How to remove null keys from JSON Object

Question

I have the below JSON , i need to remove all the keys which have null value

I have tried this

import java.util.Iterator;
import org.json.JSONException;
import org.json.JSONObject;
public class Remove {
    public static void main(String[] args) throws JSONException {
    String str = "{\r\n" + 
            "       \"videos\": {\r\n" + 
            "   
            "       }}";
        JSONObject json_obj = new JSONObject(str);
        JSONObject allKeys_json=    json_obj.getJSONObject("videos");
        Iterator<String> keys = allKeys_json.keys();
        while( keys.hasNext() ) {
        String keyanme = (String)keys.next();
        String keyvalue = allKeys_json.getString(keyanme);
        if(keyvalue.contains("null"))
        {
            System.out.println(keyanme+"\t"+keyvalue);
            json_obj.remove(keyanme);
        }
        }
    System.out.println(allKeys_json);
    }
}

but the actual json is unaffected , could you please tell me how to do this .

You could try: JSONObject putOpt(String name, Object value) Equivalent to put(name, value) when both parameters are non-null; does nothing otherwise. — malarres
– malarres, Commented Feb 9, 2017 at 12:21

Olivier Tonglet · Accepted Answer · 2017-02-09 12:58:17Z

3

If it's only about manipulating a string which structure you know well a solution would be to use some regex

str.replaceAll(".*\": null(,)?\\r\\n", "");

It could be easier to find a good regex than to invest time in building a model that could be used by Jackson.

Three notes:

the code above doesn't figure out which is the last line and adapt the json accordingly.
the pattern should be compiled separately.
org.json is very inefficient compared to Jackson.

answered Feb 9, 2017 at 12:58

Olivier Tonglet

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4 Comments

Olivier Tonglet Over a year ago

@NikunjParadva as mentionned in my answer :-)

Nikunj Paradva Over a year ago

Yes but got any solutions?

Olivier Tonglet Over a year ago

@NikunjParadva you could try this regex I just googled kaspars.net/blog/dev/regex-remove-all-line-breaks-from-text or google for another one. Let me know once you find the solution. The answer here is that using a Json manipulation library would be more cumbersome than manipulating the json string with a regex.

Nikunj Paradva Over a year ago

Sure i ll try and inform you soon

Thanga · Accepted Answer · 2017-02-09 12:33:21Z

1

Check your null value like this

if(keyvalue == null)

This fixex the issue

answered Feb 9, 2017 at 12:33

Thanga

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Comments

Xin Meng · Accepted Answer · 2017-02-09 12:27:38Z

0

Firstly, create an model class which is corresponding to the JSON string.

Add

@JsonIgnoreProperties(ignoreUnknown = true)

to your model class such as

@JsonIgnoreProperties(ignoreUnknown = true) 
public class Video  {
    //the properties
}

http://www.baeldung.com/jackson-deserialize-json-unknown-properties

answered Feb 9, 2017 at 12:27

Xin Meng

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1 Comment

Xin Meng Over a year ago

github.com/FasterXML/jackson-annotations/wiki/…

Suhail Mehgal · Accepted Answer · 2017-02-09 12:34:38Z

0

Use Jackson API and use @JsonInclude(Include.NON_NULL) on your model/DTO class to remove.

Like

@JsonInclude(Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown=true)
public class Video  {
    //the properties
}

answered Feb 9, 2017 at 12:34

Suhail Mehgal

1

1 Comment

AxelH Over a year ago

Use Jackson API it is a bit extrem to redirect to a different API (if I am not mistaken, this doesn't look like Jackson) just to remove Null value ;-)

MCR · Accepted Answer · 2023-10-11 09:15:53Z

0

thx!

Here is an improved regex expression that also works for an formatted and unformatted JSON string:

 str.replaceAll(" *\"\\w+\"*:(\\s)?null(,)?(\\r)?(\\n)?", "");

answered Oct 11, 2023 at 9:15

MCR

1

Comments

Syscall · Accepted Answer · 2021-04-01 18:18:15Z

-2

I used it like this and it worked for me.

@JsonInclude(value = Include.NON_NULL)

edited Apr 1, 2021 at 18:18

Syscall

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answered Apr 1, 2021 at 17:46

Vivek Gulati

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