Spring Data Elasticsearch documents not being deserialized

Spring Data Elasticsearch version: 3.2.6.RELEASE
Elasticsearch version: 7.6.2

I am attempting to deserialize a list of MerchantCategory using:

SearchQuery getAllQuery = new NativeSearchQueryBuilder()
        .withQuery(matchAllQuery())
        .build();
return elasticsearchTemplate.queryForList(getAllQuery, MerchantCategory.class);

The String id field is correctly set on the list of MerchsntCategory but the other fields remain null.

I have confirmed that the documents fields are persisted in Elasticsearch using Kibana.

The field mappings are submitted to Elasticsearch when the Spring Boot application is started:

request [PUT http://127.0.0.1:9200/merchantcategory/_mapping/merchantcategory?master_timeout=30s&include_type_name=true&timeout=30s] returned 1 warnings: [299 Elasticsearch-7.6.2-ef48eb35cf30adf4db14086e8aabd07ef6fb113f "[types removal] Using include_type_name in put mapping requests is deprecated. The parameter will be removed in the next major version."]

Here is the MerchantCategory class:

@NoArgsConstructor
@AllArgsConstructor
@Builder
@Getter
@Setter
@Document(indexName = "merchantcategory", type = "merchantcategory")
public class MerchantCategory implements Serializable {

    @Id
    @JsonIgnore
    private String id;

    @SerializedName("ParentId")
    private Long parentId;

    @SerializedName("Name")
    private String name;

    @SerializedName("Description")
    private String description;

    @SerializedName("UrlName")
    private String urlName;

    @SerializedName("Id")
    private Long categoryId;

    @SerializedName("MerchantsInCategory")
    private List<MerchantCategoryRelationship> merchants;
}

I use gson to serialize:

val bulkRequest = new BulkRequest();
entities.subList(startIndex, endIndex).forEach(e ->{
    String source = gson.toJson(e);
    val indexRequest = new IndexRequest(index).source(source, XContentType.JSON).type(type);
        bulkRequest.add(indexRequest);
});

highLevelClient.bulkAsync(bulkRequest, RequestOptions.DEFAULT, getListener());

I have also tried the same thing with merchantCategoryElasticsearchRepository.findAll(); and have the same issue.

Why is it that the only field that is serialized is the String id field and not the others?

Do you use Jackson as serializer?

Than you have to use: @JsonProperty

@JsonProperty("UrlName")
private String urlName;

If you are using GSON as serializer you have to use @SerializedName.

@SerializedName("UrlName")
private String urlName;