I am building a REST API which creates a resource. The resource has only one attribute which is a rather long and unique string. I am planning to send this data to the API as JSON. I see two choices for modeling the data as JSON
A primitive JSON String data type
A JSON object with one String attribute.
Both the options work.
Which of these two options is preferred for this context? And why?
Basic Answer for Returning
I would personally use option 2, which is: `A JSON object with one String attribute.'
Also, in terms of design: I prefer to return an object, that has a key/value. The key is also a name that provides context as to what has been returned.
Returning just a string, basically a "" or {""} lacks that context ( the name of the returned variable.
Debate: Are primitive Strings Json Objects?
There seems to be also some confusion as to if a String by itself is a valid JSON document.
This confusion and debate, are quite evident in the following posts where various technical specs are mentioned: Is a primitive type considered JSON?
The only thing for sure is that a JSON object with a key-value pair is definitely valid!
As to a string by itself.. I'm not sure ( requires more reading).
Update: Answer In terms of creating/updating an entity (Post/Put)
In the specific case above, relating to such a large string that "runs into a few kilobytes"... my feeling is that this would be included within the request body.
In the specific context of sending data, I would actually be comfortable with using either 1 or 2. Additionally, 1 seems more optimized ( if your frameworks support it), since the context about what the data is, is related to the rest API method.
However, if in the future you need to add one more parameter, you will have to use a JSON entity with more than one key.
Related
I need to upload through a GraphQL mutation an object whose schema is not known at design time. Basically it is a raw JSON blob that may or may not come from other, possibly non-GraphQL services. I am using JSON scalar from https://github.com/graphql-java/graphql-java-extended-scalars:
scalar JSON
input MyInput {
jsonField: JSON
}
It works nicely except when the input blob contains keys like "$ref", which is the standard way to describe references in JSON. However, field name $ref does not seem to be accepted as it does not conform to the GraphQL naming conventions.
Obvious solutions appear to be to encode-decode field names in some way, or send the whole JSON as a String, perhaps with a custom scalar type. But is there perhaps a more elegant way to achieve this?
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."
The majority of my development experience has been from dynamically typed languages like PHP and Javascript. I've been practicing with Golang for about a month now by re-creating some of my old PHP/Javascript REST APIs in Golang. I feel like I'm not doing things the Golang way most of the time. Or more generally, I'm not use to working with strongly typed languages. I feel like I'm making excessive use of map[string]interface{} and slices of them to box up data as it comes in from http requests or when it gets shipped out as json http output. So what I'd like to know is if what I'm about to describe goes against the philosophy of golang development? Or if I'm breaking the principles of developing with strongly typed languages?
Right now, about 90% of the program flow for REST Apis I've rewritten with Golang can be described by these 5 steps.
STEP 1 - Receive Data
I receive http form data from http.Request.ParseForm() as formvals := map[string][]string. Sometimes I will store serialized JSON objects that need to be unmarshaled like jsonUserInfo := json.Unmarshal(formvals["user_information"][0]) /* gives some complex json object */.
STEP 2 - Validate Data
I do validation on formvals to make sure all the data values are what I expect before using it in SQL queries. I treat everyting as a string, then use Regex to determine if the string format and business logic is valid (eg. IsEmail, IsNumeric, IsFloat, IsCASLCompliant, IsEligibleForVoting,IsLibraryCardExpired etc...). I've written my own Regex and custom functions for these types of validations
STEP 3 - Bind Data to SQL Queries
I use golang's database/sql.DB to take my formvals and bind them to my Query and Exec functions like this Query("SELECT * FROM tblUser WHERE user_id = ?, user_birthday > ? ",formvals["user_id"][0], jsonUserInfo["birthday"]). I never care about the data types I'm supplying as arguments to be bound, so they're all probably strings. I trust the validation in the step immediately above has determined they are acceptable for SQL use.
