java 40 lines · 8 steps

Serializing Money to JSON in Spring

A custom Jackson serializer renders JavaMoney amounts as a clean, currency-aware JSON object and wires itself into Spring.

Explained by highlit

Spring Intermediate serialization jackson money rounding dependency-injection

1import com.fasterxml.jackson.core.JsonGenerator;
2import com.fasterxml.jackson.databind.JsonSerializer;
3import com.fasterxml.jackson.databind.SerializerProvider;
4import com.fasterxml.jackson.databind.module.SimpleModule;
5import org.javamoney.moneta.Money;
6import org.springframework.context.annotation.Bean;
7import org.springframework.context.annotation.Configuration;
8 
9import java.io.IOException;
10import java.math.RoundingMode;
11 
12public class MoneySerializer extends JsonSerializer<Money> {
13 
14    @Override
15    public void serialize(Money value, JsonGenerator gen, SerializerProvider provider) throws IOException {
16        Money rounded = value.with(java.util.Currency.getInstance(value.getCurrency().getCurrencyCode())
17                .getDefaultFractionDigits() >= 0
18                ? org.javamoney.moneta.function.MonetaryOperators.rounding(RoundingMode.HALF_UP)
19                : org.javamoney.moneta.function.MonetaryOperators.rounding());
20 
21        gen.writeStartObject();
22        gen.writeStringField("currency", rounded.getCurrency().getCurrencyCode());
23        gen.writeStringField("amount", rounded.getNumberStripped().toPlainString());
24        gen.writeNumberField("minorUnits", rounded.getNumberStripped()
25                .movePointRight(rounded.getCurrency().getDefaultFractionDigits())
26                .longValueExact());
27        gen.writeEndObject();
28    }
29 
30    @Configuration
31    public static class MoneyJacksonConfig {
32 
33        @Bean
34        public SimpleModule moneyModule() {
35            SimpleModule module = new SimpleModule("MoneyModule");
36            module.addSerializer(Money.class, new MoneySerializer());
37            return module;
38        }
39    }
40}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Custom JsonSerializers give you full control over how domain types appear in JSON.
2Rounding money to its currency's fraction digits before output avoids leaking floating-point noise.
3Registering a SimpleModule as a Spring bean makes Jackson pick up custom serializers automatically.

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