How to compare null value from the JsonObject in java

问题

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.

回答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);
    }

回答2:

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

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

In my json, I have :

"Id":null

回答3:

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

回答4:

Try the following codes.

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

回答5:

Try to use the next code

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

回答6:

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.

来源：https://stackoverflow.com/questions/8802236/how-to-compare-null-value-from-the-jsonobject-in-java

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java

json

hibernate

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