How to compare null value from the JsonObject in java

Question

stackoverflow member i need some help from you.

I am having a JsonObject given below

{
"Id": null,
"Name": "New Task",
"StartDate": "2010-03-05T00:00:00",
"EndDate": "2010-03-06T00:00:00",
"Duration": 1,
"DurationUnit": "d",
"PercentDone": 60,
"ManuallyScheduled": false,
"Priority": 1,
"parentId": null,
"index": 2,
"depth": 1,
"checked": null }

i am getting parentId as null. I want to replace the parentId value from null to 0.

I am trying to do it with below mentioned code

if(jsonObject.get("parentId") == null || jsonObject.get("parentId") == "")
    {
        System.out.println("inside null");
        jsonObject.put("parentId", 0);
    }
    else
    {
        System.out.println("inside else part");
        //jsonObject.put("parentId", jsonObject.getInt("parentId"));
        jsonObject.put("parentId", 0);
    }

but it seems not to be working. What I am doing wrong here.

What happens with the json object after the code is executed? What is the output prom the System.out.printlns? Is JsonObject requirement or just the Json parser you chose? — Boris Strandjev, Jan 10 '12 at 11:38
i am not getting any output. but before if condition if i put the **System.out.println("JSON OBJECT VALUE FOR PARENTID ::"+jsonObject.get("parentId"));** i am getting the printout value as **null** so i want to check it using if condition but it always goes to else part only. Don't know what's the problem in this — yaryan997, Jan 10 '12 at 11:46
"i am not getting any output" what do you mean? Either you get the println from the 'then' case or from the 'else' one. — Viruzzo, Jan 10 '12 at 11:56

score 137 · Accepted Answer · edited Mar 19 '21 at 03:52

137

Use the following method of JsonObject to check if a value against any key is null

public boolean isNull(java.lang.String key)

This method is used to check Null against any key or if there is no value for the key.

check this in the documentation

Your Modified code should be like this

if(jsonObject.isNull("parentId"))
    {
        System.out.println("inside null");
        jsonObject.put("parentId", 0);
    }
    else
    {
        System.out.println("inside else part");
        //jsonObject.put("parentId", jsonObject.getInt("parentId"));
        jsonObject.put("parentId", 0);
    }

edited Mar 19 '21 at 03:52

Community

1
1

answered Jan 10 '12 at 11:46

Rajesh Pantula

10,061
9
43
52

thanks for your reply but my jsonlib-2.2.3.jar doesn't have **isNull** method declaration in it. so how to compare nll object form json data. ?? – yaryan997 Jan 16 '12 at 04:12
3

In jsonlib-2.2.3.jar, check net.sf.json.util.JSONUtils class has isNull method – Rajesh Pantula Jan 16 '12 at 06:35
4

yes.. rao i did it using JSONUtils class **boolean jsonUtils = JSONUtils.isNull(jsonObject.get("parentId"));** thanx for your support – yaryan997 Jan 16 '12 at 06:41
@RajeshPantula this is not working in `json.simple.*` what to be use in `json.simple` – Kasun Siyambalapitiya Jan 20 '17 at 07:01

score 5 · Answer 2 · answered Apr 19 '17 at 09:38

5

For com.google.gson.JsonObject, I followed this :

boolean isIdNull = jsonObject.get("Id").isJsonNull();

In my json, I have :

"Id":null

answered Apr 19 '17 at 09:38

AndroidGuy

1,270
4
15
32

score 5 · Answer 3 · answered Jan 10 '12 at 11:50

5

if(jsonObject.isNull("parentId")){
    jsonObject.put("parentId", 0);
}

answered Jan 10 '12 at 11:50

this is not working in `json.simple.*` what to be use in `json.simple` – Kasun Siyambalapitiya Jan 20 '17 at 07:03

score 3 · Answer 4 · answered Sep 07 '20 at 05:46

3

For anyone using org.json.JSONObject in 2020, if you have {"key":null}

Check the value of the key by JSONObject.NULL

JSONObject json = new JSONObject("{"key":null}");
Object value = json.get("key");
if (value == JSONObject.NULL){
  ...
}

answered Sep 07 '20 at 05:46

BabyishTank

1,329
3
18
39

2

JSONObject.NULL was the answer I was looking for, thank you. – klmlfl Oct 09 '20 at 11:56

score 1 · Answer 5 · answered Jan 10 '12 at 11:49

1

Try the following codes.

if(jsonObject.isNull("parentId") || jsonObject.get("parentId").equals(""))

answered Jan 10 '12 at 11:49

Yu Sun corn

616
6
8

this is not working in `json.simple.*` what to be use in `json.simple` – Kasun Siyambalapitiya Jan 20 '17 at 07:04

yoAlex5 · Answer 6 · 2019-08-06T10:35:19.547

0

Try to use the next code

int parentId = jsonObject.optInt("parentId", 0)

edited Aug 06 '19 at 10:35

answered Aug 06 '19 at 10:25

yoAlex5

29,217
8
193
205

score 0 · Answer 7 · answered Dec 10 '19 at 06:03

0

These two methods works

if( jsonObject.get("parentId").equals(null) )

if( jsonObject.isNull("parentId") )

Because the JSONObject has its own Null class, so java primitive null is not same as Null() in JSONObject.

answered Dec 10 '19 at 06:03

abdul rashid

730
9
21

How to compare null value from the JsonObject in java

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