Jackson 序列化 Optional 与 YAML 的空值 [英] Jackson serialising Optional with null value for YAML

问题描述

目前我正在使用 YAMLFactory 进行配置ObjectMapper 序列化和反序列化 Pojos <=>YAML，尽管尝试了 Jackson 中的常用技巧，但它在序列化中写入了 null 值.

Currently I am using the YAMLFactory to configure the ObjectMapper to serialise and deserialise Pojos <=> YAML, however it writes null values in serialisation despite attempting the usual tricks in Jackson.

在类级别或字段级别使用 @JsonInclude(JsonInclude.Include.NON_NULL) 进行注释没有影响.我还尝试使用 @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL) 注释类，但也没有任何影响.使用 YAMLFactory 时如何实现这一点?

Annotating with @JsonInclude(JsonInclude.Include.NON_NULL) on the class level or the field level has no affect. I have also tried annotating classes with @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL) with no affect either. How do you achieve this when using the YAMLFactory?

我发现了一个类似的问题，但用例确实如此似乎不一样.明确地说，我试图完全省略该字段.

I have found a similar question but the use case does not appear to be the same. To be clear I am trying to omit the field altogether.

这是一个例子(我也在使用 Lombok)

Here is an example (I am also using Lombok)

@Data
@SuperBuilder
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode(callSuper = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
public class QueueProperties extends Properties {

    @JsonProperty("QueueName")
    private String queueName;

    @JsonProperty("RedrivePolicy")
    private RedrivePolicy redrivePolicy;

    public Optional<RedrivePolicy> getRedrivePolicy() {
        return Optional.ofNullable(redrivePolicy);
    }
}

序列化时:

Properties:
  QueueName: 471416d1-3643-4d5a-a033-65f22757dcaf-chargeback-paypal-ingestion-ingest_dispute
  RedrivePolicy: null

ObjectMapper 配置:

ObjectMapper configuration:

ObjectMapper mapper = new ObjectMapper(new YAMLFactory().enable(YAMLGenerator.Feature.MINIMIZE_QUOTES));                                                          
mapper.registerModule(new Jdk8Module());

推荐答案

getRedrivePolicy getter 方法总是返回 not-null 对象，即使如此，Optional 可以引用 null.在这种情况下，您应该跳过 empty 对象.Optional 和 null 被认为是空的，我们可以使用 JsonInclude.Include.NON_EMPTY 作为它.您可以在类级别保留 @JsonInclude(JsonInclude.Include.NON_NULL) 并仅为给定的 getter 添加 NON_EMPTY :

getRedrivePolicy getter method always returns not-null object, even so, Optional could reference to null. In this case, you should skip empty objects. Optional with null is considered as empty and we can use JsonInclude.Include.NON_EMPTY for it. You can keep @JsonInclude(JsonInclude.Include.NON_NULL) on class level and add NON_EMPTY only for given getter:

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public Optional<Object> getRedrivePolicy() {
    return Optional.ofNullable(redrivePolicy);
}

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