This is not a json array - json being returned by web api

Question

I have the following json returned by web api but I'm getting the following error when trying to parse it: this is not a json array.

{
"$id": "1",
"updateTime": "2013-12-10T12:28:26.6533786+00:00",
"user": {
    "$id": "2",
    "CompanyID": 1,
    "username": "test",
    "Firstname": "test",
    "Lastname": "ing"
},
"Vehicles": {
    "$id": "3",
    "$values": [
        {
            "$id": "4",
            "VehicleID": 1,
            "CompanyID": 1,
            "VehicleReg": "123",
            "VehicleTypeID": 1,
            "VehicleDescription": ""
        },
        {
            "$id": "5",
            "VehicleID": 4,
            "CompanyID": 1,
            "VehicleReg": "456",
            "VehicleTypeID": 2,
            "VehicleDescription": ""
        },
        {
            "$id": "6",
            "VehicleID": 7,
            "CompanyID": 1,
            "VehicleReg": "789",
            "VehicleTypeID": 3,
            "VehicleDescription": ""
        }
    ]
},
"VehicleTypes": {
    "$id": "7",
    "$values": [
        {
            "$id": "8",
            "VehicleTypeID": 1,
            "VehicleType": "First Test Type",
            "CompanyID": 1
        },
        {
            "$id": "9",
            "VehicleTypeID": 2,
            "VehicleType": "Second Test Type",
            "CompanyID": 1
        },
        {
            "$id": "10",
            "VehicleTypeID": 3,
            "VehicleType": "Third Test Type",
            "CompanyID": 1
        }
    ]
},
"Questions": {
    "$id": "11",
    "$values": [
        {
            "$id": "12",
            "QuestionID": 1,
            "SectionID": 1,
            "CompanyID": 1,
            "Question": "Question 1"
        },
        {
            "$id": "13",
            "QuestionID": 2,
            "SectionID": 1,
            "CompanyID": 1,
            "Question": "Question 2"
        },
        {
            "$id": "14",
            "QuestionID": 3,
            "SectionID": 1,
            "CompanyID": 1,
            "Question": "Question 3"
        }
    ]
},
"QuestionSections": {
    "$id": "15",
    "$values": [
        {
            "$id": "16",
            "SectionID": 1,
            "CompanyID": 1,
            "SectionName": "Section 1"
        }
    ]
}

}

I have put this through a parser and it does say it's valid json.

I'm trying to parse the Vehicles in the json like so:

Gson gsonv = new Gson();
JsonParser parser = new JsonParser();               
JsonArray Jarray = (JsonArray)parser.parse(reader).getAsJsonArray();
ArrayList<VehicleEntity> lcs = new ArrayList<VehicleEntity>();
for(JsonElement obj : Jarray )
{
VehicleEntity v = gsonv.fromJson( obj , VehicleEntity.class);
lcs.add(v);
Log.d(TAG, "Vehicles: " + v.VehicleID);
}

My VehicleEntity matches the properties in the json Vehicles portion.

Am I on the right path here or is it a problem with the json returned by the web api?

Thanks Paul

I never used gson so may be i'm wrong, but the first nod you have is not a json array, in fact none of the root elements are jsonarrays — TootsieRockNRoll
– TootsieRockNRoll, Commented Dec 13, 2013 at 15:29

Matt · Accepted Answer · 2013-12-13 15:30:37Z

1

The top-level JSON is a JSONObject (surrounded by {}, with keys) not a JSONArray (surrounded by [], basically a list).

It sounds like you're expecting an array of these Objects, but it doesn't look like that's what you're getting.

If you wrap that object in '[' and ']' you'd have an array of length 1, and maybe your code would work.

There are sometimes server settings that send a single Object instead of a JSONArray if there is only 1 element. Maybe that's the case? What if you preform a server query that returns multiple results? Then does your code work?

answered Dec 13, 2013 at 15:30

Matt

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5 Comments

paul Over a year ago

looking at the json there are 3 vehicles I just wasn't expecting $ids $ values: tags and maybe this is the problem? Can I point the parser to give me back Vehicles/values? because after that is wher the objects are surrounded with []. Not at computer to test at moment but do you think this would work? Thanks

Matt Over a year ago

Yes, "$values" is a valid JSONArray... If you're asking how to get the vehicles array from the top-level JSONObject, it's probably something like this (untested): Gson gsonv = new Gson(); JsonParser parser = new JsonParser(); JsonObject topJsonObject = (JsonArray)parser.parse(reader).getAsJsonObject(); JsonArray jsonArray = topJsonObject.getJsonObject("Vehicles").getJsonArray("$values");

paul Over a year ago

yeah tried that but compiler doesn't like: JsonObject topJsonObject = (JsonArray)parser.parse(reader).getAsJsonObject(); Cannot convert from JsonArray to JsonObject.

paul Over a year ago

If I run the following code JsonObject userObj = (JsonObject)parser.parse(reader).getAsJsonObject().get("user"); it will give me back a user object yet if I run JsonObject topJsonObject = (JsonObject)parser.parse(reader).getAsJsonObject().get("Vehicles"); I receive an error Not a JSON Object: null. Any thoughts?

paul Over a year ago

got it working it was a stupid error on my part, basically I was reading the input stream as follows JsonObject userObj = (JsonObject)parser.parse(reader).getAsJsonObject().get("user"); but when I tried to get the 'Vehicles' like so: JsonObject vehObj = (JsonObject)parser.parse(reader).getAsJsonObject().get("Vehicles"); I was getting endOfInput = true which was causing 'Not a JSON Object' error. If I read it like so JsonObject topObj = (JsonObject)parser.parse(reader).getAsJsonObject(); I can then use topObj to get the vehicles. Thanks for your help.

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