What should be the standard format for returning success JSON, failure JSON and error JSON? I visited many so called RESTful APIs but almost all have their own way to return success, failure and error JSON? Is there any recommended JSON format that should be followed/referenced?
Thanks
Good question. REST does set some conventions, but unlike for GET or PUT HTML where there is at least a convention for the tag names to be sent, there is little about the vocabulary to be used for JSON... I believe any truly useful long-term usage will need to develop formal vocabularies beyond basic transaction behaviors, whether HTML, XMPP, or a dialect of JSON (e.g., in XMPP, unlike say WebSockets alone, you can develop clients which know how to handle subscription and publishing for any Pubsub server).
To signal Success, errors or any other status you should use standard http status codes.
You can also in case of an error return a json containing something like code, severity and message.
You should follow the HTTP Status Codes as per its description. It will be good to have all your REST failure/error responses to have some common fields like errorCode and errorMessage that describes the status you are sending back.
{
"apiStatus":{
"errorCode":"validation.error.invalidId",
"errorMessage":"The Id entered is not valid"
}
"yourContentIfany": ....
}
Related
What are the good choice for API error code response pattern?
Instead of using different codes indicating different type of error
100001 // username not provided
100002 // password not provided
100003 // password too short
...
I see some other use patterns like the following (non-sequential) ...
20000
20001
20004
20015
Are there any other recommendations?
In my experience developing and using web services, I have found that a strategy of using a combination of top-level HTTP status codes and lower level API error codes work reasonably well. Note that the lower level API error codes don't need to be integers, but can be any enumeration. For a well-known public example, AWS Simple Email Service (SES) uses this strategy of using both HTTP status codes and API level error codes. You can see a sample error code response for SES here. Note that although SES uses XML response error payloads, this strategy works equally well for JSON response payloads.
In my experience, there are a few things that you need to keep in mind when using this strategy:
Strive to return the correct HTTP response code: HTTP is a ubiquitous protocol and is no doubt understood by your web container. Its response codes fit naturally into REST web services. As such, leverage it! If your web service encounters an error condition, you should do your best to return the correct HTTP status code in whose context, the API error code has meaning. One my biggest headaches in debugging issues with web services occur when developers just unconditionally throw arbitrary (usually runtime) exceptions back up the stack. The result is that everything gets returned back to the caller as an HTTP 500 (Internal Server Error) status code even when that's not the case (e.g. the client sends garbage data and the server just can't process it. Some common HTTP status codes you might want to design for include:
400 Bad Request: There is an issue with the client's request. Note this error isn't just used for things like broken JSON syntax in a POST request, but it is also a legitimate response code for semantic issues as well (i.e. the JSON request payload conformed to the prescribed schema, but there was an issue with the data in the payload, such as a number being negative when it is supposed to be only positive).
401 Unauthorized: The caller's credentials were invalid (i.e. authorization error).
403 Forbidden: The caller's credentials were valid, but their access level isn't sufficient to access the resource (i.e. authentication error).
404 Not Found: The resource of the URL doesn't exist.
500 Internal Server Error: Something bad happened inside the server itself, this error could be anything.
502 Bad Gateway: An error occurred when calling downstream service.
503 Service Unavailable: A useful response code for when you get hammered with a ton of "happy" customers who are inadvertently DDOS'ing your service.
504 Gateway Timeout: Like the 502 status code, but indicates a timeout instead of an actual error with the downstream service, per se.
HTTP response codes are the top-level codes, and API error codes only have meaning within that context: By this, I mean that your API error codes are only meaningful for certain HTTP response codes. For example, in the table of SES error codes, each error code is only tied to a single HTTP(S) response code. The error codes ConfigurationSetDoesNotExist and InvalidParameterValue only make sense when a 400 Bad Request is returned by SES - it wouldn't make sense to return these status codes when a 500 Internal Server Error is returned. Similarly, if you were writing a web service that called downstream services and databases, you might have a FooDownstreamServiceTimedOut error code that you would return with a 504 Gateway Timeout HTTP status code when a downstream web service call timed out to the "Foo" web service. You might also have a MyDatabaseError error code that you would return with a 500 Internal Server Error HTTP status code when your query to the internal DB fails.
