Support `@JsonFormat` for `String`, numbers, using String.format()

Seems like it would be nice to just support formats available via format Strings that String.format() uses. Note that existing support for date/time values use different formatting; this should be fine, and if we want to for some reason support something from java.text.Format it should be possible to use heuristics to determine intended type of format. However that may not be necessary.

Initially we should just support simple types:

• java.lang.String
• int, long, short, byte, float, double and matching wrapper types
• BigDecimal, BigInteger

[mincong-h]

Hi @cowtowncoder , does this issue mean supporting the use-case below, where @JsonFormat is used to contextualize the serialization?

   static class IntAsThousandSeparatedString {
       @JsonFormat(shape=Shape.STRING, pattern="%,d")
       @JsonProperty("value")
       public int foo = 3_000;
   }

And it should be serialized as follow:

{ "value" : "3,000" }

I understand that it should support other numeric types and different locales as well. I would like to contribute on this one. If you could give me some hints about where to get started, that will be great.

[Ikki-Dai]

Hope this feature can be implement, spring framework has a @NumberFormat annotation provide similar feature!