Immutables wrapper as string in Jackson

Question

How can I jackson serialize a wrapper type to and from a string?

I merged the following from two different examples their website. But the HostName type is serialized/deserialized as

{ "name" : "my.host.name.com" }

when I want it to be simply the string

"my.host.name.com"

Note that I have a lot of XName types, hence the use of the Immutables wrapper. So I would prefer a solution that keeps the amount of boiler plate down.

---

@Value.Immutable @AbstractName.Wrapper
public abstract class _HostName extends AbstractName { }

...

public abstract class AbstractName {

    @JsonSerialize
    @JsonDeserialize
    @Value.Style(
        // Detect names starting with underscore
        typeAbstract = "_*",
        // Generate without any suffix, just raw detected name
        typeImmutable = "*",
        // Make generated public, leave underscored as package private
        visibility = Value.Style.ImplementationVisibility.PUBLIC,
        // Seems unnecessary to have builder or superfluous copy method
        defaults = @Value.Immutable(builder = false, copy = false))
    public @interface Wrapper {}




    @Value.Parameter
    public abstract String name();

    @Override
    public String toString() { return name(); }
}

Answer 1

I've got this to work like below. There's an extra annotation on my name types. It's not my favorite, but it works.

@JsonDeserialize(as=HostName.class)
@Value.Immutable @AbstractName.Wrapper
public abstract class _HostName extends AbstractName { }

...

public abstract class AbstractName {

    @Value.Style(
        // Detect names starting with underscore
        typeAbstract = "_*",
        // Generate without any suffix, just raw detected name
        typeImmutable = "*",
        // Make generated public, leave underscored as package private
        visibility = Value.Style.ImplementationVisibility.PUBLIC,
        // Seems unnecessary to have builder or superfluous copy method
        defaults = @Value.Immutable(builder = false, copy = false))
    public @interface Wrapper {}


    @JsonValue
    @Value.Parameter
    public abstract String name();

    @Override
    public String toString() { return name(); }
}

Here's a little program to run it:

public static void main(String... args) throws IOException {
    ObjectMapper json = new ObjectMapper();

    String text = json.writeValueAsString(HostName.of("my.host.name.com"));

    System.out.println(text);

    HostName hostName = json.readValue(text, HostName.class);
    System.out.println(hostName);
}