Jackson Objectmapper将空字符串反序列化为“ null”值

Question

Sometimes during deserialization the null is getting converted to "null". Is there a way I can avoid this?

{
    "item" : {
        "title": "null",
        "id" : "134df"
    }
}

I want it as

{
    "item" : {
        "title": null,
        "id" : "134df"
    }
}

or

{
    "item" : {
        "title": "",
        "id": "134df"
    }
}

Answer 1

You can achieve it by using Google JSON ie gson.

If you are setting null against the title, then while converting the Object to JSON at that time title will not be available in the JSON string. After that you can check a condition whether the object is available or not in the JSON and do the further task.

Here is the code spinet.

import com.google.gson.Gson;

public class JackSonObjectMapperExample {

    public static void main(String[] args){
        Item item = new Item();

        item.setId("134df");
        item.setTitle(null);

        POJOExample pojo = new POJOExample();
        pojo.setItem(item);

        Gson gson = new Gson();
        String jsonInString = gson.toJson(pojo);

        System.out.println("=================>>"+jsonInString);
    }
}

class POJOExample{
    private Item item;
    public Item getItem() {
        return item;
    }
    public void setItem(Item item) {
        this.item = item;
    }
}

class Item{
    private String title;
    private String id;
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
}

output: =================>>{"item":{"id":"134df"}}

Hope, this will help you.