Passing context to custom serializer through ObjectMapper

[jcbodnar]

I have an annotation that uses a custom serializer:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@JacksonAnnotationsInside
@JsonSerialize(using = MaskingSerializer.class)
    public @interface JsonMask {
}

And the serializer:

public class MaskingSerializer extends JsonSerializer<String> {

    @Override
    public void serialize(String value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        jsonGenerator.writeString(RegExUtils.replaceAll(value, ".", "*"));
    }
}

I only want the serializer to replace the String with * only some of the time. I was hoping there was a way to provide context to the ObjectMapper that would then be useable by the serializer.

I tried:

SerializationConfig serializationConfig = objectMapper.getSerializationConfig();
serializationConfig.getAttributes().withAttribute(MaskingSerializer.JSON_MASK_ENABLED_ATTRIBUTE, Boolean.TRUE);
return objectMapper
    .setConfig(serializationConfig)
    .valueToTree(entity);
}

and in the serializer:

if (serializerProvider.getConfig().getAttributes().getAttribute(JSON_MASK_ENABLED_ATTRIBUTE) == Boolean.TRUE) {
    jsonGenerator.writeString(RegExUtils.replaceAll(value, ".", "*"));
} else {
    jsonGenerator.writeString(value);
}

but getAttributes() always has an empty ContextAttributes. I also tried .withPerCallAttribute() and .withSharedAttribute() but neither worked.

Is there a way to pass context to a serializer through the ObjectMapper at the time of serialization?

[cowtowncoder]

You are missing an obvious access pattern:

if (serializerProvider.getAttribute(attributeName) == .... )

for some reason. Try that instead.

[jcbodnar]

I must be missing something on the other side for setting the attribute.

objectMapper
    .writer()
    .withAttribute(MaskingSerializer.JSON_MASK_ENABLED_ATTRIBUTE, Boolean.TRUE)
    .writeValueAsString(entity);

SerializerProvider serializerProvider = objectMapper.getSerializerProvider().setAttribute(MaskingSerializer.JSON_MASK_ENABLED_ATTRIBUTE, Boolean.TRUE);
        return objectMapper
                .setSerializerProvider((DefaultSerializerProvider) serializerProvider)
                .valueToTree(entity);
    }

Neither worked.

[cowtowncoder]

Your code for setting attribute looks correct to me.

But do not try calling setSerializerProvider(), that should never be done by application code.
That should not be necessary, and will typically not work as expected since mapper will create a new instance on per-writeValue() basis.
If you are trying to assign it as per above, that may be what is dropping the value?

... although, valueToTree() problematic case as it's not accessible via ObjectWriter. So that's not great

[jcbodnar]

I must've done something wrong at first because:

objectMapper
    .writer()
    .withAttribute(MaskingSerializer.JSON_MASK_ENABLED_ATTRIBUTE, Boolean.TRUE)
    .writeValueAsString(entity);

works!

I can live with writing it as a String. I was writing to JsonNode early on before I created my MaskingSerializer because I thought I was going to have to walk the tree and mask the nodes manually. The result is returned as part of an http response so it gets turned into a string anyway.

Thank you!

[cowtowncoder]

@jcbodnar Ok great!

And for the sake of completeness, wrt valueToTree() comment I made: conversions (ObjectMapper.xxxToXxx()) are tricky since they need read AND write, whereas ObjectWriter can only write (serialize), ObjectReader only read (deserialize).
Although ObjectReader does have treeToValue() because JsonNode can be traversed without serialization.

And that is problem wrt setting per-call Attributes. Which is why I have been tempted to introduce ObjectConverter type but... that gets into many other complications unfortunately. Oh well.