How to define JSON Schema for Map<String, Integer>?

Question

I have a json :

{
    "itemTypes": {
        "food": 22,
        "electrical": 2
    },
    "itemCounts": {
        "NA": 211
    }
}

Here the itemTypes and itemCounts will be common but not the values inside them (food, NA, electrical) which will be keep changing but the will be in the format : Map<String, Integer>

How do I define Json Schema for such generic structure ?

I tried :

"itemCounts": {
    "type": "object""additionalProperties": {
        "string",
        "integer"
    }
}

By defining the json shcema, are you asking how to write a class that represents the json? — Trevor Bye
– Trevor Bye, Commented Nov 22, 2016 at 19:45

esp · Accepted Answer · 2016-11-22 20:20:06Z

40

You can:

{
  "type": "object",
  "properties": {
    "itemType": {"$ref": "#/definitions/mapInt"},
    "itemCount": {"$ref": "#/definitions/mapInt"}
  },
  "definitions": {
    "mapInt": {
      "type": "object",
      "additionalProperties": {"type": "integer"}
    }
  }
}

answered Nov 22, 2016 at 20:20

esp

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4 Comments

Sachin Jain Over a year ago

How do we specify which of the two should be treated as "key" here ?

Jared Forsyth Over a year ago

Keys will always be strings in JSON. both itemType and itemCount in this example are maps of "string" to "integer". Also note that you don't have to use the definitions thing in order to make a map of string to int -- that's just a shortcut used in this example to deduplicate definitions.

ttugates Over a year ago

I am searching for how to represent Map<number, number>. I control server and client and thus serializers, but can't figure out how to define the key as a number, any help?

Brendan Samek Over a year ago

@ttugates You won't be able to do that in JSON schema since it's that doesn't conform to the JSON specification

franleplant · Accepted Answer · 2021-11-19 00:07:41Z

The question is kind of badly described, let me see if I can rephrase it and also answer it.

Question: How to Represent a map in json schema like so Map<String, Something>

Answer:

It looks like you can use Additional Properties to express it https://json-schema.org/understanding-json-schema/reference/object.html#additional-properties

{
  "type": "object",
  "additionalProperties": { "type": "something" }
}

For example let's say you want a Map<string, string>

{
  "type": "object",
  "additionalProperties": { "type": "string" }
}

Or something more complex like a Map<string, SomeStruct>

{
  "type": "object",
  "additionalProperties": { 
    "type": "object",
    "properties": {
      "name": "stack overflow"
    }
  }
}

Jay99 · Accepted Answer · 2022-09-03 07:16:31Z

2

using "additionalProperties" has 2 problems

It creates additional class that represents Object or Int Map which internally has additionalProperty as member to be used as Map
because its additionalProperties, it always has @JsonIgnore so it wont appear while serialization.

so In my opinion, The right approach would be to use direct Java Type.

"properties": {
  "myFieldName": {
    "existingJavaType" : "java.util.Map<String,String>",
    "type" : "object"
  }
}

ref: https://www.jsonschema2pojo.org/

edited Sep 3, 2022 at 7:16

answered Feb 24, 2022 at 2:03

Jay99

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1 Comment

shubham verma Over a year ago

Do this also creates and additionalProperties variable

Roberto Caboni · Accepted Answer · 2020-07-15 15:45:21Z

-4

{
    "type": "array",
    "maxItems": 125,
    "items": {
        "type": "array",
        "items": [
            { // key schema goes here },
            { // value schema goes here }
        ],
        "additionalItems": false
    }
}

edited Jul 15, 2020 at 15:45

Roberto Caboni

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answered Jul 15, 2020 at 15:07

swarnim gupta

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1 Comment

charlag Over a year ago

This defines an array of pairs, not a map

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