and then figure out if a better technology is required.
It appears that when you make an XMLHttpRequest from a script in a browser, if the browser is set to work offline or if the network cable is pulled out, the request completes with an error and with status = 0. 0 is not listed among permissible HTTP status codes.
What does a status code of 0 mean? Does it mean the same thing across all browsers, and for all HTTP client utilities? Is it part of the HTTP spec or is it part of some other protocol spec? It seems to mean that the HTTP request could not be made at all, perhaps because the server address could not be resolved.
What error message is appropriate to show the user? "Either you are not connected to the internet, or the website is encountering problems, or there might be a typing error in the address"?
I should add to this that I see the behavior in FireFox when set to "Work Offline", but not in Microsoft Internet Explorer when set to "Work Offline". In IE, the user gets a dialog giving the option to go online. FireFox does not notify the user before returning the error.
I am asking this in response to a request to "show a better error message". What Internet Explorer does is good. It tells the user what is causing the problem and gives them the option to fix it. In order to give an equivalent UX with FireFox I need to infer the cause of the problem and inform the user. So what in total can I infer from Status 0? Does it have a universal meaning or does it tell me nothing?
Short Answer
It's not a HTTP response code, but it is documented by WhatWG as a valid value for the status attribute of an XMLHttpRequest or a Fetch response.
Broadly speaking, it is a default value used when there is no real HTTP status code to report and/or an error occurred sending the request or receiving the response. Possible scenarios where this is the case include, but are not limited to:
The request hasn't yet been sent, or was aborted.
The browser is still waiting to receive the response status and headers.
The connection dropped during the request.
The request timed out.
The request encountered an infinite redirect loop.
The browser knows the response status, but you're not allowed to access it due to security restrictions related to the Same-origin Policy.
Long Answer
First, to reiterate: 0 is not a HTTP status code. There's a complete list of them in RFC 7231 Section 6.1, that doesn't include 0, and the intro to section 6 states clearly that
The status-code element is a three-digit integer code
which 0 is not.
However, 0 as a value of the .status attribute of an XMLHttpRequest object is documented, although it's a little tricky to track down all the relevant details. We begin at https://xhr.spec.whatwg.org/#the-status-attribute, documenting the .status attribute, which simply states:
The status attribute must return the response’s status.
That may sound vacuous and tautological, but in reality there is information here! Remember that this documentation is talking here about the .response attribute of an XMLHttpRequest, not a response, so this tells us that the definition of the status on an XHR object is deferred to the definition of a response's status in the Fetch spec.
But what response object? What if we haven't actually received a response yet? The inline link on the word "response" takes us to https://xhr.spec.whatwg.org/#response, which explains:
An XMLHttpRequest has an associated response. Unless stated otherwise it is a network error.
So the response whose status we're getting is by default a network error. And by searching for everywhere the phrase "set response to" is used in the XHR spec, we can see that it's set in five places:
To a network error, when:
the open() method is called, or
the response's body's stream is errored (see the algorithm described in the docs for the send() method)
the timed out flag is set, causing the request error steps to run
the abort() method is called, causing the request error steps to run
To the response produced by sending the request using Fetch, by way of either the Fetch process response task (if the XHR request is asychronous) or the Fetch process response end-of-body task (if the XHR request is synchronous).
Looking in the Fetch standard, we can see that:
A network error is a response whose status is always 0
so we can immediately tell that we'll see a status of 0 on an XHR object in any of the cases where the XHR spec says the response should be set to a network error. (Interestingly, this includes the case where the body's stream gets "errored", which the Fetch spec tells us can happen during parsing the body after having received the status - so in theory I suppose it is possible for an XHR object to have its status set to 200, then encounter an out-of-memory error or something while receiving the body and so change its status back to 0.)
We also note in the Fetch standard that a couple of other response types exist whose status is defined to be 0, whose existence relates to cross-origin requests and the same-origin policy:
An opaque filtered response is a filtered response whose ... status is 0...
An opaque-redirect filtered response is a filtered response whose ... status is 0...
(various other details about these two response types omitted).
But beyond these, there are also many cases where the Fetch algorithm (rather than the XHR spec, which we've already looked at) calls for the browser to return a network error! Indeed, the phrase "return a network error" appears 40 times in the Fetch standard. I will not try to list all 40 here, but I note that they include:
The case where the request's scheme is unrecognised (e.g. trying to send a request to madeupscheme://foobar.com)
The wonderfully vague instruction "When in doubt, return a network error." in the algorithms for handling ftp:// and file:// URLs
Infinite redirects: "If request’s redirect count is twenty, return a network error."
A bunch of CORS-related issues, such as "If httpRequest’s response tainting is not "cors" and the cross-origin resource policy check with request and response returns blocked, then return a network error."
Connection failures: "If connection is failure, return a network error."
In other words: whenever something goes wrong other than getting a real HTTP error status code like a 500 or 400 from the server, you end up with a status attribute of 0 on your XHR object or Fetch response object in the browser. The number of possible specific causes enumerated in spec is vast.
Finally: if you're interested in the history of the spec for some reason, note that this answer was completely rewritten in 2020, and that you may be interested in the previous revision of this answer, which parsed essentially the same conclusions out of the older (and much simpler) W3 spec for XHR, before these were replaced by the more modern and more complicated WhatWG specs this answers refers to.
status 0 appear when an ajax call was cancelled before getting the response by refreshing the page or requesting a URL that is unreachable.
this status is not documented but exist over ajax and makeRequest call's from gadget.io.
Know it's an old post. But these issues still exist.
Here are some of my findings on the subject, grossly explained.
"Status" 0 means one of 3 things, as per the XMLHttpRequest spec:
dns name resolution failed (that's for instance when network plug is pulled out)
server did not answer (a.k.a. unreachable or unresponding)
request was aborted because of a CORS issue (abortion is performed by the user-agent and follows a failing OPTIONS pre-flight).
If you want to go further, dive deep into the inners of XMLHttpRequest. I suggest reading the ready-state update sequence ([0,1,2,3,4] is the normal sequence, [0,1,4] corresponds to status 0, [0,1,2,4] means no content sent which may be an error or not). You may also want to attach listeners to the xhr (onreadystatechange, onabort, onerror, ontimeout) to figure out details.
From the spec (XHR Living spec):
const unsigned short UNSENT = 0;
const unsigned short OPENED = 1;
const unsigned short HEADERS_RECEIVED = 2;
const unsigned short LOADING = 3;
const unsigned short DONE = 4;
from documentation http://www.w3.org/TR/XMLHttpRequest/#the-status-attribute
means a request was cancelled before going anywhere
Since iOS 9, you need to add "App Transport Security Settings" to your info.plist file and allow "Allow Arbitrary Loads" before making request to non-secure HTTP web service. I had this issue in one of my app.
Yes, some how the ajax call aborted. The cause may be following.
Before completion of ajax request, user navigated to other page.
Ajax request have timeout.
Server is not able to return any response.