I'm expecting following json format:
'{
"teamId" : 9,
"teamMembers" : [ {
"userId" : 1000
}, {
"userId" : 2000
}]
}'
If I test my code with following format:-
'{
"teaXmId" : 9,
"teamMembers" : [ {
"usXerId" : 1000
}, {
"userXId" : 2000
}]
}'
I'm parsing json value as follows:-
val userId = (request.body \\ "userId" )
val teamId = (request.body \ "teamId")
val list = userId.toList
list.foreach( x => Logger.info("x val: "+x)
It doesn't throw any error to handle. Code execution goes one. Later if I try to use teamId or userId, of course it doesn't work then.
So how to check whether parsing was done correctly or stop execution right away and notify user to provide correct json format
If a value is not found when using \, then the result will be of type JsUndefined(msg). You can throw an error immediately by making sure you have the type you expect:
val teamId = (request.body \ "teamId").as[Int]
or:
val JsNumber(teamId) = request.body \ "teamId" //teamId will be BigDecimal
When using \\, if nothing is found, then an empty List is returned, which makes sense. If you want to throw an error when a certain key is not found on any object of an array, you might get the object that contains the list and proceed from there:
val teamMembers = (request.body \"teamMembers").as[Seq[JsValue]]
or:
val JsObject(teamMembers) = request.body \ "teamMembers"
And then:
val userIds = teamMembers.map(v => (v \ "userId").as[Int])
Related
I've wrote a program which process JSON objects. Now I want to verify if I've missed something.
Is there an JSON-example of all allowed JSON structure combinations? Something like this:
{
"key1" : "value",
"key2" : 1,
"key3" : {"key1" : "value"},
"key4" : [
[
"string1",
"string2"
],
[
1,
2
],
...
],
"key5" : true,
"key6" : false,
"key7" : null,
...
}
As you can see at http://json.org/ on the right hand side the grammar of JSON isn't quite difficult, but I've got several exceptions because I've forgotten to handles some structure combinations which are possible. E.g. inside an array there can be "string, number, object, array, true, false, null" but my program couldn't handle arrays inside an array until I ran into an exception. So everything was fine until I got this valid JSON object with arrays inside an array.
I want to test my program with a JSON object (which I'm looking for). After this test I want to be feel certain that my program handle every possible valid JSON structure on earth without an exception.
I don't need nesting in depth 5 or so. I only need something in nested depth 2 or max 3. With all base types which nested all allowed base types, inside this base type.
Have you thought of escaped characters and objects within an object?
{
"key1" : {
"key1" : "value",
"key2" : [
"String1",
"String2"
],
},
"key2" : "\"This is a quote\"",
"key3" : "This contains an escaped slash: \\",
"key4" : "This contains accent charachters: \u00eb \u00ef",
}
Note: \u00eb and \u00ef are resp. charachters ë and ï
Choose a programming language that support json.
Try to load your json, on fail the exception's message is descriptive.
Example:
Python:
import json, sys;
json.loads(open(sys.argv[1]).read())
Generate:
import random, json, os, string
def json_null(depth = 0):
return None
def json_int(depth = 0):
return random.randint(-999, 999)
def json_float(depth = 0):
return random.uniform(-999, 999)
def json_string(depth = 0):
return ''.join(random.sample(string.printable, random.randrange(10, 40)))
def json_bool(depth = 0):
return random.randint(0, 1) == 1
def json_list(depth):
lst = []
if depth:
for i in range(random.randrange(8)):
lst.append(gen_json(random.randrange(depth)))
return lst
def json_object(depth):
obj = {}
if depth:
for i in range(random.randrange(8)):
obj[json_string()] = gen_json(random.randrange(depth))
return obj
def gen_json(depth = 8):
if depth:
return random.choice([json_list, json_object])(depth)
else:
return random.choice([json_null, json_int, json_float, json_string, json_bool])(depth)
print(json.dumps(gen_json(), indent = 2))
I can't understand, how can i add optional property with json transformer.
