Cannot deserialize instance of MyEnum out of START_OBJECT token - jackson

Question

Stuck with the problem of MyEnum enum deserialization from JSON to POJO and cannot figure out what I do wrong. So basically I try to retrieve some data calling particular microservice endpoint that returns the following json:
{
"id": "9cabf3e9-965d-4407-b62b-c57dd6006419",
"myEnums": [
{
"context": "SOME_FOO_CONTEXT_1",
"feature": "SOME_BAR_FEATURE_1",
"name": "SOME_FOO_BAR_1"
},
{
"context": "SOME_FOO_CONTEXT_2",
"feature": "SOME_BAR_FEATURE_2",
"name": "SOME_FOO_BAR_2"
}
],
"name": "Some name",
"updatedBy": null,
"updated": "2019-05-16T00:11:19.279Z"
}
This is the method that calls another microservice endpoint, deserialize response body to POJO and return result as Set:
private Mono<Set<MyEnum>> fetchMyEnums(UUID someId) {
return webClient.get().uri("/v1/something/{id}", someId)
.retrieve()
.bodyToMono(MyClass.class)
.flatMapIterable(MyClass::getMyEnums)
.collect(toSet());
}
The class that used for JSON deserialization:
#lombok.Value
static class MyClass {
List<MyEnum> myEnums;
}
Enum that I actually cannot deserialize:
#Getter
#RequiredArgsConstructor
#AllArgsConstructor
#JsonFormat(shape = JsonFormat.Shape.OBJECT)
public enum MyEnum {
SOME_FOO_BAR_1(SOME_FOO_CONTEXT_1, SOME_BAR_FEATURE_1),
SOME_FOO_BAR_2(SOME_FOO_CONTEXT_2, SOME_BAR_FEATURE_2);
private final FooEnum context;
private final BarEnum feature;
private String name;
#JsonProperty
public String getName() {
return super.name();
}
}
During deserialization I receive the following exception:
org.springframework.core.codec.DecodingException: JSON decoding error: Cannot deserialize instance of `com.learn.common.security.model.MyEnum` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `com.learn.common.security.model.MyEnum` out of START_OBJECT token
at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: com.learn.common.security.service.MyEnumService$MyClass["myEnums"]->java.util.ArrayList[0])
Where I did mistake?

Answer 1

So spending few more hours to clarify what's the problem with deserialization i figure out that there is no automatic deserialization for Enum whose Shape.Object.
But I found workaround how to deserialize MyEnum object from json(you need define static method marked it as JsonCreator and define what input parameter you expect to catch from object defining JsonProperty with fieldName):
#Getter
#RequiredArgsConstructor
#AllArgsConstructor
#JsonFormat(shape = JsonFormat.Shape.OBJECT)
public enum MyEnum {
SOME_FOO_BAR_1(SOME_FOO_CONTEXT_1, SOME_BAR_FEATURE_1),
SOME_FOO_BAR_2(SOME_FOO_CONTEXT_2, SOME_BAR_FEATURE_2);
private final FooEnum context;
private final BarEnum feature;
private String name;
#JsonProperty
public String getName() {
return super.name();
}
#JsonCreator
public static MyEnum fromJson(#JsonProperty("name") String name) {
return valueOf(name);
}
}

Answer 2

For sake of completeness: You can add the #JsonCreator annotation either to a constructor or to a factory method.
Constructor:
#JsonCreator
public MyEnum(#JsonProperty("name") String name) {
this.name = name;
}
Factory method:
#JsonCreator
public static MyEnum fromJson(#JsonProperty("name") String name) {
return valueOf(name);
}
Multiple parameters:
If your enum type contains multiple properties, add them to the signature with #JsonProperty annotation.
#JsonCreator
public MyEnum(#JsonProperty("id") String id, #JsonProperty("name") String name) {
this.id = id;
this.name = name;
}
When using a factory method, creation from JSON might fail, if you have defined multiple properties. You may get this error message:
Unsuitable method [...] decorated with #JsonCreator (for Enum type [...])
Some versions of Jackson cannot handle this case. Use constructor method as a workaround, if your enum type contains more than one property.