message.json

{
"messageId" : 633000000272,
"value" : 14.04,
"date" : "2016-11-18T15:14:58",
"target" : 125.00,
"orderId" : 9,
"gpio" : [
{
"id" : 1,
"direction" : "in",
"value" : false
},
{
"id" : 2,
"direction" : "out",
"value" : true
},
{
"id" : 3,
"direction" : "in",
"value" : false
},
{
"id" : 4,
"direction" : "in",
"value" : true
}
]
}

schema.json

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "type": "object",
  "properties": {
    "messageId": {
      "type": "integer"
    },
    "value": {
      "type": "number"
    },
    "date": {
      "type": "string",
      "format": "date-time"
    },
    "target": {
      "type": "number"
    },
    "orderId": {
      "type": "integer"
    },
    "gpio": {
      "type": "array",
      "items": [
        {
          "type": "object",
          "properties": {
            "id": {
              "type": "integer"
            },
            "direction": {
              "type": "string",
               "pattern" : "(in|out)"
            },
            "value": {
              "type": "boolean",
             
            }
          }
        }
      ]
    }
  }
}