Need Jackson serializer for Double and need to specify precision at runtime

Question

There are many posts about creating Jackson serializers for numbers, currency, etc. For engineering applications, there is often a need to set the precision on numbers based

Answer 1

You may use Jackson's ContextualSerializer to achieve desired serialization as shown below.

Firstly, create an annotation to capture precision

@Target({ElementType.FIELD,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Precision {
    int precision();
}

Next, create a contextual serializer for Double type which looks for Precision annotation on the field to be serialized and then create a new serializer for the specified precision.

public class DoubleContextualSerializer extends JsonSerializer implements ContextualSerializer {

    private int precision = 0;

    public DoubleContextualSerializer (int precision) {
        this.precision = precision;
    }

    public DoubleContextualSerializer () {

    }

    @Override
    public void serialize(Double value, JsonGenerator gen, SerializerProvider serializers) throws IOException, JsonProcessingException {
        if (precision == 0) {
            gen.writeNumber(value.doubleValue());
        } else {
            BigDecimal bd = new BigDecimal(value);
            bd = bd.setScale(precision, RoundingMode.HALF_UP);
            gen.writeNumber(bd.doubleValue());
        }

    }
    @Override
    public JsonSerializer createContextual(SerializerProvider prov, BeanProperty property) throws JsonMappingException {
        Precision precision = property.getAnnotation(Precision.class);
        if (precision != null) {
            return new DoubleContextualSerializer (precision.precision());
        }
        return this;
    }
}

Finally, annotate your field to use custom serializer and set precision

public class Bean{

   @JsonSerialize(using = DoubleContextualSerializer .class)
   @Precision(precision = 2)
   private double doubleNumber;

}

Hope this helps!!