Add reactive SearchHits implementation.

Original Pull Request #2017
Closes #2015

Author: sothawo

Diff for: src/main/asciidoc/reference/elasticsearch-operations.adoc

@@ -144,6 +144,9 @@ Returned by the low level scroll API functions in `ElasticsearchRestTemplate`, i
 .SearchHitsIterator<T>
 An Iterator returned by the streaming functions of the `SearchOperations` interface.
 
+.ReactiveSearchHits
+`ReactiveSearchOperations` has methods returning a `Mono<ReactiveSearchHits<T>>`, this contains the same information as a `SearchHits<T>` object, but will provide the contained `SearchHit<T>` objects as a `Flux<SearchHit<T>>` and not as a list.
+
 [[elasticsearch.operations.queries]]
 == Queries
 

Diff for: src/main/java/org/springframework/data/elasticsearch/backend/elasticsearch7/ReactiveElasticsearchTemplate.java

@@ -754,6 +754,31 @@ public <T> Mono<SearchPage<T>> searchForPage(Query query, Class<?> entityType, C
 				.map(searchHits -> SearchHitSupport.searchPageFor(searchHits, query.getPageable()));
 	}
 
+	@Override
+	public <T> Mono<ReactiveSearchHits<T>> searchForHits(Query query, Class<?> entityType, Class<T> resultType) {
+		return searchForHits(query, entityType, resultType, getIndexCoordinatesFor(entityType));
+	}
+
+	@Override
+	public <T> Mono<ReactiveSearchHits<T>> searchForHits(Query query, Class<?> entityType, Class<T> resultType,
+			IndexCoordinates index) {
+
+		Assert.notNull(query, "query must not be null");
+		Assert.notNull(entityType, "entityType must not be null");
+		Assert.notNull(resultType, "resultType must not be null");
+		Assert.notNull(index, "index must not be null");
+
+		SearchDocumentCallback<T> callback = new ReadSearchDocumentCallback<>(resultType, index);
+
+		return doFindForResponse(query, entityType, index) //
+				.flatMap(searchDocumentResponse -> Flux.fromIterable(searchDocumentResponse.getSearchDocuments()) //
+						.flatMap(callback::toEntity) //
+						.collectList() //
+						.map(entities -> SearchHitMapping.mappingFor(resultType, converter) //
+								.mapHits(searchDocumentResponse, entities))) //
+				.map(ReactiveSearchHitSupport::searchHitsFor);
+	}
+
 	private Flux<SearchDocument> doFind(Query query, Class<?> clazz, IndexCoordinates index) {
 
 		return Flux.defer(() -> {
@@ -777,8 +802,9 @@ private Mono<SearchDocumentResponse> doFindForResponse(Query query, Class<?> cla
 			request = prepareSearchRequest(request, false);
 
 			SearchDocumentCallback<?> documentCallback = new ReadSearchDocumentCallback<>(clazz, index);
-
-			return doFindForResponse(request, searchDocument -> documentCallback.toEntity(searchDocument).block());
+			Function<SearchDocument, Object> entityCreator = searchDocument -> documentCallback.toEntity(searchDocument)
+					.block();
+			return doFindForResponse(request, entityCreator);
 		});
 	}
 
@@ -895,19 +921,18 @@ protected Flux<SearchDocument> doFind(SearchRequest request) {
 	 * Customization hook on the actual execution result {@link Mono}. <br />
 	 *
 	 * @param request the already prepared {@link SearchRequest} ready to be executed.
-	 * @param suggestEntityCreator
+	 * @param entityCreator
 	 * @return a {@link Mono} emitting the result of the operation converted to s {@link SearchDocumentResponse}.
 	 */
 	protected Mono<SearchDocumentResponse> doFindForResponse(SearchRequest request,
-			Function<SearchDocument, ? extends Object> suggestEntityCreator) {
+			Function<SearchDocument, ? extends Object> entityCreator) {
 
 		if (QUERY_LOGGER.isDebugEnabled()) {
 			QUERY_LOGGER.debug(String.format("Executing doFindForResponse: %s", request));
 		}
 
-		return Mono.from(execute(client1 -> client1.searchForResponse(request))).map(searchResponse -> {
-			return SearchDocumentResponse.from(searchResponse, suggestEntityCreator);
-		});
+		return Mono.from(execute(client -> client.searchForResponse(request)))
+				.map(searchResponse -> SearchDocumentResponse.from(searchResponse, entityCreator));
 	}
 
 	/**

Diff for: src/main/java/org/springframework/data/elasticsearch/backend/elasticsearch7/document/SearchDocumentResponse.java

@@ -99,12 +99,12 @@ public Suggest getSuggest() {
 	 * creates a SearchDocumentResponse from the {@link SearchResponse}
 	 *
 	 * @param searchResponse must not be {@literal null}
-	 * @param suggestEntityCreator function to create an entity from a {@link SearchDocument}
+	 * @param entityCreator function to create an entity from a {@link SearchDocument}
 	 * @param <T> entity type
 	 * @return the SearchDocumentResponse
 	 */
 	public static <T> SearchDocumentResponse from(SearchResponse searchResponse,
-			Function<SearchDocument, T> suggestEntityCreator) {
+			Function<SearchDocument, T> entityCreator) {
 
 		Assert.notNull(searchResponse, "searchResponse must not be null");
 
@@ -113,7 +113,7 @@ public static <T> SearchDocumentResponse from(SearchResponse searchResponse,
 		Aggregations aggregations = searchResponse.getAggregations();
 		org.elasticsearch.search.suggest.Suggest suggest = searchResponse.getSuggest();
 
