Builder and Jackson

[Roberto Lo Giacco]

Hi lads,

I'm trying to use Lombok and JacksonMapper together and I've found a suboptimal solution to a couple of issues I've encountered, but I believe either I'm not seeing a proper solution or there might be a couple of solutions Lombok might be able to implement.

Let me describe the issue first.

I wish to use value objects when sending data out via Jackson, so I would like to use the @Value annotation on my model objects, but at the same time, I wish to use the same objects for Jackson serialization/deserialization.

To allow easy data manipulation of my value objects I also use the @Builder and @Wither annotation on my model objects.

I know I need the @AllArgsConstructor for the @Builder, so that is added as well.

To instruct Jackson to use the builder I need to add an annotation to the generated builder class, but there is no option for that, like the onMethod = @__({ annotations } available for @Getter/@seter, etc...Something like onType would help here.

Missing that feature I've opted for letting Jackson use the default constructor (@NoArgsConstructor on my model objects), in violation of the value objects principle, but not having setters will make this default constructor pretty useless: it's still somewhat valid.

Am I missing anything? Is there another way I didn't see through which I can use Lombok with Jackson?

[Martin Grajcar]

On Sun, Nov 5, 2017 at 11:08 PM, Roberto Lo Giacco <rlog...@gmail.com> wrote:

Hi lads,

I'm trying to use Lombok and JacksonMapper together and I've found a suboptimal solution to a couple of issues I've encountered, but I believe either I'm not seeing a proper solution or there might be a couple of solutions Lombok might be able to implement.

Let me describe the issue first.

I wish to use value objects when sending data out via Jackson, so I would like to use the @Value annotation on my model objects, but at the same time, I wish to use the same objects for Jackson serialization/deserialization.

To allow easy data manipulation of my value objects I also use the @Builder and @Wither annotation on my model objects.

I know I need the @AllArgsConstructor for the @Builder, so that is added as well.

To instruct Jackson to use the builder I need to add an annotation to the generated builder class, but there is no option for that, like the onMethod = @__({ annotations } available for @Getter/@seter, etc...Something like onType would help here.

AFAIK this can be done by adding a nested Builder class and annotating it. Lombok will see it and use instead of generating.

 

Missing that feature I've opted for letting Jackson use the default constructor (@NoArgsConstructor on my model objects), in violation of the value objects principle, but not having setters will make this default constructor pretty useless: it's still somewhat valid.

AFAIK @NoArgsConstructor(access=AccessLevel.PRIVATE) would be fine. It's a very tiny violation as nobody can use directly and Jackson AFAIK uses reflection.

 

Am I missing anything? Is there another way I didn't see through which I can use Lombok with Jackson?

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[yawkat]

Just use a (public) @AllArgsConstructor. Jackson supports deserializing such objects since 2.7.0.

[Zeno Grandi]

I have successfully implemented the pattern, there is just one trick necessary: as Maartin said you need to manually add an (empty) builder class matching Lombok's, and then annotate it with @JsonPOJOBuilder.

Example:

@Value

@Builder

@JsonDeserialize(builder = MyClass.MyClassBuilder.class)

public static class MyClass {

    @NonNull private final String nonNullProperty;

    private final String nullableProperty;

    @JsonPOJOBuilder(withPrefix = "") static class MyClassBuilder {}

}