On Thu, Jan 24, 2019 at 8:39 PM pscl <petercs...@gmail.com> wrote:
>
> Hi,
>
> Here's a question I've posted on SO - crossposting here in hope of getting
> some domain-expertise.
>
>
> I have a 3rd party Lombok builder POJO, one that I cannot modify, that I want
> to serialize using jackson. Notably it does not have a NoArgsConstructor.
>
> @Data
> @Builder
> public class ExternalClass {
> private String name;
> private String data;
> // etc.
> }
>
>
> On the surface this would appear to be simple, but it is incredibly
> frustrating in practice as each possible option seems to be counteracted by a
> different complication. In essence, I'm having trouble getting an external
> Lombok builder to work with a jackson mixin.
>
>
> Lombok produces fluent setters of the style .name(String name) while
> Jackson's built-in builder deserializer expects .withName(String name).
> Lombok documentation, and recipes elsewhere such as here suggest using
> @JsonDeserialize(builder=ExternalClass.ExternalClassBuilder.class) in
> conjunction with @JsonPOJOBuilder(withPrefix="") on a predeclared inner stub
> builder. But this is not possible because the Lombok class is in an external
> library.
>
> Applying these annotations to a mixin has no effect.
As explained, that approach should work, I think, as long as mixins
are bound to targets properly (that is, value class mixin has
annotation pointing to target class; builder class mixin has overrides
for prefix name).
So I may be missing something here, but what? Is builder class not
available from sources and only materialized as part Lombok
processing?
> @JsonDeserialize(ExternalClass.ExternalClassBuilder.class)
> public abstract class ExternalClassMixin {
> @JsonPOJOBuilder(withPrefix="")
> public static ExternalClassBuilder {
> }
> }
>
>
> The only approach I've found that works is to leverage the package-access
> AllArgsConstructor created by @Builder and populate the mixin with the
> following constructor
Note that as long as annotation exists, AllArgsConstructor can even be
private, if that matters; Jackson can access it via reflection (unless
Java 11+ start blocking that or something).
>
> public abstract class ExternalClassMixin {
> @JsonCreator public ExternalClassMixin(
> @JsonProperty("name") String name,
> @JsonProperty("data") String data,
> // etc.
> ) {}
> }
>
>
> This is obviously not desirable as it requires iterating and hard-coding
> every class property explicitly, making the mixin fragile to any change in
> the external POJO.
>
> My question is - is there a robust, maintainable way to serialize this
> external builder class using Jackson without modifying it, using either a
> mixin or maybe a full blown deserializer?
If mixin-for-builder approach does not, maybe others have ideas.
One interesting thing to note is that Jackson can actually override
settings on final properties too.
So as long as there are public accessors, these would be found.
-+ Tatu +-
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