How to customize json wrapped key for class if I am not able to mark that class with annotation JsonTypeInfo?

Question

I have code like this:

import org.codehaus.jackson.map.*;

public class MyPojo {
    int id;
    public int getId()
    { return this.id; }

    public void setId(int id)
    { this.id = id; }

    public static void main(String[] args) throws Exception {
        MyPojo mp = new MyPojo();
        mp.setId(4);
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(SerializationConfig.Feature.WRAP_ROOT_VALUE, true);        
        System.out.println(mapper.writeValueAsString(mp));
    }
}

It works expected:

{"MyPojo":{"id":4}}

But I want to customize that name. I am not able to mark MyPojo with @JsonTypeInfo becausee i take this class from library.

Is there way to do it in jackson?

Tried to subclass your `MyPojo` and adding the annotation to the subclass? — Usagi Miyamoto, Oct 29 '18 at 12:55
@Usagi Miyamoto, it is a good idea but I am not sure if we could do it because our classes are generated via thrift and we can't change signatures. — gstackoverflow, Oct 29 '18 at 12:58

score 2 · Accepted Answer · answered Oct 29 '18 at 13:12

2

You can use ObjectWriter also specifically for this class:

MyPojo mp = new MyPojo();
mp.setId(4);
ObjectMapper mapper = new ObjectMapper();
ObjectWriter writer = mapper.writer().withRootName("TestPojo");
System.out.println(writer.writeValueAsString(mp));

answered Oct 29 '18 at 13:12

Sukhpal Singh

2,130
9
20

Good idea. Do you have smth like this about deserialization? – gstackoverflow Oct 29 '18 at 13:19
You can use `mapper.reader().withRootName("TestPojo").forType(MyPojo.class)` – Sukhpal Singh Oct 29 '18 at 13:44
If root name is always going to be same, then yes. Rest depends on use case. – Sukhpal Singh Oct 29 '18 at 13:46
I need a solution which will work the same after next invocation of **mapper.reader()** – gstackoverflow Oct 29 '18 at 13:52

score 0 · Answer 2 · answered Oct 29 '18 at 12:59

0

Instead of using SerializationConfig.Feature.WRAP_ROOT_VALUE you could just create a new class like this:

public class MyWrapper {

    private MyPojo myName = new MyPojo();

    public void setId(int id) { myName.setId(id); }
}

If you create a JSON out of an object of this type, the attribute will have the name myName, e.g.: {"myName" : {"id" : 4} }.

answered Oct 29 '18 at 12:59

markusw

1,975
16
28

I am not able to do it – gstackoverflow Oct 29 '18 at 13:18
My classes generated by thrift – gstackoverflow Oct 29 '18 at 13:19

How to customize json wrapped key for class if I am not able to mark that class with annotation JsonTypeInfo?

2 Answers2