So I've read that you cannot expect a default order when requesting json. I've seen this in action making a call to a little api that I built, that will return a jumbled, random order of elements each time I make a different call.
How does a site like ticketfly's api ( call it here http://www.ticketfly.com/api/events/upcoming.json?venueId=57 ) always ensure that the json returned is in a specific order?
The event ids always first, etc.
Thanks for shedding some light on the situation.
If you are in control of the endpoint API then you can hardcode the order in which you render the properties. Though I have to ask why exactly do you need the JSON properties in a particular order? You will finally be accessing the properties via there property names so the order in which they appear in the JSON should not ideally matter.
EDIT : Since your bosses insist on this (what can one say now?):
You can try and see if any of the following suits your needs:
Try hardcoding the display order in the view's representation. This means you will need to echo/print each property name explicitly in the view script. In PHP it could be something like echo $variable_representing_json["id"]; and so forth. Note that with this approach you needn't change the original JSON representation.
If you want the original JSON representation to be changed then depending on how you are doing the process it varies in difficulty:
If it's string concatenation that you are using to represent the json then hard-code the order in which the json properties get concatenated in the string.
In some languages the display order of properties is actually a representation of the order in which the properties were defined. In simple words if $var is an empty json representation then you should define $var["id"] = {some_val} first to display it first.
If you are using a framework for processing the JSON data it may have its own quirks irrespective of how you define your representation. In such cases you will have to try and see if you can work around the issue or if it gives any helper methods.
Related
We receive a JSON object from network along with a hash value of the object. In order to verify the hash we need to turn that JSON into a string and then make a hash out of it while preserving the order of the elements in the way they are in the JSON.
Say we have:
[
{"site1":
{"url":"https://this.is.site.com/",
"logoutURL":"",
"loadStart":[],
"loadStop":[{"someMore":"smthelse"}],
"there's_more": ... }
},
{"site2":
....
}
]
The Android app is able to get same hash value, and while debugging it we fed same simple string into both algorithms and were able to get out same hash out of it.
The difference that is there happens because of the fact that dictionaries are unordered structure.
While debugging we see that just before feeding a string into a hash algorithm, the string looks like the original JSON, just without the indentations, which means it preserves the order of items in it (on Android that is):
[{"site1":{"url":"https://this.is.site.com/", ...
While doing this with many approaches by now I'm not able to achieve the same: string that I get is different in order and therefore results in a different hash. Is there a way to achieve this?
UPDATE
It appears the problem is slightly different - thanks to #Rob Napier's answer below: I need a hash of only a part of incoming string (that has JSON in it), which means for getting that part I need to first parse it into JSON or struct, and after that - while getting the string value of it - the order of items is lost.
Using JSONSerialization and JSONDecoder (which uses JSONSerialization), it's not possible to reproduce the input data. But this isn't needed. What you're receiving is a string in the first place (as an NSData). Just don't get rid of it. You can parse the data into JSON without throwing away the data.
It is possible to create JSON parsers from scratch in Swift that maintain round-trip support (I have a sketch of such a thing at RNJSON). JSON isn't really that hard to parse. But what you're describing is a hash of "the thing you received." Not a hash of "the re-serialized JSON."
I know that I can access the JSON data like so http://base-template.squarespace.com/news/?format=json-pretty. But what I want to access lets says a property on that like news.items? http://base-template.squarespace.com/news/items/?format=json-pretty throw an error. Is there a way to drill into the JSON data via the URL?
Yes, you can access a collection's items using the same format=json-pretty query parameter as you mentioned.
Do note, however, that:
The URL must exist (which in your second 'news' example is not the case)
To get a list of items from a collection, you use the format=json-pretty on the collection, the scope into items from there.
When performing this type of request via Javascript, you'll probably want to simply use format=json since the 'pretty' line breaks and indenting aren't necessary in that case.
For example, using the base-template as you have already mentioned, to get the blog items you would use: https://base-template.squarespace.com/blog?format=json-pretty. Within the JSON, you'll see an 'items' array, which is the data you're looking for (See the image below for a screenshot of this.). If that website had a "/news" collection, you could do similar.
Similarly, if you wanted to view the JSON output from a specific item, you would, for example, use: https://base-template.squarespace.com/blog/2016/7/15/most-recent-sample-blog-post?format=json-pretty
I want to use query string as json, for example: /api/uri?{"key":"value"}, instead of /api/uri?key=value. Advantages, from my point of view, are:
json keep types of parameters, such are booleans, ints, floats and strings. Standard query string treats all parameters as strings.
json has less symbols for deep nested structures, For example, ?{"a":{"b":{"c":[1,2,3]}}} vs ?a[b][c][]=1&a[b][c][]=2&a[b][c][]=3
Easier to build on client side
What disadvantages could be in that case of json usage?
It looks good if it's
/api/uri?{"key":"value"}
as stated in your example, but since it's part of the URL then it gets encoded to:
/api/uri?%3F%7B%22key%22%3A%22value%22%7D
or something similar which makes /api/uri?key=value simpler than the encoded one; in this case both for debugging outbound calls (ie you want to check the actual request via wireshark etc). Also notice that it takes up more characters when encoded to valid url (see browser limitation).
For the case of 'lesser symbols for nested structures', It might be more appropriate to create a new resource for your sub resource where you will handle the filtering through your query parameters;
api/a?{"b":1,}
to
api/b?bfield1=1
api/a?aBfield1=1 // or something similar
Lastly for the 'easier to build in client side', i think it depends on what you use to create your client, usually query params are represented as maps so it is still simple.