STEP 4 - Bind SQL results to []map[string]interface{}{}
I Scan() the results of my queries into a sqlResult := []map[string]interface{}{} because I don't care if the value types are null, strings, float, ints or whatever. So the schema of an sqlResult might look like:
sqlResult =>
[0] {
"user_id":"1"
"user_name":"Bob Smith"
"age":"45"
"weight":"34.22"
},
[1] {
"user_id":"2"
"user_name":"Jane Do"
"age":nil
"weight":"22.22"
}
I wrote my own eager load function so that I can bind more information like so EagerLoad("tblAddress", "JOIN ON tblAddress.user_id",&sqlResult) which then populates sqlResult with more information of the type []map[string]interface{}{} such that it looks like this:
sqlResult =>
[0] {
"user_id":"1"
"user_name":"Bob Smith"
"age":"45"
"weight":"34.22"
"addresses"=>
[0] {
"type":"home"
"address1":"56 Front Street West"
"postal":"L3L3L3"
"lat":"34.3422242"
"lng":"34.5523422"
}
[1] {
"type":"work"
"address1":"5 Kennedy Avenue"
"postal":"L3L3L3"
"lat":"34.3422242"
"lng":"34.5523422"
}
},
[1] {
"user_id":"2"
"user_name":"Jane Do"
"age":nil
"weight":"22.22"
"addresses"=>
[0] {
"type":"home"
"address1":"56 Front Street West"
"postal":"L3L3L3"
"lat":"34.3422242"
"lng":"34.5523422"
}
}
STEP 5 - JSON Marshal and send HTTP Response
then I do a http.ResponseWriter.Write(json.Marshal(sqlResult)) and output data for my REST API
Recently, I've been revisiting articles with code samples that use structs in places I would have used map[string]interface{}. For example, I wanted to refactor Step 2 with a more standard approach that other golang developers would use. So I found this https://godoc.org/gopkg.in/go-playground/validator.v9, except all it's examples are with structs . I also noticed that most blogs that talk about database/sql scan their SQL results into typed variables or structs with typed properties, as opposed to my Step 4 which just puts everything into map[string]interface{}
Hence, i started writing this question. I feel the map[string]interface{} is so useful because majority of the time,I don't really care what the data is and it gives me to the freedom in Step 4 to construct any data schema on the fly before I dump it as JSON http response. I do all this with as little code verbosity as possible. But this means my code is not as ready to leverage Go's validation tools, and it doesn't seem to comply with the golang community's way of doing things.
So my question is, what do other golang developers do with regards to Step 2 and Step 4? Especially in Step 4...do Golang developers really encourage specifying the schema of the data through structs and strongly typed properties? Do they also specify structs with strongly typed properties along with every eager loading call they make? Doesn't that seem like so much more code verbosity?
It really depends on the requirements just like you have said you don't require to process the json it comes from the request or from the sql results. Then you can easily unmarshal into interface{}. And marshal the json coming from sql results.
For Step 2
Golang has library which works on validation of structs used to unmarshal json with tags for the fields inside.
https://github.com/go-playground/validator
type Test struct {
Field `validate:"max=10,min=1"`
}
// max will be checked then min
you can also go to godoc for validation library. It is very good implementation of validation for json values using struct tags.
For STEP 4
Most of the times, We use structs if we know the format and data of our JSON. Because it provides us more control over the data types and other functionality. For example if you wants to empty a JSON feild if you don't require it in your JSON. You should use struct with _ json tag.
Now you have said that you don't care if the result coming from sql is empty or not. But if you do it again comes to using struct. You can scan the result into struct with sql.NullTypes. With that also you can provide json tag for omitempty if you wants to omit the json object when marshaling the data when sending a response.
Struct values encode as JSON objects. Each exported struct field
becomes a member of the object, using the field name as the object
key, unless the field is omitted for one of the reasons given below.
The encoding of each struct field can be customized by the format
string stored under the "json" key in the struct field's tag. The
format string gives the name of the field, possibly followed by a
comma-separated list of options. The name may be empty in order to
specify options without overriding the default field name.
The "omitempty" option specifies that the field should be omitted from
the encoding if the field has an empty value, defined as false, 0, a
nil pointer, a nil interface value, and any empty array, slice, map,
or string.
