java - jackson 特定字段名称

Question

我有这门课:

@Data
public class DiscountDto {

    @JsonProperty(required = true)
    private DiscountType type;

    @JsonProperty(required = true)
    private double discountValue;
}

DiscountType 是枚举:

public enum  DiscountType {

    PERCENT, AMOUNT
}

我想根据枚举值将 discountValue 序列化为特定值。如果枚举具有值PERCENT，则discountValue必须序列化为percent_off。如果枚举的值为 AMOUNT，则 discountValue 必须序列化为 amount_off。我怎么可能这么做？

预期结果:

如果类型== AMOUNT，我想要discountValue name = amount_off

"discountDto": {
    "amount_off": "11.0",
    "type": "AMOUNT"
}

如果类型== PERCENT，我想要discountValue name = percent_off

"discountDto": {
    "percent_off": "11.0",
    "type": "PERCENT"
}

Answer 1

可能的解决方案:

1.创建一个同时包含DiscountType和discountValue的构造函数，并直接设置percentOff或amountOff字段的值:

@JsonInclude(Include.NON_NULL)
public class DiscountDto {

     private DiscountType type;

     @JsonProperty("percent_off")
     private Double percentOff;

     @JsonProperty("amount_off")
     private Double amountOff;

     public DiscountDto(DiscountType type, double discountValue){
          this.type = type;
          if(type.equals(DiscountType.PERCENT)){
              this.percentOff = discountValue;
          }else {
              this.discountOff = discountValue;
          }

     }
     //getters and setters
}

2.使用自定义 JSON 序列化器:

public class DiscountDtoSerializer extends StdSerializer<DiscountDto> {

    public DiscountDtoSerializer() {
        this(null);
    }

    public DiscountDtoSerializer(Class<DiscountDto> t) {
        super(t);
    }

    @Override
    public void serialize(DiscountDto value, JsonGenerator jgen, SerializerProvider provider)
      throws IOException, JsonProcessingException {

        jgen.writeStartObject();
        jgen.writeNumberField("type", value.getDiscountType());
        if(value.getDiscountType().equals(DiscountType.PERCENT)){
            jgen.writeStringField("percent_off", value.getDiscountValue());
        }else{
            jgen.writeStringField("amount_off", value.getDiscountValue());
        }
        jgen.writeEndObject();
    }
 }

并且您的 ObjectMapper 应该有这个新的序列化器:

 ObjectMapper mapper = new ObjectMapper();
 SimpleModule module = new SimpleModule();
 module.addSerializer(DiscountDto.class, new DiscountDtoSerializer());
 mapper.registerModule(module);