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

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

Answer 3

json4s has a handy diff function described here: https://github.com/json4s/json4s (search for Merging & Diffing) and API doc here: https://static.javadoc.io/org.json4s/json4s-core_2.9.1/3.0.0/org/json4s/Diff.html

Answer 4

This is a slightly modified version of Artavazd's answer (which is amazing btw thank you so much!). This version outputs the differences into a convenient object instead of only logging them.
import play.api.Logger
import play.api.libs.json.{JsArray, JsBoolean, JsError, JsNull, JsNumber, JsObject, JsString, JsSuccess, JsValue, Json, OFormat, Reads}
case class JsDifferences(
differences: List[JsDifference] = List()
)
object JsDifferences {
implicit val format: OFormat[JsDifferences] = Json.format[JsDifferences]
}
case class JsDifference(
key: String,
path: Seq[String],
oldValue: Option[String],
newValue: Option[String]
)
object JsDifference {
implicit val format: OFormat[JsDifference] = Json.format[JsDifference]
}
object JsonUtils {
val logger: Logger = Logger(this.getClass)
def findDiff(left: JsValue, right: JsValue, parent: String = "*", path: List[String] = List()): JsDifferences = {
val newPath = path :+ parent
if (left.getClass != right.getClass) {
logger.debug(s"Cannot compare ${left.getClass.getSimpleName} and ${right.getClass.getSimpleName} in '${getPath(newPath)}'")
JsDifferences()
} else left match {
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) =>
val arr1 = value
val arr2 = right.asInstanceOf[JsArray].value
if (arr1.length != arr2.length) {
logger.debug(s"Arrays in '${getPath(newPath)}' have different length. ${arr1.length} != ${arr2.length}")
JsDifferences()
} else JsDifferences(arr1.indices.flatMap(idx => findDiff(arr1(idx), arr2(idx), s"($idx)", newPath).differences).toList)
case leftJsObject: JsObject => {
val leftFields = leftJsObject.keys.toSeq
val rightJsObject = right.asInstanceOf[JsObject]
val rightFields = rightJsObject.fields.map { case (name, value) => name }
val keysAbsentInLeft = rightFields.diff(leftFields)
val leftDifferences = keysAbsentInLeft.map(fieldName => JsDifference(
key = fieldName, path = newPath :+ fieldName, oldValue = None, newValue = Some(rightJsObject(fieldName).toString)
))
val keysAbsentInRight = leftFields.diff(rightFields)
val rightDifferences = keysAbsentInRight.map(fieldName => JsDifference(
key = fieldName, path = newPath :+ fieldName, oldValue = Some(leftJsObject(fieldName).toString), newValue = None
))
val commonKeys = leftFields.intersect(rightFields)
val commonDifferences = commonKeys.flatMap(field => findDiff(leftJsObject(field), rightJsObject(field), field, newPath).differences).toList
JsDifferences((leftDifferences ++ rightDifferences ++ commonDifferences).toList)
}
}
}
def logIfNotEqual[T](left: T, right: T, path: Seq[String]): JsDifferences = {
if (left != right) {
JsDifferences(List(JsDifference(
key = path.last, path = path, oldValue = Some(left.toString), newValue = Some(right.toString)
)))
} else JsDifferences()
}
def getPath(path: Seq[String]): String = path.mkString("\\")
}