Jackson自定义序列化与反序列化注解详解

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@JsonDeserialize(using = DecimalFormatJsonDeserializer.class)
public @interface DecimalFormat{
  int scale() default 2;
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@JacksonAnnotationsInside
@JsonDeserialize(using = DecimalFormatJsonDeserializer.class)
public @interface DecimalFormat{
    int scale() default 2;
}

public static class DecimalFormatJsonDeserializer extends JsonDeserializer<Double> {

    @Override
    public Double deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JacksonException {
        // 获取当前反序列化的对象类型
        Class<?> clazz = jsonParser.getCurrentValue().getClass();
        BigDecimal decimalValue = jsonParser.getDecimalValue();
        Field declaredField;
        try {
            // 通过字段名称获取对应字段
            // 需考虑继承情况
            declaredField = clazz.getDeclaredField(jsonParser.getCurrentName());
        } catch (NoSuchFieldException e) {
            return decimalValue.doubleValue();
        }
        // 获取注解
        DecimalFormat annotation = declaredField.getAnnotation(DecimalFormat.class);
        if (annotation == null) {
            return decimalValue.doubleValue();
        }
        int scale = annotation.scale();
        if (decimalValue != null) {
            return decimalValue.setScale(scale, RoundingMode.HALF_UP).doubleValue();
        }
        return null;
    }
}

@Data
static class TestVo {
    @DecimalFormat(scale = 1)
    private Double amount;

    private String name;
}

public static void main(String args[]) throws Exception {
    ObjectMapper objectMapper = new ObjectMapper();
    TestVo testVo = objectMapper.readValue("{\"amount\":3.5576,\"name\":\"young\"}", TestVo.class);
    System.out.println(testVo); // TestVo(amount=3.6, name=young)
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@JacksonAnnotationsInside
@JsonSerialize(using = DecimalFormatJsonSerializer.class)
public @interface DecimalSerializerFormat {

    String pattern() default "0.0000";
}

public class DecimalFormatJsonSerializer extends JsonSerializer<BigDecimal> {
    @Override
    public void serialize(BigDecimal bigDecimal, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        JsonStreamContext outputContext = jsonGenerator.getOutputContext();
      	// 获取当前class对象
        Class<?> clazz = outputContext.getCurrentValue().getClass();
      	// 获取当前属性名
        String fieldName = outputContext.getCurrentName();
      	// 获取当前属性的field
        Field field = FieldUtils.getDeclaredField(clazz, fieldName, true);
      	// 获取当前属性的注解
        DecimalSerializerFormat annotation = field.getAnnotation(DecimalSerializerFormat.class);
        if (annotation == null) {
            return;
        }
        String pattern = annotation.pattern();
        DecimalFormat decimalFormat = new DecimalFormat(pattern);
        jsonGenerator.writeString(decimalFormat.format(bigDecimal));
    }
}

public static void main(String[] args) throws JsonProcessingException {
    Test test = new Test();
    test.setDecimal(BigDecimal.ONE);
    ObjectMapper objectMapper = new ObjectMapper();
    String s = objectMapper.writeValueAsString(test);
    System.out.println(s); // {"decimal":"1.0000"}
}

@Data
static class Test{
    @DecimalSerializerFormat
    private BigDecimal decimal;
}