I want merge two json objects (list and calendars) without or with dynamic list of properties (for example without owner):
calendar1 = {id:1, name: "first", description:"my first calendar", owner: 1}
calendar2 = {id:2, name: "second", owner: 1}
list = [{id: 1, settings: []}, {id: 2, settings: []}]
and result must be
{calendars:
[
{id:1, name: "first", description:"my first calendar", settings: []},
{id:2, name: "second", settings: []}
]
}
I'll assume the following json trees
val calendar1 = Json.parse("""{"id":1, "name": "first", "description":"my first calendar", "owner": 1}""")
val calendar2 = Json.parse("""{"id":2, "name": "second", "owner": 1}""")
You need to add settings to each calendar, then remove the owner if it exists.
Putting a value in branch settings is explained in the documentation
val addSettings = __.json.update((__ \ "settings").json.put(Json.arr()))
Dropping the owner is also explained
val removeOwner = (__ \ "owner").json.prune
Now you can define the transformer to be applied to each of your calendar object
val transformer = addSettings andThen removeOwner
With that in place there are multiple options depending on how your data is actually modeled. If you have a Seq of calendars as in
val calendars = Seq(calendar1, calendar2)
you can do
val normalizedCalendars = calendars.map(_.transform(transformer))
This gives you a Seq[JsResult[JsObject]] which you want to transform into a JsResult[Seq[JsObject]].
I am pretty sure there is a way to do it using play's functional syntax (see play.api.libs.functional and play.api.libs.functional.syntax) but this part of play is not well documented and I haven't gotten around to studying Applicatives yet even though I have a feel for what they do.
Instead, I rely on the following code inspired by scala's Future#sequence
def sequence[A, M[X] <: TraversableOnce[X]](in: M[JsResult[A]])(implicit cbf: CanBuildFrom[M[JsResult[A]], A, M[A]]): JsResult[M[A]] = {
val empty: JsResult[mutable.Builder[A, M[A]]] = JsSuccess(cbf(in))
in.foldLeft(empty) {(jracc,jrel) => (jracc,jrel) match {
case (JsSuccess(builder,_), JsSuccess(a,p)) =>JsSuccess(builder+=a, p)
case (ra#JsError(builderErrors), re#JsError(errors)) =>JsError.merge(ra, re)
case (JsSuccess(_,_), re#JsError(errors)) => re
case (ra#JsError(builderErrors), JsSuccess(_,_)) => ra
}} map (_.result())
}
With that you can write :
val calendarArray = sequence(normalizedCalendars).map(v=>Json.obj("calendars"->JsArray(v)))
which will give you a JsResult[JsObject]. As long as your original calendars are indeed JsObjects you will get a JsSuccess. You can verify the output structure with :
calendarArray.foreach(println)
which returns :
{"calendars":[{"id":1,"name":"first","description":"my first calendar","settings":[]},{"id":2,"name":"second","settings":[]}]}
which is the same as what you asked modulo some whitespace
{
"calendars":[
{"id":1,"name":"first","description":"my first calendar","settings":[]},
{"id":2,"name":"second","settings":[]}
]
}
Start with:
scala> case class Calendar(id:Int,name:String,description:Option[String],owner:Int)
defined class Calendar
scala> case class CalendarRow(id:Int,name:String,description:Option[String],settings:Seq[String]=Seq.empty)
defined class CalendarRow
scala> def append(calendars:Calendar*) = calendars.map(c => CalendarRow(c.id,c.name,c.description))
append: (calendars: Calendar*)Seq[CalendarRow]
scala> val calendar1 = Calendar(1,"first",Option("my first calendar"),1)
calendar1: Calendar = Calendar(1,first,Some(my first calendar),1)
scala> val calendar2 = Calendar(2, "second",None,1)
calendar2: Calendar = Calendar(2,second,None,1)
scala> val list = append(calendar1,calendar2)
list: Seq[CalendarRow] = ArrayBuffer(CalendarRow(1,first,Some(my first calendar),List()), CalendarRow(2,second,None,List()))
