使用 Jackson 将 Double 序列化为 2 个小数位 [英] Serialize a Double to 2 decimal places using Jackson

问题描述

我使用 Jackson 和 Spring MVC，将一些简单的对象写成 JSON.其中一个对象具有 amount 属性，类型为 Double.(我知道 Double 不应该用作货币金额.但是，这不是我的代码.)

I'm using Jackson, with Spring MVC, to write out some simple objects as JSON. One of the objects, has an amount property, of type Double. (I know that Double should not be used as a monetary amount. However, this is not my code.)

在 JSON 输出中，我想将数量限制为 2 位小数.目前显示为:

In the JSON output, I'd like to restrict the amount to 2 decimal places. Currently it is shown as:

"amount":459.99999999999994

我尝试过使用 Spring 3 的 @NumberFormat 注释，但在这方面没有成功.看起来其他人也有问题:MappingJacksonHttpMessageConverter 的 ObjectMapper 在将 JSON 绑定到 JavaBean 属性时不使用 ConversionService 在此处输入链接描述.

I've tried using Spring 3's @NumberFormat annotation, but haven't had success in that direction. Looks like others had issues too: MappingJacksonHttpMessageConverter's ObjectMapper does not use ConversionService when binding JSON to JavaBean propertiesenter link description here.

此外，我尝试使用带有自定义序列化程序的 @JsonSerialize 注释.
在模型中:

Also, I tried using the @JsonSerialize annotation, with a custom serializer.
In the model:

@JsonSerialize(using = CustomDoubleSerializer.class)
public Double getAmount()

和序列化器实现:

public class CustomDoubleSerializer extends JsonSerializer<Double> {
    @Override
    public void serialize(Double value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
        if (null == value) {
            //write the word 'null' if there's no value available
            jgen.writeNull();
        } else {
            final String pattern = ".##";
            //final String pattern = "###,###,##0.00";
            final DecimalFormat myFormatter = new DecimalFormat(pattern);
            final String output = myFormatter.format(value);
            jgen.writeNumber(output);
        }
    }
}

CustomDoubleSerializer似乎"起作用了.但是，任何人都可以提出任何其他更简单(或更标准)的方法来做到这一点.

The CustomDoubleSerializer "appears" to work. However, can anyone suggest any other simpler (or more standard) way of doing this.

推荐答案

我知道 Double 不应用作货币金额.然而，这不是我的代码.

I know that Double should not be used as a monetary amount. However, this is not my code.

确实不应该.BigDecimal 是存储货币金额的更好选择，因为它无损 并且可以更好地控制小数位.

Indeed, it should not. BigDecimal is a much better choice for storing monetary amounts because it is lossless and provides more control of the decimal places.

所以对于确实可以控制代码的人来说，它可以这样使用:

So for people who do have control over the code, it can be used like this:

double amount = 111.222;
setAmount(new BigDecimal(amount).setScale(2, BigDecimal.ROUND_HALF_UP));

这将序列化为 111.22.无需自定义序列化程序.

That will serialize as 111.22. No custom serializers needed.

这篇关于使用 Jackson 将 Double 序列化为 2 个小数位的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！