Ignore specific node within array when comparing two JSON in Java

Question

I want to compare two JSON strings in Java 8 for equality, but ignore specific known nodes which contain values which are expected to be different and are a tolerated difference e.g. timestamp. Currently using JSONAssert v1.5.0 from org.SkyScreamer, I'm able to 'ignore' a number of these nodes, but cannot 'ignore' nodes within an array.

What I would like is to extend my current JSONComparator to include a Customization which has its first 'path' parameter having an array address.

JSONComparator customisedJobComparator = new CustomComparator(JSONCompareMode.NON_EXTENSIBLE,
            new Customization("id", (o1, o2) -> true),
            new Customization("appointmentBookedDate.$date", (o1, o2) -> true),
            ...
            new Customization("someArray[n].timestamp", (o1, o2) -> true) //<--- this is wrong, what is the correct way for this path address?
            );

The code below is my attempt at proving a solution; both expected/actual JSON strings are identical except for anArray[].id values. I want this test to pass, but is failing with error: java.lang.AssertionError: anArray[0] Could not find match for element {"id":"valueA"}

@Test
public void compareJsonStrIgnoringDiffInArray() {
    String errorMsg = "";
    String expectedJsonStr = "{\"anArray\": [{\"id\": \"valueA\"}, {\"colour\": \"Blue\"}]}";
    String actualJsonStr = "{\"anArray\": [{\"id\": \"valueB\"}, {\"colour\": \"Blue\"}]}";

    //Create custom comparator which compares two json strings but ignores reporting any differences for anArray[n].id values
    //as they are a tolerated difference
    Customization customization = new Customization("anArray[n].id", (o1, o2) -> true);
    JSONComparator customisedComparator = new CustomComparator(JSONCompareMode.NON_EXTENSIBLE, customization);

    JSONAssert.assertEquals(errorMsg, expectedJsonStr, actualJsonStr, customisedComparator);
}

Answer 1

After some digging in the javadoc for JSONAssert, I saw an example that used an array of objects. From that example I was able to modify your test case:

    @Test
    public void compareJsonStrIgnoringDiffInArray() throws JSONException {
        String errorMsg = "";
        String expectedJsonStr = "{\"anArray\": [{\"id\": \"valueA\"}, {\"colour\": \"Blue\"}]}";
        String actualJsonStr = "{\"anArray\": [{\"id\": \"valueB\"}, {\"colour\": \"Blue\"}]}";

        //Create custom comparator which compares two json strings but ignores reporting any differences for anArray[n].id values
        //as they are a tolerated difference

        ArrayValueMatcher<Object> arrValMatch = new ArrayValueMatcher<>(new CustomComparator(
                JSONCompareMode.NON_EXTENSIBLE,
                new Customization("anArray[*].id", (o1, o2) -> true)));

        Customization arrayValueMatchCustomization = new Customization("anArray", arrValMatch);
        CustomComparator customArrayValueComparator = new CustomComparator(
                JSONCompareMode.NON_EXTENSIBLE, 
                arrayValueMatchCustomization);
        JSONAssert.assertEquals(expectedJsonStr, actualJsonStr, customArrayValueComparator);
    }

Answer 2

In case of my requirements, need to ignore the fields businessCorrelationId present only once, effectiveStartDate present in each node of data.

{
  "messageElements": {
    "messageStatus": "SUCCESS",
    "businessCorrelationId": "a80337639eb40758",
    "errorList": []
  },
  "data": [
    {
      "referenceId": 1,
      "category": "CAT1",
      "subCategory": "SUB1",
      "effectiveStartDate": "2021-02-08T00:00:00",
      "activeFlg": true,
      "version": 1
    },
    {
      "referenceId": 2,
      "category": "CAT2",
      "subCategory": "SUB2",
      "effectiveStartDate": "2021-02-08T00:00:00",
      "effectiveEndDate": null,
      "activeFlg": true,
      "version": 1
    },
    {
      "referenceId": 3,
      "category": "CAT3",
      "subCategory": "SUB3",
      "effectiveStartDate": "2021-02-08T00:00:00",
      "activeFlg": true,
      "version": 1
    }
  ],
  "tenant": {
    "tenantId": null,
    "timeZoneOffset": null,
    "name": null
  }
}

Below code worked fine.

JSONAssert.assertEquals(expectedJson, actualJson, new CustomComparator(JSONCompareMode.LENIENT,
   new Customization("data[*].createdTimestamp", (ct1, ct2) -> true),
   new Customization("messageElements.businessCorrelationId", (c1, c2) -> true)));