Jackson中带有一个字段的类/记录/值对象的平面JSON

Question

我有一个Java记录，只有一个字段：

public record AggregateId(UUID id) {}

和一个具有AggregateId字段的类(为了可读性，删除了其他字段(

public class Aggregate {
public final AggregateId aggregateId;
@JsonCreator
public Aggregate(
@JsonProperty("aggregateId") AggregateId aggregateId
) {
this.aggregateId = aggregateId;
}
}

上面的实现序列化和反序列化JSON，并给出了一个示例：

ObjectMapper objectMapper = new ObjectMapper();
String content = """
{
"aggregateId": {
"id": "3f61aede-83dd-4049-a6ff-337887b6b807"
}
}
""";
Aggregate aggregate = objectMapper.readValue(content, Aggregate.class);
System.out.println(objectMapper.writeValueAsString(aggregate));

我如何更改Jackson配置以替换JSON：

{
"aggregateId": "3f61aede-83dd-4049-a6ff-337887b6b807"
}

而不放弃AggregateId的单独类和通过字段的访问，而不使用getter？

我尝试了@JsonUnwrapper注释，但这导致抛出

Exception in thread "X" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: 
Invalid type definition for type `X`: 
Cannot define Creator parameter as `@JsonUnwrapped`: combination not yet supported at [Source: (String)"{
"aggregateId": "3f61aede-83dd-4049-a6ff-337887b6b807"
}"

或

Exception in thread "X" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: 
Cannot define Creator property "aggregateId" as `@JsonUnwrapped`: 
combination not yet supported at [Source: (String)"{
"aggregateId": "3f61aede-83dd-4049-a6ff-337887b6b807"
}"

Jackson版本：2.13.1

dependencies {
compile "com.fasterxml.jackson.core:jackson-annotations:2.13.1"
compile "com.fasterxml.jackson.core:jackson-databind:2.13.1"
}

当然，使用自定义序列化程序/反序列化程序是可能的，但我正在寻找一个更简单的解决方案，因为我有许多不同的类都有类似的问题

Answer 1

还不支持@JsonUnwrapped和@JsonCreator的组合，因此我们可以生成这样的解决方案：

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonUnwrapped;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import java.util.UUID;
public class AggregateTest {
static record AggregateId(@JsonProperty("aggregateId") UUID id) {}
static class Aggregate {
@JsonUnwrapped
@JsonProperty(access = JsonProperty.Access.READ_ONLY)
public final AggregateId _aggregateId;
public final String otherField;
@JsonCreator
public Aggregate(@JsonProperty("aggregateId") UUID aggregateId,
@JsonProperty("otherField") String otherField) {
this._aggregateId = new AggregateId(aggregateId);
this.otherField = otherField;
}
}
public static void main(String[] args) throws JsonProcessingException {
String rawJson =
"{"aggregateId": "1f61aede-83dd-4049-a6ff-337887b6b807"," +
""otherField": "İsmail Y."}";
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
Aggregate aggregate = objectMapper
.readValue(rawJson, Aggregate.class);
System.out.println(objectMapper
.writeValueAsString(aggregate));
}
}

这里我们简单地去掉@JsonUnwrapped字段。

我们获得名为aggregateId的UUID，并创建一个AggregateId记录。

关于它的详细解释：

• https://github.com/FasterXML/jackson-databind/issues/1467
• https://github.com/FasterXML/jackson-databind/issues/1497