Many thanks to #Jean and comments in "Unveiling Play 2.1 Json API - Part 3 : JSON Transformers"
It's hard understanding things like and, andThen, andKeep, keepAnd in JSON transformers for me (I can not find any detailed descriptions with examples), but i found some templates for my question:
Optional property in JSON:
With Reader
(__ \ "id").json.pick[JsString].flatMap{
case id if id.equals(JsString(accountId)) =>
(__ \ "primary").json.put(JsBoolean(true))
case _ =>
Reads.pure(Json.obj())
}
With Json.obj()
(__ \ "id").json.pick[JsString].map{
case id if id.equals(JsString(accountId)) =>
Json.obj("primary" -> true)
case _ =>
Json.obj()
}
Given a JSON array like this one:
{
"success": true,
"data": [
{
"id": 600,
"title": "test deal",
"e54cbe3a434d8e6": 54
},
{
"id": 600,
"title": "test deal",
"e54cbe3a434d8e6": 54
},
],
"additional_data": {
"pagination": {
"start": 0,
"limit": 100,
"more_items_in_collection": false
}
}
}
In my Play 2.2.2 application, using the Scala JSON Reads Combinator, everything works going this way:
implicit val entityReader = Json.reads[Entity]
val futureJson: Future[List[Entity]] = futureResponse.map(
response => (response.json \ "data").validate[List[Entity]].get
The problem now is the key named 'e54cbe3a434d8e6' which I would like to name 'value' in my object:
// This doesn't work, as one might expect
case class Entity(id: Long, title: String, e54cbe3a434d8e6: Long)
// I would like to use 'value' instead of 'e54cbe3a434d8e6'
case class Entity(id: Long, title: String, value: Long)
There is vast information about the combinators here and here but I only want to use a fieldname which is different from the key name in the JSON array. Can some one help me to find a simple way?
I suppose it has got something to do with JSON.writes?!
One simple way without trying to apply transformations on json itself is to define a custom Reads in such a way to handle this:
val json = obj(
"data" -> obj(
"id" -> 600,
"title" -> "test deal",
"e54cbe3a434d8e6" -> 54))
case class Data(id: Long, title: String, value: Int)
val reads = (
(__ \ "id").read[Long] ~
(__ \ "title").read[String] ~
(__ \ "e54cbe3a434d8e6").read[Int] // here you get mapping from your json to Scala case class
)(Data)
def index = Action {
val res = (json \ "data").validate(reads)
println(res) // prints "JsSuccess(Data(600,test deal,54),)"
Ok(json)
}
Another way is to use combinators like this:
... the same json and case class
implicit val generatedReads = reads[Data]
def index = Action {
val res = (json \ "data").validate(
// here we pick value at 'e54cbe3a434d8e6' and put into brand new 'value' branch
__.json.update((__ \ "value").json.copyFrom((__ \ "e54cbe3a434d8e6").json.pick)) andThen
// here we remove 'e54cbe3a434d8e6' branch
(__ \ "e54cbe3a434d8e6").json.prune andThen
// here we validate result with generated reads for our case class
generatedReads)
println(res) // prints "JsSuccess(Data(600,test deal,54),/e54cbe3a434d8e6/e54cbe3a434d8e6)"
Ok(prettyPrint(json))
}
I have the following Json:
{
"web-category" : "macaroons",
"sub-categories" : [
{ "name" : "pink" },
{ "name" : "blue" },
{ "name" : "green" }
]
}
I have got it in Play as a JsObject. So I can now successfully do the following:
//(o is the JsObject)
val webCat:Option[String] = (o \ "web-category").asOpt[String]
println(webCat.toString)
>> Some(macaroons)
So far, so good. But how do I access the array Json objects? I have this...
val subCats:Option[JsArray] = (o \ "sub-categories").asOpt[JsArray]
println(subCats.toString)
>> Some([{"name" : "blue"},{"name" : "green"},{"name" : "pink"}])
but what I need is to take the JsArray and get a List of all the names something like this:
List("blue", "green", "pink")
Don't know how to access the JsArray thusly.
my thanks for your help in this.
