set Jackson ObjectMapper class not to use scientif

问题:

I am using a library com.fasterxml.jackson library for JsonSchema, I am creating creating an IntegerSchema object, when I set range for integer schema using below code:

main(){
     IntegerSchema intSchema = new IntegerSchema();
     // setMaximum accepts Double object 
     intSchema.setMaximum(new Double(102000000));
     // setMaximum accepts Double object
     intSchema.setMinimum(new Double(100));

     printJsonSchema(intSchema);
}


public void printJsonSchema(JsonSchema schema){
        ObjectMapper mapper = new ObjectMapper();
        try {
            logger.info(mapper.writeValueAsString(schema));
        } catch (JsonProcessingException e) {
            throw new IllegalStateException(e);
        }
}

When I convert IntegerSchema to string using ObjectMapper getting below response:

{"type":"integer","maximum":1.02E8,"minimum":100.0}

maximum and minimum values are getting converted to scientific notation.

But I need output in non scientific notation as below:

{"type":"integer","maximum":102000000,"minimum":100}

I cannot change IntegerSchema class.

Please suggest how to get required output without extending IntegerSchema class?

Thanks in advance

回答1:

this is a java issue somewhat I believe. If you debug your program, your Double will always be displayed scientifically, so what we'll want is to force it into a String. This can be achieved in Java in multiple ways, and you can look it up here:

How to print double value without scientific notation using Java?

In terms of your specific question about Jackson, I've written up some code for you:

public class ObjectMapperTest {

    public static void main(String[] args) throws JsonProcessingException {

        IntegerSchema schema = new IntegerSchema();
        schema.type = "Int";
        schema.max = 10200000000d;
        schema.min = 100d;

        ObjectMapper m = new ObjectMapper();

        System.out.println(m.writeValueAsString(schema));

    }

    public static class IntegerSchema {

        @JsonProperty
        String type;
        @JsonProperty
        double min;
        @JsonProperty
        @JsonSerialize(using=MyDoubleDesirializer.class)
        double max;
    }

    public static class MyDoubleDesirializer extends JsonSerializer<Double> {


        @Override
        public void serialize(Double value, JsonGenerator gen, SerializerProvider serializers)
                throws IOException, JsonProcessingException {
            // TODO Auto-generated method stub

            BigDecimal d = new BigDecimal(value);
            gen.writeNumber(d.toPlainString());
        }

    }

}

The trick is to register a custom Serializer for your Double value. This way, you can control what you want.

I am using the BigDecimal value to create a String representation of your Double. The output then becomes (for the specific example):

{"type":"Int","min":100.0,"max":10200000000}

I hope that solves your problem.

Artur

回答2:

Feature.WRITE_BIGDECIMAL_AS_PLAIN set this for your Object Mapper