How do I deserialize number to enum?

[yvasyliev]

I need to convert integer to enum.
There is a quick demo:

public class JacksonDemo {
    public static void main(String[] args) throws JsonProcessingException {
        String json = "{\"code\":6}";
        ObjectMapper mapper = new ObjectMapper();
        Note note = mapper.readValue(json, Note.class);
        System.out.println(note.code);
    }

    public static class Note {
        @JsonProperty("code")
        private Code code;

        public void setCode(Code code) {
            this.code = code;
        }
    }

    public enum Code {
        @JsonProperty("6") AA06;
    }
}

Output:

Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `io.github.yvasyliev.JacksonDemo$Code` from number 6: index value outside legal index range [0..0]
 at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); line: 1, column: 9] (through reference chain: io.github.yvasyliev.JacksonDemo$Note["code"])
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.weirdNumberException(DeserializationContext.java:1970)
	at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdNumberValue(DeserializationContext.java:1290)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._fromInteger(EnumDeserializer.java:355)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer.deserialize(EnumDeserializer.java:285)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:310)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:177)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:342)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4899)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3846)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3814)
	at io.github.yvasyliev.JacksonDemo.main(JacksonDemo.java:12)

If I do the same with Gson, the code works perfectly.

public class GsonDemo {
    public static void main(String[] args) throws JsonProcessingException {
        String json = "{\"code\":6}";
        Gson gson = new Gson();
        Note note = gson.fromJson(json, Note.class);
        System.out.println(note.code);
    }

    public static class Note {
        @SerializedName("code")
        private Code code;

        public void setCode(Code code) {
            this.code = code;
        }
    }

    public enum Code {
        @SerializedName("6") AA06;
    }
}

Output:

AA06

So how can I make it work with jackson-databind?
I'm using version 2.16.0.

[pjfanning]

This is a volunteer project. There are lots of blogs and already answered questions on stackoverflow.com. use you favourite search engine. Maybe start with https://www.baeldung.com/jackson-serialize-enums

[pjfanning]

You're happy to use Serialized name annotations but not Jackson annotations? Stick with gson.

[yvasyliev]

@SerializedName is nothing but the Gson equivalent of @JsonProperty. The difference is that Jackson ignores @JsonProperty and treats integers as enum ordinals. I wonder if I can tell Jackson not to ignore @JsonProperty.

The @JsonValue and @JsonCreator approaches are rather workarounds than solutions.

[cowtowncoder]

I don't see use of @JsonValue or @JsonCreator as a work-around but solution: rather, @JsonProperty does not quite fit since it cannot retain typing aspect (it always takes a String value, and what you show here is Number). So use of @JsonProperty is supported for String values despite its semantics being somewhat different (it is not renaming Object properties but Enum serialization).

Having said that, I thought there was some support for number representation with @JsonProperty; will see if I am mistaken there.

[cowtowncoder]

Ok, no, looks like deserialization from integer numbers is only supported wrt @JsonValue or @JsonCreator annotations.

[yvasyliev]

Ok, thanks for the confirmation @cowtowncoder