Comparing two JSON files using java

Question

I have two JSON files, called "pickevent1" and "pickevent2". I have to compare if both files are matching; if they don't match, I need to know where they don't match.

pickevent1

 {
     "pickEventActivities": [{
         "orderId": "215",
         "lineNbr": 0,
         "pick": "EACH",
         "activations": [{
             "activationType": "Si",
             "activationValue": "31"
         }]
      }]
  }

pickevent2

{
    "pickEventActivities": [{
        "orderId": "115",
        "lineNbr": 1,
        "pick": "Hello",
        "activations": [{
            "activationType": "Bi",
            "activationValue": "3"
        }]
    }]
}

I created a pick event POJO class:

@JsonRootName(value = "pickEventActivities")
@Data
@JsonPropertyOrder({ "orderId", "lineNbr", "pick"})
class PickEvent {
    String orderId;
    String lineNbr;
    String pick;
    List<Activation> activations;
}

and a Activation POJO class:

@Data
@JsonPropertyOrder({ "activationType", "activationValue"})
public class Activation {
    String activationType;
    String activationValue;
}

To make sure it works, I created a test class:

public void compareJson() throws Exception {
    final ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.configure(FAIL_ON_UNKNOWN_PROPERTIES, false);
    objectMapper.configure(ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
    
    PickEvent result1 = objectMapper.readValue(new File("src/../pickevent1.json"), PickEvent.class);
    PickEvent result2 = objectMapper.readValue(new File("src/../pickevent2.json"), PickEvent.class);
    
    assertEquals(result1, result2);
}

But when I am doing assertSame(result1,result2) its giving me null for json values:

Exception in thread "main" java.lang.AssertionError: expected same:<PickEvent(orderId=null, lineNbr=null, pick=null, activations=null)> was not:<PickEvent(orderId=null, lineNbr=null, pick=null, activations=null)>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotSame(Assert.java:828)
    at org.junit.Assert.assertSame(Assert.java:771)
    at org.junit.Assert.assertSame(Assert.java:782)
    at JsonDiff.PickEventDiff.comparejson(PickEventDiff.java:26)
    at JsonDiff.PickEventDiff.main(PickEventDiff.java:32)

It should give me an assertion error, but the test succeeds.

Did you override `equals()` and `hashCode()` for your POJOs? — LHCHIN, Dec 03 '21 at 07:30
You have to override `equals()` (generated by your IDE for example) so that you can compare two PickEvents based on their internal details. Please refer to [Compare two objects with .equals() and == operator](https://stackoverflow.com/questions/13387742/compare-two-objects-with-equals-and-operator). — LHCHIN, Dec 03 '21 at 07:36
@LHCHIN – You are right that `equals()` is needed to compare based on the internal details. But when the method is not overwritten, `assertEquals()` for two distinct objects should always fail. Why is it not failing here?? — tquadrat, Dec 03 '21 at 07:41
@Rumi – What happens if you replace `assertEquals()` by `assertSame()`? — tquadrat, Dec 03 '21 at 07:44
I don't understand why your test is *not* failing, but be aware Lomboks `@Data` annotation already provides the `equals()` and `hashCode()` methods! — Jacob van Lingen, Dec 03 '21 at 07:47
@tquadrat with assertSame its coming as AssertionFails but its retrieving null values for the json content. I am updating the code — Rumi, Dec 03 '21 at 08:04
Remove ```objectMapper.configure(FAIL_ON_UNKNOWN_PROPERTIES, false);```. In fact, an exception occurred during the parsing process. — zysaaa, Dec 03 '21 at 08:18
@zysaaa I removed that line and I can see the exception, none of the field is getting accepted, would you mind to paste a bit of your code, just want to check out your approach. — Rumi, Dec 03 '21 at 08:28

score 2 · Accepted Answer · answered Dec 03 '21 at 08:37

It should give me an assertion error, but the test succeeds.

Because you use objectMapper.configure(FAIL_ON_UNKNOWN_PROPERTIES, false);. In fact, an exception occurred during the parsing process.

Try:

    public void compareJson() throws Exception {
        final ObjectMapper objectMapper = new ObjectMapper();
        Wrapper wrapper = objectMapper.readValue(new File(""), Wrapper.class);
        Wrapper wrapper2 = objectMapper.readValue(new File(""), Wrapper.class);
        System.out.println(wrapper.equals(wrapper2));
    }

    @Data
    static class Wrapper {
        List<PickEvent> pickEventActivities;
    }

score 0 · Answer 2 · answered Dec 03 '21 at 08:30

You are trying to read a PickEvent Object but you're actually sending a list there.

Please change your json to

{
    "pickEventActivities": {
        "orderId": "115",
        "lineNbr": 1,
        "pick": "Hello",
        "activations": [{
            "activationType": "Bi",
            "activationValue": "3"
        }]
    }
}

or try changing your code to

List<PickEvent> list1 = objectMapper.readValue(new File("src/../pickevent1.json"), new ParameterizedTypeReference<PickEvent>(){});

score 0 · Answer 3 · answered Oct 24 '22 at 08:41

0

Here is my github repo for Intellij Idea plugin. Basically JSON comparator implemented in java. It compares JSON by fields, values and objects in array

answered Oct 24 '22 at 08:41

Volodymyr Kret

1,511
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Comparing two JSON files using java

3 Answers3