如何在不同地方为同一Java枚举使用不同的Jackson JsonSerializers？

Question

In a JEE application, I created an enumeration with some custom label strings for the GUI:

public enum MyThing 
{
    THING1("Label 1"),
    ...
    THING5("Label 5");

    private String label;

    private MyThing(String label)
    {
        this.label = label;
    }
    ...
}

Objects with attributes of this enum type get delivered over a REST API. The attribute values get serialized as string IDs, wich is what I need:

Class with enum attribute:

public class MyBO
{
    private MyThing thing;
    ...
}

Service class:

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
...

@Path("/bos")
public class MyBOsService
{
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public BO getBO()
    {
        BO bo = new BO();
        ...
        return bo;
    }
}

REST call result:

{"thing":"THING1",...}

Great! Now, however, I'd like to also deliver a complete list of IDs and labels through a different REST service class:

@Path("/masterdata")
public class MasterDataService
{
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public MyThing[] allMyThings()
    {
        return MyThing.values();
    }
}

Desired REST call result:

[{"THING1":"Label 1"},{"THING2":"Label 2"}, ...]

I created a custom Jackson JsonSerializer to serialize the enum values as id-label pairs:

import org.codehaus.jackson.map.JsonSerializer;
...

public class MyThingSerializer extends JsonSerializer<MyThing>
{
    @Override
    public void serialize(MyThing myThing, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException
    {
    ...
    }
}

But now, I cannot find a sensible place to attach this JsonSerializer through an @JsonSerialize annotation. If I attach it to the enum like

@JsonSerialize(using = MyThingSerializer.class)
public enum MyThing{...

all enum values get serialized as id-label pairs, which is wrong for all REST calls but one.

If I attach it to the method supposed to deliver the list of id-value pairs, nothing happens:

@Path("/masterdata")
public class MasterDataService
{
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @JsonSerialize(using = MyThingSerializer.class)
    public MyThing[] allMyThings()
    {
        return MyThing.values();
    }
}

REST call result:

["THING1","THING2",...]

I know that I could attach the "id-label serializer" to the enum itself and then attach another serializer that restores the default serialization again to all other occurences of the enum, but is there a smarter way to achieve the desired different serializations in the different spots?

Answer 1

You can specify per-property custom serializers using @JsonSerialize(using=MySerializer.class) .

In case of List s and arrays, you will need to use:

@JsonSerialize(contentsUsing=MySerializer.class)

since using would replace serializer used for List or array itself; for values a different serializer is used.