如何比较Java中JsonObject的空值

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.

Answer 1

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);
    }

Answer 2

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

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

In my json, I have :

"Id":null

Answer 3

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

Answer 4

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){
  ...
}

Answer 5

试试下面的代码。

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

Answer 6

尝试使用下一个代码

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

Answer 7

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.