Unexpected serialization of List<Object> fields [DATACOUCH-560]

[spring-projects-issues]

spac-valentin opened DATACOUCH-560 and commented

I have an entity without a strict structure (user can add custom fields/json objects)

@Document
public class MyClass {
    @Id
    private String id;

    @Field
    private List<Map<String, Object>> fields; 
    @Field
    private List<Map<String, Object>> configuration;

MappingCouchbaseConverter converts this into a mix of CouchbaseDocuments & CouchbaseLists and sends it to couchbase Transcoder which encodes it and stores it into DB.

Issue: JacksonJsonSerializer used by JsonTranscoder serialises the above object into

{
   "configuration":{
      "empty":false
   },
   "_class":"org.myorg.MyEntity",
   "fields":{
      "empty":false
   }
}

Workaround:
In your CouchbaseConfiguration, override configureEnvironment and provide a custom object mapper to handle this scenario

 @Override
    protected void configureEnvironment(ClusterEnvironment.Builder builder) {
        Jackson2ObjectMapperBuilder jacksonBuilder = new Jackson2ObjectMapperBuilder();
        jacksonBuilder.serializationInclusion(JsonInclude.Include.NON_NULL);

        jacksonBuilder.modules(
                new CouchbaseJacksonModule(),
                new JsonValueModule() // Don't forget to add this module provided by couchbase client
        );
        
        builder.jsonSerializer(JacksonJsonSerializer.create(objectMapper()));
        super.configureEnvironment(builder);
    }

CouchbaseJacksonModule

public class CouchbaseJacksonModule extends SimpleModule {

    public CouchbaseJacksonModule() {
        super(new Version(1, 0, 0, null, "org.myorg", "CouchbaseWorkaround"));
        addSerializer(CouchbaseDocument.class, new CouchbaseDocumentSerializer());
        addSerializer(CouchbaseList.class, new CouchbaseListSerializer());
    }

    public static class CouchbaseDocumentSerializer extends JsonSerializer<CouchbaseDocument> {

        @Override
        public void serialize(CouchbaseDocument value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
            Map<String, Object> valueContent = value.getContent();
            JsonSerializer<Object> serializer = serializers.findValueSerializer(valueContent.getClass());
            serializer.serialize(valueContent, gen, serializers);
        }
    }

    public static class CouchbaseListSerializer extends JsonSerializer<CouchbaseList> {

        @Override
        public void serialize(CouchbaseList value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
            List<Object> objects = value.export();
            JsonSerializer<Object> serializer = serializers.findValueSerializer(objects.getClass());
            serializer.serialize(objects, gen, serializers);
        }
    }
}

I was expecting this to work OOTB

---

Affects: 4.0 GA (Neumann)

Referenced from: pull request runnerway@fed0e5f

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