Have a uniform error code schema irrespective of status codes: Your clients need to be able to process your error content programmatically. As such, it needs to conform to a certain schema. Ideally, your API error code schema should include the error code (i.e. name or ID, etc.). You also probably want to include a natural language description of the error code and the ID/GUID of the request that you are responding to. For an example of an error schema, see this sample AWS SES response and schema. Additionally, you might also want to consider returning a client ID in the response. This is as much for your own benefit as the client's since it can help you drill down into the data to see if one particular client is getting a glut of particular errors vs. your other clients.
Consider returning natural language descriptions of the error codes in the response: To make things easier on your clients, you might want to consider not just returning the error code in the error payload, but a natural language description as well. This kind of behavior can immediately help confused and busy engineers who really don't care that much about your service quickly diagnose what's happening so that they can resolve the issue ASAP. btw, enabling engineers to quickly diagnose issues with your service increases the all-important "uptime" metric that your customers and managers will no doubt care about.
Don't feel obliged to use integers, use enumerations instead: The notion of "error codes" conjures up images of outdated technologies and codebooks where you had to look up what an error meant. It arose from the programming dark ages when engineers needed to fit all possible errors into a byte of space, or a nibble or whatever. Those days are gone, and your error code can be a string, likely without any meaningful impact on performance. You might as well take advantage and make the error code meaningful, as a means of keeping things simple.
Return info to clients that they might need to debug, but be mindful of security: If possible, return whatever debug info your clients may need. However, if your service potentially deals with sensitive information such as credit card numbers and the like, you probably don't want to pass that info around for obvious reasons.
Hope that helps.
A recommendation by the IETF (internet standards body) is using the application/problem+json mediatype.
Notable is that they don't use random numbers, they use strings (specifically uris) to identify errors.
This is a subjective question, but even if you don't use their format, I'd argue that username-not-provided is better in almost every way to 100001.
I would say this heavily depends on what kind of API you're providing.
I were to always include a field called ack or something similar in every response that has three states: failure, warning, success. Success obviously being everything went well. On warning, the request went through and the JSON will contain the expected output, but it will also include a warning string, or even better in case multiple warnings could occur an array called errors which consists of multiple objects containg code, string and type. This array will also be returned in case of failure, and nothing else but this array.
The array contains one object per error or warning, having a code (I would suggest going with your initial idea of 10001, 10002, ...) and a string explaining the error in a very short phrase (e.g. Username contains invalid characters). The type is either error or warning, which is useful in case of a failure ack that contains not only errors but also warnings.
This makes it easy to look up errors by their code (I would provide a page, also with an API, that contains all the error codes in a table along with their short and long description plus common causes/fixes/etc. - All this information should also be available via an API where they can be accessed by providing the error code) while still having a quick short text response so the user can tell what's wrong in most cases without having to look up the error.
This also allows for easy output of warnings and errors to the end user, not just the developers. Using my idea with the API call to get informations about an error, developers using your API could easily provide full information about errors to end-users when needed (including causes/fixes/whatever you see fit).
Instead of writing your own API standard from scratch adopt one of the already available, for example the JSON API standard:
If you’ve ever argued with your team about the way your JSON responses should be formatted, JSON API can be your anti-bikeshedding tool.
By following shared conventions, you can increase productivity, take advantage of generalized tooling, and focus on what matters: your application.
Clients built around JSON API are able to take advantage of its features around efficiently caching responses, sometimes eliminating network requests entirely.
If you decide to go with JSON API it has a section dedicated to errors and a few error examples.
