How to find the difference/mismatch between two JSON file?

Question

I have two json files, one is expected json and the another one is the result of GET API call. I need to compare and find out the mismatch in the file.

Expected Json:

{
  "array": [
    1,
    2,
    3
  ],
  "boolean": true,
  "null": null,
  "number": 123,
  "object": {
    "a": "b",
    "c": "d",
    "e": "f"
  },
  "string": "Hello World"
}

Actual Json response:

{
  "array": [
    1,
    2,
    3
  ],
  "boolean": true,
  "null": null,
  "number": 456,
  "object": {
    "a": "b",
    "c": "d",
    "e": "f"
  },
  "string": "India"
}

Actually there are two mismatch: number received is 456 and string is India.

Is there a way to compare and get these two mismatch as results.

This need to be implemented in gatling/scala.

Answer 1

You can use, for example, play-json library and recursively traverse both JSONs. For next input (a bit more sophisticated than yours input):

LEFT:

{
  "array" : [ 1, 2, 4 ],
  "boolean" : true,
  "null" : null,
  "number" : 123,
  "object" : {
    "a" : "b",
    "c" : "d",
    "e" : "f"
  },
  "string" : "Hello World",
  "absent-in-right" : true,
  "different-types" : 123
}

RIGHT:

{
  "array" : [ 1, 2, 3 ],
  "boolean" : true,
  "null" : null,
  "number" : 456,
  "object" : {
    "a" : "b",
    "c" : "d",
    "e" : "ff"
  },
  "string" : "India",
  "absent-in-left" : true,
  "different-types" : "YES"
}

It produces this output:

Next fields are absent in LEFT: 
     *\absent-in-left
Next fields are absent in RIGHT: 
     *\absent-in-right
'*\array\(2)' => 4 != 3
'*\number' => 123 != 456
'*\object\e' => f != ff
'*\string' => Hello World != India
Cannot compare JsNumber and JsString in '*\different-types'

Code:

val left = Json.parse("""{"array":[1,2,4],"boolean":true,"null":null,"number":123,"object":{"a":"b","c":"d","e":"f"},"string":"Hello World","absent-in-right":true,"different-types":123}""").asInstanceOf[JsObject]
val right = Json.parse("""{"array":[1,2,3],"boolean":true,"null":null,"number":456,"object":{"a":"b","c":"d","e":"ff"},"string":"India","absent-in-left":true,"different-types":"YES"}""").asInstanceOf[JsObject]

// '*' - for the root node
showJsDiff(left, right, "*", Seq.empty[String])

def showJsDiff(left: JsValue, right: JsValue, parent: String, path: Seq[String]): Unit = {
  val newPath = path :+ parent
  if (left.getClass != right.getClass) {
    println(s"Cannot compare ${left.getClass.getSimpleName} and ${right.getClass.getSimpleName} " +
      s"in '${getPath(newPath)}'")
  }
  else {
    left match {
      // Primitive types are pretty easy to handle
      case JsNull => logIfNotEqual(JsNull, right.asInstanceOf[JsNull.type], newPath)
      case JsBoolean(value) => logIfNotEqual(value, right.asInstanceOf[JsBoolean].value, newPath)
      case JsNumber(value) => logIfNotEqual(value, right.asInstanceOf[JsNumber].value, newPath)
      case JsString(value) => logIfNotEqual(value, right.asInstanceOf[JsString].value, newPath)
      case JsArray(value) =>
        // For array we have to call showJsDiff on each element of array
        val arr1 = value
        val arr2 = right.asInstanceOf[JsArray].value
        if (arr1.length != arr2.length) {
          println(s"Arrays in '${getPath(newPath)}' have different length. ${arr1.length} != ${arr2.length}")
        }
        else {
          arr1.indices.foreach { idx =>
            showJsDiff(arr1(idx), arr2(idx), s"($idx)", newPath)
          }
        }
      case JsObject(value) =>
        val leftFields = value.keys.toSeq
        val rightJsObject = right.asInstanceOf[JsObject]
        val rightFields = rightJsObject.fields.map { case (name, value) => name }

        val absentInLeft = rightFields.diff(leftFields)
        if (absentInLeft.nonEmpty) {
          println("Next fields are absent in LEFT: ")
          absentInLeft.foreach { fieldName =>
            println(s"\t ${getPath(newPath :+ fieldName)}")
          }
        }
        val absentInRight = leftFields.diff(rightFields)
        if (absentInRight.nonEmpty) {
          println("Next fields are absent in RIGHT: ")
          absentInRight.foreach { fieldName =>
            println(s"\t ${getPath(newPath :+ fieldName)}")
          }
        }
        // For common fields we have to call showJsDiff on them
        val commonFields = leftFields.intersect(rightFields)
        commonFields.foreach { field =>
          showJsDiff(value(field), rightJsObject(field), field, newPath)
        }

    }
  }
}


def logIfNotEqual[T](left: T, right: T, path: Seq[String]): Unit = {
  if (left != right) {
    println(s"'${getPath(path)}' => $left != $right")
  }
}

def getPath(path: Seq[String]): String = path.mkString("\\")

Answer 2

Use diffson - a Scala implementation of RFC-6901 and RFC-6902: https://github.com/gnieh/diffson