Ignore specific node within array when comparing two JSON in Java



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

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);
    }


Source: stackoverflow