For many years, many developent companies have created things like bitmask for errors, so they can encode multiple variables inside the error:
000 - all ok
001 - something failed with X
010 - something failed with Y
011 - something failed with X and Y
100 - something failed with Z
101 - something failed with X and Z
The limitation is that that limits the error space into however many bytes you decide on the encoding, like 16 or 32 possible combinations, it may be enough for you, or not.
You see this being common in COM+
https://learn.microsoft.com/en-us/windows/desktop/com/com-error-codes-1
I hope this helps.
I stumbled over a practice that I found to be quite widespread. I even found a web page that gave this a name, but I forgot the name and am not able to find that page on google anymore.
The practice is that every JSON response from a REST service should have the following structure:
{
"status": "ok",
"data": { ... }
}
or in an error case:
{
"status": "error",
"message": "Something went wrong"
}
My question: What is the point why such a "status" property should be required in the JSON? In my opinion that is what HTTP status codes were made for.
REST uses the HTTP means of communication between client and server, for example the "DELETE" verb should be used for deleting. In the same way, 404 should be used if a resource is not found, etc. So inline with that thinking, any error cases should be encoded properly in the HTTP status.
Are there specific reasons to return a HTTP 200 status code in an error case and have the error in the JSON instead? It just seems to make the javascript conditional branches more complex when processing the response.
I found some cases where status could be "redirect" to tell the application to redirect to a certain URL. But if the proper HTTP status code was used, the browser would perform the redirection "for free", maintaining the browsing history properly.
I picture mainly two possible answers from you:
Either there are two quarreling communities with their favorite approach each (use HTTP status always vs. use HTTP status never)
or I am missing an important point and you'll tell me that although the HTTP status should be used for some cases, there are specific cases where a HTTP status does not fit and the "status" JSON property comes into play.
You are right. I think what you are seeing is a side-effect of people not doing REST correctly. Or just not doing REST at all. Using REST is not a pre-requisite for a well-designed application; there is no rule that webapps have to be REST-ful.
On the other hand, for the error condition, sometimes apps want to return a 200 code but an error to represent a business logic failure. The HTTP error codes don't always match the semantics of application business errors.
You are mixing two different Layers here:
HTTP is for establishing (high-level) connections and transferring data. The HTTP status codes thus informs you if and how the connection was established or why it was not. On a successful connection the body of the HTTP request could then contain anything (e.g. XML, JSON, etc.), thus these status code have to define a general meaning. It does not inform you about the correctness or type (e.g. error message or data) of the response.
When using JSON for interchanging data you could certainly omit the status property, however it is easier for you to parse the JSON, if you know if it includes the object you were requesting or an error message by just reading one property.
So, yes, it is perfectly normal to return a 200 status code and have a "status": "error" property in your JSON.
HTTP status codes can be caused by a lot of things, including load balancers, proxies, caches, firewalls, etc. None of these are going to modify your JSON output, unless they completely break it, which can also be treated as an error.
Bottom line: it's more reliable to do it via JSON.
What is the best practice with regard to sending error responses in a JSON web service? I have seen it done several ways and wanted to know whether there were any agreed-upon standards or best practices among the choices.
I've seen it done where the response includes indication of success or failure as well as the data to be returned or a suitable error message, e.g.
[{'success':true, 'data':{...}]
[{'success':false, 'data':{'message':'error'}]
But I've also seen examples where the JSON object only includes data, and the service uses the normal HTTP error codes to indicate a problem (403, 404, 500, etc). (This is how the Twitter API does it.)
Is there a "right" way to do this, or is it just a matter of style? Is the latter method more "RESTful?"
In a "RESTful" approach, the primary error response is indicated by an appropriate status code (4xx/5xx).
Your message should provide addtional, application-specific hints on how to recover from the error. This may include human-readable representations of the error that has occured or some kind of more technical indicator (i.e. providing an Exception class name).
For being generic, keep to a fix syntax for your error messages. This allows you to introduce new error messages withour breaking the clients.
