Keep trailing zero when serializing BigDecimal to JSON

[caodangtinh]

Describe your Issue

Is there any way to keep the trailing zero value when serializing BigDecimal to JSON? I'd expect something like

"version": 2.0

But I always get

"version": 2

I have already tried with

@JsonFormat(shape = JsonFormat.Shape.NUMBER, pattern = "#.#")

And a customer, JsonSerializer

public class BigDecimalStringSerializer extends JsonSerializer<BigDecimal> {

    @Override
    public void serialize(BigDecimal value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        gen.writeNumber(value.toPlainString());
    }
}

But it is still produce the same output.

[pjfanning]

Issues are for bugs. So far, this appears just to be a usage question.

Have you tried pattern = "#.0"? I don't know for definite but BigDecimal formatting should be handled by this class
https://docs.oracle.com/javase/8/docs/api/java/text/DecimalFormat.html

And its Javadocs describe how the pattern values like '#' and '0' work.

[caodangtinh]

@pjfanning , I have tried with

@JsonFormat(shape = JsonFormat.Shape.NUMBER, pattern = "#.0")

As well as the DecimalFormat

public class BigDecimalStringSerializer extends JsonSerializer<BigDecimal> {
    @Override
    public void serialize(BigDecimal value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        var df = new DecimalFormat();
        df.setMinimumFractionDigits(value.scale());
        df.setMaximumFractionDigits(value.scale());
        df.setGroupingUsed(false);
        gen.writeNumber(df.format(value));
    }
}

However, it still got the same result, trailing zero was removed.
I'm using Jackson version 2.17.2

[pjfanning]

I tried using the JsonFormat annotation and the pattern does seem not to work.
I used format shape String but also tried Number and in both cases the pattern had no effect.
My example is in 2.18...pjfanning:jackson-databind:number-serialize-pattern

@cowtowncoder Any suggestions? I can't find any similar serialization tests where numbers are formatted using the JsonFormat annotation.

[pjfanning]

#4671 seems to show that custom serializers can be made to work.

[cowtowncoder]

Correct: @JsonFormat does not change Number serialization at this point.

But custom serializer should work, esp. if using String-taking method, writeNumber(String numStr)

[yihtserns]

...
df.setMinimumFractionDigits(value.scale());
...
However, it still got the same result, trailing zero was removed.

Likely because value.scale() returned 0. You should've just do df.setMinimumFractionDigits(1) and it would've worked.

[yihtserns]

One way to serialize with trailing zero without needing @JsonFormat nor custom JsonSerializer is to create a BigDecimal with trailing zero, e.g.:

• BigDecimal.valueOf(2.0)
• new BigDecimal("2.0")

[caodangtinh]

Nice, it does work