As a special case, if the field tag is "-", the field is always
omitted. Note that a field with name "-" can still be generated using
the tag "-,".
Example of json tags
// Field appears in JSON as key "myName".
Field int `json:"myName"`
// Field appears in JSON as key "myName" and
// the field is omitted from the object if its value is empty,
// as defined above.
Field int `json:"myName,omitempty"`
// Field appears in JSON as key "Field" (the default), but
// the field is skipped if empty.
// Note the leading comma.
Field int `json:",omitempty"`
// Field is ignored by this package.
Field int `json:"-"`
// Field appears in JSON as key "-".
Field int `json:"-,"`
As you can analyze from above information given in Golang spec for json marshal. Struct provide so much control over json. That's why Golang developer most probably use structs.
Now on using map[string]interface{} you should use it when you don't the structure of your json coming from the server or the types of fields. Most Golang developers stick to structs wherever they can.
Given: I have two structs of the same type, conforming to Codable Protocol.
The structs can be multi-level (nested properties, surely also are conforming to Codable). The type is not known at the time of implementation, so i consider it generic, conforming to Codable.
One object is "base" (say, received from server), second (actually the copy of "base"), but modified inside application.
The intention is: To send a request for saving new data, but sending only the "diff" of two structs. So, only the fields, that are different should be present in resulting JSON.
The straightforward way with getting JSON strings for both structs and manipulating with them, is understandable, but seem to be the last-chance approach...
I've tried the approach with Mirror, and recursion, but now have managed to make it work only for first level - on the second level of nesting i've lost the type of nested property (if struct or array), and cannot cast it right then...
I wonder if it can be made somehow with custom encoder?
P.S.: the generic type should have all properties as Optionals, so should not provide any explicit initializers.
Instead of your "last-chance approach" -- matching JSON strings -- you could use JSONSerialization.jsonObject to convert the JSON data to Foundation objects and perform your comparison on that higher level of abstraction (if that's what you meant in your question in the first place, then sorry - nevermind).
Of course you'd pay an extra penalty of converting your Codable objects to data and then parsing that data into an object hierarchy.
I'm using JsonCpp v0.6.0 to parse the following JSON string:
{
"3.7":"de305d54-75b4-431b-adb2-eb6b9e546011",
"3.7":"de305d54-75b4-431b-adb2-eb6b9e546012",
"3.8":"de305d54-75b4-431b-adb2-eb6b9e546013"
}
as follows:
Json::Value root;
Json::Reader reader;
// value contains the JSON string
if (!reader.parse(value, root, false))
{
// parse error
}
After the call to parse, root contains two entries in a map:
[0] first = "3.7", second = "de305d54-75b4-431b-adb2-eb6b9e546012",
[1] first = "3.8", second = "de305d54-75b4-431b-adb2-eb6b9e546013",
i.e. the first JSON record has been overwritten by the second. No errors are reported.
Is this behaviour expected? Is it correct?
I thought that an error might have been reported indicating that there is a duplicate key in the JSON string.
Like the JSON RFC sad the object names (keys) should be unique.
The names within an object SHOULD be unique.
Also the RFC defines if they are not, the behavior is unpredictable.
See this quote from the RFC:
An object whose names are all unique is interoperable in the sense
that all software implementations receiving that object will agree on
the name-value mappings. When the names within an object are not
unique, the behavior of software that receives such an object is
unpredictable. Many implementations report the last name/value pair
only. Other implementations report an error or fail to parse the
object, and some implementations report all of the name/value pairs,
including duplicates.
I agree with what you say, but I think JsonCpp tries to be a helpful tool, not something that tries to scrape by with minimal conformance to the RFCs.
It would make more sense if it either maintained the structure of the input stream, and supported duplicate keys, or (and this is what the OP and I'd expect) if it doesn't like it, to flag an error.
Silently changing the structure is unhelpful, as a check for the validity of the JSON input would have to be made with some other JSON tool prior to sending it to JsonCpp.