map json string to enum

Question

I have the following class and enums:

import lombok.Data;
// other imports...

@Data
public class MapTest{
    private MyFirstEnum myFirstEnum;
    private MySecondEnum mySecondEnum;
}

public enum MyFirstEnum{
    MY_FIRST_ENUM1,
    MY_FIRST_ENUM2
}

public enum MySecondEnum {
    MY_SECOND_ENUM1,
    MY_SECOND_ENUM2
}

and this spring controller:

@PostMapping("/testMap")
@ResponseBody
public void TestMap(@RequestBody MapTest mapTest){

}

Since an enum can be looked up by its name what I would like to do is to post a json to the controller and that the appropriate props will be serialized by their name:

{
    "myFirstEnum": "MY_FIRST_ENUM1",
    "mySecondEnum": "MY_SECOND_ENUM2"
}

I've tried to set up a @JsonDeserialize but i couldn't get the type of the enum inside the overridden function:

// what type should i use here?
public static class StringToEnum extends JsonDeserializer<???> {
    // how do i get the type of the current enum?
    @Override
    public ??? deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        ??? res = Enum.valueOf(p.getText());
        return res;
    }
}

Update: I've failed to mention that i'm using lombok's @data attribute for automatically generating getters and setters, which doesn't work well with enum bindings (not sure why).
I guess that laziness comes with a price.

Write two JsonDeserializers, once by replacing your ??? with `MyFirstEnum` and next by `MySecondEnum`, in case you still want to write custom deserializers. — Hemant Patel, May 02 '18 at 17:53
Correct me if I'm wrong, but isn't that the way Jackson handles enums *by default*? — crizzis, May 02 '18 at 18:14
Jackson handles it by default, it seems `MapTest` has setter / getter missing. — Hemant Patel, May 02 '18 at 18:16

Hemant Patel · Answer 1 · 2018-05-02T18:19:40.393

0

It should be serialized automatically via jackson but you can force it via @JsonCreator
Redefine your enums as

public enum MyFirstEnum{
    MY_FIRST_ENUM1,
    MY_FIRST_ENUM2;

    @JsonCreator
    public static MyFirstEnum fromString(String raw) {
        return MyFirstEnum.valueOf(raw.toUpperCase());
    }
}

Similarly define your second enum as well in the similar manner.

Imp Note (Mandatory)

MapTest should have public setter / getter for both enums (if declared private, preferred), or declare them public (should be avoided, not preferred)

edited May 02 '18 at 18:19

answered May 02 '18 at 17:46

Hemant Patel

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how can will i use the `fromString` function once it's declared? – Yoav May 02 '18 at 18:07
You don't need to use it, jackson library will use it. BTW you can still call MyFirstEnum.fromValue("MY_FIRST_ENUM1"). – Hemant Patel May 02 '18 at 18:09

map json string to enum

1 Answers1