Also if you need a collection for a single param then:
/uri/resource?param1=value1,value2,value3
Should I treat all api response as "resource" and return a JSON object or simple array would be appropriate as well ?
for instance are all of the below responses valid?
GET /rest/someresource should return collection of ids
[{id:1},{id:2}]
{{id:1},{id:2}}
[1,2]
GET /rest/someresource?id>0 search for ids bigger than zero and return collection of ids
[{id:1},{id:2}]
{{id:1},{id:2}}
[1,2]
Collection Resources
It is acceptable to return an array of resources - either a list of ids, or object structures - such a thing is commonly known as a 'collection' resource.
See http://51elliot.blogspot.com.au/2014/06/rest-api-best-practices-4-collections.html for an examination of resources and collections.
While not required by REST, it's common to use a plural noun to refer to a collection resource - e.g.
/rest/someresources
REST also requires the use of defined media types, and there are a couple available to assist with collections, e.g.:
Collection+json
Provides a structure with meta data around a list of items wherein you define the structure of each item as your resource
HAL
provides a structure with embedded collections and embedded resources
And many more
All provide a defined structure for including hypermedia links for your resource, or each resource in your collection - and if you are doing REST this is one of the things that the spec says you MUST do (even though many people don't).
Your Proposed Json Structures
Some more specific comments on your proposed json structures:
Option 2 is not valid json. Consider:
{{id:1},{id:2}}
A json object must have a name:value pair, e.g.
{somename:{id:1},someothername:{id:2}}
would be valid - but not very useful!
Also - strictly for json, the name should be enclosed in quotes. the value may be enclosed in quotes if it is a string.
So if you don't want to use a commonly used media type as referenced above, your options are 1 or 3. which should be:
[{"id":1},{"id":2}]
[1, 2]
Both are valid, however option 1 will give you more flexibility to add more properties to each element of the array if you decide in the future you would like to return more than an id. e.g. at some point in the future you might decide to return:
[{"id":1,"name":"fred"},{"id":2,"name":"wilma"}]
Option 3 will only ever be able to return a list of ids.
So personally I would go with option 1.
Depends on how RESTful you're aiming to be.
In addition to what #Chris Simon said, I'll add that if the server would only return IDs at GET /rest/someresource, the client would have to repeatedly call something like GET /rest/someresource/{id} in order to obtain data (it can display on the UI), right? This in turn would just increase the load on the server. If the id would be enough, you can probably get away with the proposed solution.
Also, once you decide you'd better be consistent.
Given that the 2nd option is not even valid, and the last is pretty limiting, I'd also go for the first option, JSON.
Just to make it clear we are talking about different representations of the same resource here:
By GET /rest/someresource both [{id:1},{id:2}] and [1,2] are valid responses, but you should make clear which one you want to see, e.g. with the prefer header. So by Prefer: return=minimal you would return [1,2] and if the header is not present, then [{id:1},{id:2}]. Just make sure that the prefer header is registered by the vary header, or you will have caching troubles.
By GET /rest/someresource?id>0 you filter your collection. So either the /rest/someresource?id>0 URI identifies a different filtered collection resource or it identifies the same collection resource, but with the filter query string your client indicates that it is waiting for a filtered representation of the resource and not the full representation. You can use the same by the minimal representation if you don't want to use the prefer header: GET /rest/someresource?return=minimal.
Note that if you want your client to query again, then you should send them hyperlinks in your response. The REST client must get the URIs (or URI templates) from these hyperlinks and it should not start to build URIs on its own.
I got an anonymous array which I want to deserialize, here the example of the first array object
[
{ "time":"08:55:54",
"date":"2016-05-27",
"timestamp":1464332154807,
"level":3,
"message":"registerResourcePath ('', '/sap/bc/ui5_ui5/ui2/ushell/resources/')",
"details":"","component":"sap.ui.ModuleSystem"},
{"time":"08:55:54","date":"2016-05-27","timestamp":1464332154808,"level":3,"message":"URL prefixes set to:","details":"","component":"sap.ui.ModuleSystem"},
{"time":"08:55:54","date":"2016-05-27","timestamp":1464332154808,"level":3,"message":" (default) : /sap/bc/ui5_ui5/ui2/ushell/resources/","details":"","component":"sap.ui.ModuleSystem"}
]
I tried deserializing using CL_TREX_JSON_SERIALIZER, but it is corrupt and does not work with my JSON, here is why
Then I tried /UI2/CL_JSON, but it needs a "structure" that perfectly fits the object given by the JSON Object. "Structure" means in my case an internal table of objects with the attributes time, date, timestamp, level, messageanddetails. And there was the problem: it does not properly handle references and uses class description to describe the field assigned to the field-symbol. Since I can not have a list of objects but only a list of references to objects that solution also doesn't works.
As a third attempt I tried with the CALL TRANSFORMATION as described by Horst Keller, but with this method I was not able to read in an anonymous array, and here is why
My major points:
I do not want to change the JSON, since that is what I get from sap.ui.log
I prefere to use built-in functionality and not a thirdparty framework
Your problem comes out not from the anonymity of array, but from the awkwardness of SAP JSON (De)serializer, which doesn't respect double quotes, which enclose JSON attributes. The issue is thoroughly described in this answer.
If you don't want to change your JSON on-the-fly, the only way you have is to change CL_TREX_JSON_DESERIALIZER class like this.
/UI5/CL_JSON_PARSER parses JSONs with unknown format.
Note that it's got "for internal use" written on it so many times that you probably should take it seriously and clone its code to fixate it.