Spring-data-elasticsearch: cannot convert from Flux<SearchHit<Sugestao>> to Flux<Sugestao> after updated to 7.6.2. How deal with SearchHit? - spring-boot

Question

Context: I want to use ElasticSearch in a full reactive stack compound by ElasticSearch and Spring WebFlux.
It is my first time using springframework.data.elasticsearch.client.reactive.ReactiveElasticsearchClient and springframework.data.elasticsearch.core.ReactiveElasticsearchOperations. I have worked in a reactive stack using MongoDb but it is my first time with ElasticSearch.
I have successfully follow a tutorial using ReactiveElasticsearchOperations with spring-data-elasticsearch-3.2.6 and elasticsearch-6.8.7 (Elastic Tutorial)
And the findAll/findById are working properly with elastic-6.8.7 and spring-data-elasticsearch-3.2.6
MyModelService:
...
private final ReactiveElasticsearchOperations reactiveElasticsearchOperations;
private final ReactiveElasticsearchClient reactiveElasticsearchClient;
public MyModelServiceImpl(ReactiveElasticsearchOperations reactiveElasticsearchOperations,
ReactiveElasticsearchClient reactiveElasticsearchClient) {
this.reactiveElasticsearchOperations = reactiveElasticsearchOperations;
this.reactiveElasticsearchClient = reactiveElasticsearchClient;
}
#Override
public Mono<MyModel> findMyModelById(String id){
return reactiveElasticsearchOperations.findById(
id,
MyModel.class,
MYMODEL_ES_INDEX,
DEFAULT_ES_DOC_TYPE
).doOnError(throwable -> logger.error(throwable.getMessage(), throwable));
}
#Override
public Flux<MyModel> findAllMyModels(String field, String value){
NativeSearchQueryBuilder query = new NativeSearchQueryBuilder();
if (!StringUtils.isEmpty(field) && !StringUtils.isEmpty(value)) {
query.withQuery(QueryBuilders.matchQuery(field, value));
}
return reactiveElasticsearchOperations.find(
query.build(),
MyModel.class,
MYMODEL_ES_INDEX
).doOnError(throwable -> logger.error(throwable.getMessage(), throwable));
}
I try follow same idea with updated versions (spring-data-elasticsearch-4 and elast-7.6.2. Since I can read "Deprecated. since 4.0, use search(Query, ...) Flux emitting matching entities one by one wrapped in a SearchHit." then I got completely stuck because the result is wrraped in SearchHit. Well, searching around I din't get the idea why such wrrapper neither how to convert/map/flatMap/etc to a Flux of my model to return by controller method.
Here is my tentative causing the issue mentioned on this question topic:
service:
import com.poc.favoritos.model.Sugestao;
import org.elasticsearch.index.query.QueryBuilders;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.elasticsearch.client.reactive.ReactiveElasticsearchClient;
import org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations;
import org.springframework.data.elasticsearch.core.query.NativeSearchQueryBuilder;
import org.springframework.util.StringUtils;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
public class SugestaoServiceImpl implements SugestaoService{
private static final Logger logger = LoggerFactory.getLogger(SugestaoServiceImpl.class);
private final ReactiveElasticsearchOperations reactiveElasticsearchOperations;
private final ReactiveElasticsearchClient reactiveElasticsearchClient;
public SugestaoServiceImpl(ReactiveElasticsearchOperations reactiveElasticsearchOperations,
ReactiveElasticsearchClient reactiveElasticsearchClient) {
this.reactiveElasticsearchOperations = reactiveElasticsearchOperations;
this.reactiveElasticsearchClient = reactiveElasticsearchClient;
}
#Override
public Mono<Sugestao> findSugestaoById(String id) {
return reactiveElasticsearchOperations.get(id, Sugestao.class)
.doOnError(throwable -> logger.error(throwable.getMessage(), throwable));
}
#Override
public Flux<Sugestao> findAllMySugestoes(String field, String value) {
NativeSearchQueryBuilder query = new NativeSearchQueryBuilder();
if (!StringUtils.isEmpty(field) && !StringUtils.isEmpty(value)) {
query.withQuery(QueryBuilders.matchQuery(field, value));
}
return reactiveElasticsearchOperations.search(query.build(), Sugestao.class);
}
}
ElastiSearchConfig orinally copied from Same tutorial mentioned above . Honestly, I am not sure why do I need and what is this config adding to my project. BTW, I am studding it also from operations reference.
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.elasticsearch.client.ClientConfiguration;
import org.springframework.data.elasticsearch.client.reactive.ReactiveElasticsearchClient;
import org.springframework.data.elasticsearch.client.reactive.ReactiveRestClients;
import org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations;
import org.springframework.data.elasticsearch.core.ReactiveElasticsearchTemplate;
import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
import org.springframework.data.elasticsearch.core.convert.MappingElasticsearchConverter;
import org.springframework.data.elasticsearch.core.mapping.SimpleElasticsearchMappingContext;
import org.springframework.web.reactive.function.client.ExchangeStrategies;
#Configuration
public class ElasticsearchConfig {
#Bean
public ReactiveElasticsearchClient reactiveElasticsearchClient() {
ClientConfiguration clientConfiguration = ClientConfiguration.builder()
.connectedTo(elassandraHostAndPort)
.withWebClientConfigurer(webClient -> {
ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder()
.codecs(configurer -> configurer.defaultCodecs()
.maxInMemorySize(-1))
.build();
return webClient.mutate().exchangeStrategies(exchangeStrategies).build();
})
.build();
return ReactiveRestClients.create(clientConfiguration);
}
#Bean
public ElasticsearchConverter elasticsearchConverter() {
return new MappingElasticsearchConverter(elasticsearchMappingContext());
}
#Bean
public SimpleElasticsearchMappingContext elasticsearchMappingContext() {
return new SimpleElasticsearchMappingContext();
}
#Bean
public ReactiveElasticsearchOperations reactiveElasticsearchOperations() {
return new ReactiveElasticsearchTemplate(reactiveElasticsearchClient(), elasticsearchConverter());
}
#Value("${spring.data.elasticsearch.client.reactive.endpoints}")
private String elassandraHostAndPort;
}

Answer 1

As for the SearchHit: This class contains information form a search result that is not part of the entity, but part of the search result like score, sort values, highlight entries.
If you don't need this and just want to have a Flux with the entity alone:
Flux<SearchHit<Entity>> fluxSearchHits = ...
Flux<Entity> fluxEntity = fluxSearchHits.map(searchHit -> searchHit.getContent);
As for the configuration:
you need the ReactiveElasticsearchClient bean to configure Spring Data Elasticsearch. The other 3 beans: Don't know why they are there; they are not needed for Spring Data Elasticsearch 4.0
Edit 16.05.2020:
The configuration: You should derive your configuration class from AbstractReactiveElasticsearchConfiguration, then you don't need the other beans, because the base class defines the necessary things:
#Configuration
public class ElasticsearchConfig extends AbstractReactiveElasticsearchConfiguration{
#Value("${spring.data.elasticsearch.client.reactive.endpoints}")
private String elassandraHostAndPort;
#Bean
public ReactiveElasticsearchClient reactiveElasticsearchClient() {
ClientConfiguration clientConfiguration = ClientConfiguration.builder()
.connectedTo(elassandraHostAndPort)
.build();
return ReactiveRestClients.create(clientConfiguration);
}
}
and the customized WebClientConfiguration is only needed if you retrieve large result sets and the default memory size for the result buffer is too low.