I'd argue that it's generally a good idea to move from JSON-land to native-Scala-representation-land as early as possible. If obj is your JsObject, for example, you can write this:
val subCategories = (obj \ "sub-categories").as[List[Map[String, String]]]
val names = subCategories.map(_("name"))
Or even:
case class Category(name: String, subs: List[String])
import play.api.libs.functional.syntax._
implicit val categoryReader = (
(__ \ "web-category").read[String] and
(__ \ "sub-categories").read[List[Map[String, String]]].map(_.map(_("name")))
)(Category)
And then:
obj.as[Category]
This latter approach makes error handling even cleaner (e.g. you can just replace as with asOpt at this top level) and composes nicely with other Reads type class instances—if you have a JsArray of these objects, for example, you can just write array.as[List[Category]] and get what you expect.
What Peter said, or:
(o \ "sub-categories" \\ "name").map(_.as[String]).toList
Something like this:
subCats.map( jsarray => jsarray.value.map(jsvalue => (jsvalue \ "name").as[String]).toList)
This will normally return a Option[List[String]]
I have a controller method in my Scala Play project that takes JSON as input. I would like to turn this JSON into a model object I have.
Here is my controller method:
def broadcastPost = Action(parse.json) { request =>
(request.body).asOpt[Post].map { post =>
Post.create(post.channelId, post.message, post.datePosted, post.author)
Ok(play.api.libs.json.Json.toJson(
Map("status" -> "OK", "message" -> ("Post created"))
))
}.getOrElse {
BadRequest(play.api.libs.json.Json.toJson(
Map("status" -> "Error", "message" -> ("Missing parameter [Post]"))
))
}
}
And here is the model:
case class Post(id: Pk[Long], channelId: Long, message: String, datePosted: Date, author: String)
and its implicit formatter:
implicit val postFormat = (
(__ \ "id").formatNullable[Long] and
(__ \ "channelId").format[Long] and
(__ \ "message").format[String] and
(__ \ "datePosted").format[Date] and
(__ \ "author").format[String]
)((id, channelId, message, datePosted, author) => Post(id.map(Id(_)).getOrElse(NotAssigned), channelId, message, datePosted, author),
(p: Post) => (p.id.toOption, p.channelId, p.message, p.datePosted, p.author))
When I send a POST request to that method with the following data:
{"channelId":1, "message":"Wanna get a game in?", "dateCreated":"5-15-2013", "author":"Eliot Fowler"}
I get the following response:
{"status":"Error","message":"Missing parameter [Post]"}
I am very new to Scala, so I may be overlooking something very simple here.
Instead of using asOpt, which loses the error, you should use validate, which will allow you to return the error message, and then see what the problem is, eg:
def broadcastPost = Action(parse.json) { request =>
request.body.validate[Post].fold({ errors =>
BadRequest(Json.obj(
"status" -> "Error",
"message" -> "Bad JSON",
"details" -> JsError.toFlatJson(errors)
))
}, { post =>
Post.create(post.channelId, post.message, post.datePosted, post.author)
Ok(Json.obj("status" -> "OK", "message" -> "Post created"))
})
}
Now, what I'm guessing that will tell you is that "5-15-2013" is not a valid date. The default date format for JSON in Play is yyyy-MM-dd. You can specify a custom one by modifying your format to say:
...
(__ \ "datePosted").format[Date](Format(Reads.dateReads("MM-dd-yyyy"), Writes.dateWrites("MM-dd-yyyy"))) and
...
Another built in one Reads.IsoDateReads, this is more standard than the American only month day year format, another approach that avoids this issue altogether is use a Long as milliseconds since epoch.