-		return from(searchHits, scrollId, aggregations, suggest, suggestEntityCreator);
+		return from(searchHits, scrollId, aggregations, suggest, entityCreator);
 	}
 
 	/**
@@ -123,14 +123,14 @@ public static <T> SearchDocumentResponse from(SearchResponse searchResponse,
 	 * @param scrollId scrollId
 	 * @param aggregations aggregations
 	 * @param suggestES the suggestion response from Elasticsearch
-	 * @param suggestEntityCreator function to create an entity from a {@link SearchDocument}
+	 * @param entityCreator function to create an entity from a {@link SearchDocument}
 	 * @param <T> entity type
 	 * @return the {@link SearchDocumentResponse}
 	 * @since 4.3
 	 */
 	public static <T> SearchDocumentResponse from(SearchHits searchHits, @Nullable String scrollId,
 			@Nullable Aggregations aggregations, @Nullable org.elasticsearch.search.suggest.Suggest suggestES,
-			Function<SearchDocument, T> suggestEntityCreator) {
+			Function<SearchDocument, T> entityCreator) {
 
 		TotalHits responseTotalHits = searchHits.getTotalHits();
 
@@ -154,7 +154,7 @@ public static <T> SearchDocumentResponse from(SearchHits searchHits, @Nullable S
 			}
 		}
 
-		Suggest suggest = suggestFrom(suggestES, suggestEntityCreator);
+		Suggest suggest = suggestFrom(suggestES, entityCreator);
 		return new SearchDocumentResponse(totalHits, totalHitsRelation, maxScore, scrollId, searchDocuments, aggregations,
 				suggest);
 	}

Diff for: src/main/java/org/springframework/data/elasticsearch/core/ReactiveSearchHitSupport.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.core;
+
+import org.springframework.util.Assert;
+
+/**
+ * @author Peter-Josef Meisch
+ * @since 4.4
+ */
+public final class ReactiveSearchHitSupport {
+	private ReactiveSearchHitSupport() {}
+
+	public static <T> ReactiveSearchHits<T> searchHitsFor(SearchHits<T> searchHits) {
+
+		Assert.notNull(searchHits, "searchHits must not be null");
+
+		return new ReactiveSearchHitsImpl<>(searchHits);
+	}
+}

Diff for: src/main/java/org/springframework/data/elasticsearch/core/ReactiveSearchHits.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.core;
+
+import reactor.core.publisher.Flux;
+
+import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
+import org.springframework.lang.Nullable;
+
+/**
+ * Encapsulates a Flux of {@link SearchHit}s with additional information from the search.
+ *
+ * @param <T> the result data class.
+ * @author Peter-Josef Meisch
+ * @since 4.4
+ */
+public interface ReactiveSearchHits<T> {
+
+	/**
+	 * @return the aggregations.
+	 */
+	@Nullable
+	AggregationsContainer<?> getAggregations();
+
+	float getMaxScore();
+
+	/**
+	 * @return the {@link SearchHit}s from the search result.
+	 */
+	Flux<SearchHit<T>> getSearchHits();
+
+	/**
+	 * @return the number of total hits.
+	 */
+	long getTotalHits();
+
+	/**
+	 * @return the relation for the total hits
+	 */
+	TotalHitsRelation getTotalHitsRelation();
+
+	/**
+	 * @return true if aggregations are available
+	 */
+	boolean hasAggregations();
+
+	/**
+	 * @return whether the {@link SearchHits} has search hits.
+	 */
+	boolean hasSearchHits();
+
+	/**
+	 * @return the suggest response
+	 */
+	@Nullable
+	Suggest getSuggest();
+
+	/**
+	 * @return wether the {@link SearchHits} has a suggest response.
+	 */
+	boolean hasSuggest();
+}

Diff for: src/main/java/org/springframework/data/elasticsearch/core/ReactiveSearchHitsImpl.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.core;
+
+import reactor.core.publisher.Flux;
+
+import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
+import org.springframework.lang.Nullable;
+
+/**
+ * @author Peter-Josef Meisch
+ * @since 4.4
+ */
+public class ReactiveSearchHitsImpl<T> implements ReactiveSearchHits<T> {
+
+	protected final SearchHits<T> delegate;
+
+	public ReactiveSearchHitsImpl(SearchHits<T> delegate) {
+		this.delegate = delegate;
+	}
+
+	@Override
+	public long getTotalHits() {
+		return delegate.getTotalHits();
+	}
+
+	@Override
+	public TotalHitsRelation getTotalHitsRelation() {
+		return delegate.getTotalHitsRelation();
+	}
+
+	@Override
+	public boolean hasAggregations() {
+		return delegate.hasAggregations();
+	}
+
+	@Override
+	@Nullable
+	public AggregationsContainer<?> getAggregations() {
+		return delegate.getAggregations();
+	}
+
+	@Override
+	public float getMaxScore() {
+		return delegate.getMaxScore();
+	}
+
+	@Override
+	public boolean hasSearchHits() {
+		return delegate.hasSearchHits();
+	}
+
+	@Override
+	public Flux<SearchHit<T>> getSearchHits() {
+		return Flux.defer(() -> Flux.fromIterable(delegate.getSearchHits()));
+	}
+
+	@Override
+	@Nullable
+	public Suggest getSuggest() {
+		return delegate.getSuggest();
+	}
+
+	@Override
+	public boolean hasSuggest() {
+		return delegate.hasSuggest();
+	}
+}