Jackson-databind: Allow serialization of `BigDecimal` as String, using `@JsonFormat(shape=Shape.String)`, config overrides

[cen1]

When REST API is consumed by JavaScript, in order to prevent the loss of precision, BigDecimal is normally passed as a string. While adding a custom serializer is easy, I think this is a very common case and warrants an out of the box SerializationFeature.

[cowtowncoder]

This is bit too granular thing, at this point, as I would hope to avoid adding new non-general SerializationFeatures. But there is @JsonFormat already, with shape property (Shape.STRING) that should work.

It may be used on specific properties, but also via "configOverrides" for type; something like

mapper.configOverrides(BigDecimal.class).
   .setFormat(JsonFormat.Value.forShape(JsonFormat.Shape.STRING));

If this does not yet work (it requires support from serializer), it should be added.
I'll leave this open for verification if anyone has time.

[cen1]

That seems reasonable enough. I'll test on monday and come back.

[cowtowncoder]

@cen1 Thanks. And thank you for reporting this; I agree that this is important use case for javascript clients.

[cowtowncoder]

Ok while conversion does work for primitive types, it is not yet supported for BigInteger or BigDecimal. Needs to be added.

[hashhar]

@cowtowncoder I cannot see anywhere what method is called on the BigDecimal to convert it to a string? Is it toPlainString(), toString() or toEngineeringString()?

[cowtowncoder]

@hashhar what are you trying to achieve, specifically? Method will be either injackson-core (at low-level JsonGenerator implementation), or within jackson-databind. In latter case, it'd be in BigDecimalAsStringSerializer defined as inner class of NumberSerializer.

[hashhar]

I want to control how the BigDecimal gets converted into a string when using the JsonFormat.Shape support. For some BigDecimals I might want to use toPlainString() (think while dumping into a CSV) while for some I might be okay with toString()/toEngineeringString().

I found the code and it looks like we even have a config for it as StreamWriteFeature.WRITE_BIGDECIMAL_AS_PLAIN.

For other people who come across this, see the code at https://github.com/FasterXML/jackson-databind/blob/master/src/main/java/com/fasterxml/jackson/databind/ser/std/NumberSerializer.java#L127

[cowtowncoder]

Ok. Yes, at some point it may make sense to write a custom serializer: with createContextual() you have access to configuration and annotation information, including format settings.