@JsonSerialize and @JsonDeserialize not working when included in an annotation

问题

I am trying to create a custom annotation to tokenize a given property always when it is annotated with, so I have the following structure:

@JsonComponent
public class TokenSerializer {

    @JsonSerialize(using = IdToTokenSerializer.class) // This does not work 
    @JsonDeserialize(using = TokenToIdDeserializer.class) // This does not work 
    @Retention(RetentionPolicy.RUNTIME)
    public static @interface TokenizedId {
        Class<?> value();
    }

    public static class IdToTokenSerializer extends JsonSerializer<Long> implements ContextualSerializer {
        ...
    }

    public static class TokenToIdDeserializer extends JsonDeserializer<Long> implements ContextualDeserializer {
        ...
    }
}

Why am I using like that? Because the @TokenizedId will provide a class, which conditionally will be considered on the serializer/deserializer to do something. This value is configured using the ContextualDeserializer, fetching the class from @TokenizedId.

The issue is, both serializer and deserializer do not work when I annotate just like this:

@TokenizedId(MyClass.class)
private Long id;

But they work when I use like this (removing the @JsonSerialize and @JsonDeserialize from @TokenizedId):

@JsonSerialize(using = IdToTokenSerializer.class)
@JsonDeserialize(using = TokenToIdDeserializer.class)
@TokenizedId(MyClass.class)
private Long id;

Personally I did not like this approach, since developers will need to always remember to use these three annotations when they would like to tokenize some id, and also I would like the @TokenizedId always be related to these serializers.

Is there a way to make the serializer/deserializer work when annotated on another annotation?

回答1:

I was able to make the annotation works the way I wanted, looking after some clue on the Jackson lib, I found the @JacksonAnnotationsInside annotation:

/**
 * Meta-annotation (annotations used on other annotations)
 * used for indicating that instead of using target annotation
 * (annotation annotated with this annotation),
 * Jackson should use meta-annotations it has.
 * This can be useful in creating "combo-annotations" by having
 * a container annotation, which needs to be annotated with this
 * annotation as well as all annotations it 'contains'.
 * 
 * @since 2.0
 */
@Target({ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotation
public @interface JacksonAnnotationsInside
{

}

Including this on my annotation solved the issue:

@JacksonAnnotationsInside
@JsonSerialize(using = IdToTokenSerializer.class) 
@JsonDeserialize(using = TokenToIdDeserializer.class)
@Retention(RetentionPolicy.RUNTIME)
public static @interface TokenizedId {
    Class<?> value();
}

来源：https://stackoverflow.com/questions/56853750/jsonserialize-and-jsondeserialize-not-working-when-included-in-an-annotation

标签

java

spring-boot

jackson

serialization