Use the appropriate HTTP codes and put what you now call "data" as the body of the response. This is the only correcty RESTful way to make the API users aware of an error.
Just doing this will not make your API RESTful, but not doing it will surely make your API non RESTful.
An example of well-used HTTP status codes for errors is in the Dropbox v1 API reference, have a look at the "Errors" sections under each method, they explain which error codes you should expect and what is the associated meaning in that particular method.
G'day gurus,
I'm calling the REST APIs of an enterprise application that shall remain nameless, and they return JSON such as the following:
throw 'allowIllegalResourceCall is false.';
{
"data": ... loads of valid JSON stuff here ...
}
Is this actually valid JSON? If (as I suspect) it isn't, is there any compelling reason for these kinds of shenanigans?
The response I received from the application vendor is that this is done for security purposes, but I'm struggling to understand how this improves security much, if at all.
Thanks in advance!
Peter
According to
http://jsonlint.com/
It is not.
Something like the below is.
{
"data": "test"
}
Are they expecting you to pull the JSon load out of the message above?
Its not a JSON format at all. From your question it seems you are working with enterprise systems like JIVE :). I am also facing same issue with JIVE api. This is the problem with their V3 API. Not standard , but following thing worked for me. (I am not sure if you are talking about JIVE or not)
//invalid jason response... https://developers.jivesoftware.com/community/thread/2153
jiveResponse = jiveResponse.Replace
("throw 'allowIllegalResourceCall is false.';",String.Empty);
There is a valid reason for this: it protects against CSRF attacks. If you include a JSON url as the target of a <script> tag, then the same-origin policy doesn't apply. This means that a malicious site can include the URL of a JSON API, and any authenticated users will successfully request that data.
By appropriately overriding Object.prototype and/or Array.prototype, the malicious site can get any data parsed as an object literal or array literal (and all valid JSON is also valid javascript). The throw statement protects against this by making it impossible to parse javascript included on a page via <script> tags.
Definitely NOT valid JSON. Maybe there's an error in the implementation that is mixing some kind of debug output with the correct output?
And, by no means this is for security reasons. Seems to me this is a plain bug.
throw 'allowIllegalResourceCall is false.'; is certainly not valid JSON.
What MIME type is reported?
It seems they have added that line to prevent JSON Hijacking. Something like that line is required to prevent JSON Hijacking only if you return a JSON array. But they may have added that line above all of their JSON responses for easier implementation.
Before using it, you have to strip out the first line, and then parse the remaining as JSON.
We are in the middle of a ongoing discussion about how to handle REST exceptions.
Response Content type : JSON
Two solutions we have:
Throw all the unchecked exceptions as a JSON response.
Send Request Invalid Response code.
Arguments:
When its a error, why return JSON? Just send a invalid response code.
Counter Argument:
Response code are too technical to handle for normal developers.
Whats your say??
For a JSON API I recently developed I do both. I always respond with valid JSON (well, assuming I respond at all). If I detect an invalid request, I use status 400. If I detect a server error (which I don't believe is caused by an invalid request), I use a 5xx status. The JSON object contains a special key that is only set for errors, with a string value.
I think this is a good solution that respects REST principles, and can be used in multiple ways. The same solution is used by some other JSON APIs, such as Yahoo Search. Try http://search.yahooapis.com/ImageSearchService/V1/imageSearch?appid=YahooDemo&output=json .
Use error codes like for HTTP. So 50* for any exception cause by some internal problem. And 40* for bad arguments. Avoid using your own defined codes as far as its possible. The idea is to have a "uniform" interface.
In general.
204 for success without sending any content
200 for success with a json representation of the resource
And if its not a successful operation return appropriate response code. You can choose to optionally return a json. To simplify things you can have a common format (json) for all error responses.
http://en.wikipedia.org/wiki/REST is a must read before you freeze on your api specs.