DATAES-952 - Optimize SearchPage implementation.

Original PR: #539

src/main/java/org/springframework/data/elasticsearch/core/SearchHitSupport.java

@@ -158,5 +158,13 @@ public final class SearchHitSupport {
 		public SearchHits<T> getSearchHits() {
 			return searchHits;
 		}
+
+		/*
+		 * return the same instance as in getSearchHits().getSearchHits()
+		 */
+		@Override
+		public List<SearchHit<T>> getContent() {
+			return searchHits.getSearchHits();
+		}
 	}
 }

src/main/java/org/springframework/data/elasticsearch/core/SearchHitsImpl.java

@@ -19,6 +19,7 @@ import java.util.Collections;
 import java.util.List;
 
 import org.elasticsearch.search.aggregations.Aggregations;
+import org.springframework.data.util.Lazy;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -35,9 +36,10 @@ public class SearchHitsImpl<T> implements SearchScrollHits<T> {
 	private final long totalHits;
 	private final TotalHitsRelation totalHitsRelation;
 	private final float maxScore;
-	private final String scrollId;
+	@Nullable private final String scrollId;
 	private final List<? extends SearchHit<T>> searchHits;
-	private final Aggregations aggregations;
+	private final Lazy<List<SearchHit<T>>> unmodifiableSearchHits;
+	@Nullable private final Aggregations aggregations;
 
 	/**
 	 * @param totalHits the number of total hits for the search
@@ -58,6 +60,7 @@ public class SearchHitsImpl<T> implements SearchScrollHits<T> {
 		this.scrollId = scrollId;
 		this.searchHits = searchHits;
 		this.aggregations = aggregations;
+		this.unmodifiableSearchHits = Lazy.of(() -> Collections.unmodifiableList(searchHits));
 	}
 
 	// region getter
@@ -84,7 +87,7 @@ public class SearchHitsImpl<T> implements SearchScrollHits<T> {
 
 	@Override
 	public List<SearchHit<T>> getSearchHits() {
-		return Collections.unmodifiableList(searchHits);
+		return unmodifiableSearchHits.get();
 	}
 	// endregion
 

src/main/java/org/springframework/data/elasticsearch/core/SearchScrollHits.java

@@ -15,12 +15,15 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import org.springframework.lang.Nullable;
+
 /**
  * This interface is used to expose the current {@code scrollId} from the underlying scroll context.
  * <p>
  * Internal use only.
  * 
  * @author Sascha Woo
+ * @author Peter-Josef Meisch
  * @param <T>
  * @since 4.0
  */
@@ -29,6 +32,7 @@ public interface SearchScrollHits<T> extends SearchHits<T> {
 	/**
 	 * @return the scroll id
 	 */
+	@Nullable
 	String getScrollId();
 
 }

src/test/java/org/springframework/data/elasticsearch/core/SearchHitSupportTest.java

@@ -19,17 +19,23 @@ import static java.util.Collections.*;
 import static org.assertj.core.api.Assertions.*;
 import static org.mockito.Mockito.*;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Iterator;
+import java.util.List;
 
 import org.elasticsearch.search.aggregations.Aggregations;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
+import org.springframework.data.domain.PageRequest;
 import org.springframework.data.util.CloseableIterator;
 
 /**
  * @author Roman Puchkovskiy
+ * @author Peter-Josef Meisch
  */
 class SearchHitSupportTest {
+
 	@Test // DATAES-772
 	void unwrapsSearchHitsIteratorToCloseableIteratorOfEntities() {
 		TestStringSearchHitsIterator searchHitsIterator = new TestStringSearchHitsIterator();
@@ -38,6 +44,7 @@ class SearchHitSupportTest {
 		CloseableIterator<String> unwrappedIterator = (CloseableIterator<String>) SearchHitSupport
 				.unwrapSearchHits(searchHitsIterator);
 
+		// noinspection ConstantConditions
 		assertThat(unwrappedIterator.next()).isEqualTo("one");
 		assertThat(unwrappedIterator.next()).isEqualTo("two");
 		assertThat(unwrappedIterator.hasNext()).isFalse();
@@ -47,6 +54,27 @@ class SearchHitSupportTest {
 		assertThat(searchHitsIterator.closed).isTrue();
 	}
 
+	@Test // DATAES-952
+	@DisplayName("should return the same list instance in SearchHits and getContent")
+	void shouldReturnTheSameListInstanceInSearchHitsAndGetContent() {
+
+		List<SearchHit<String>> hits = new ArrayList<>();
+		hits.add(new SearchHit<>(null, null, 0, null, null, "one"));
+		hits.add(new SearchHit<>(null, null, 0, null, null, "two"));
+		hits.add(new SearchHit<>(null, null, 0, null, null, "three"));
+		hits.add(new SearchHit<>(null, null, 0, null, null, "four"));
+		hits.add(new SearchHit<>(null, null, 0, null, null, "five"));
+
+		SearchHits<String> originalSearchHits = new SearchHitsImpl<>(hits.size(), TotalHitsRelation.EQUAL_TO, 0, "scroll",
+				hits, null);
+
+		SearchPage<String> searchPage = SearchHitSupport.searchPageFor(originalSearchHits, PageRequest.of(0, 3));
+		SearchHits<String> searchHits = searchPage.getSearchHits();
+
+		assertThat(searchHits).isEqualTo(originalSearchHits);
+		assertThat(searchHits.getSearchHits()).isSameAs(searchPage.getContent());
+	}
+
 	private static class TestStringSearchHitsIterator implements SearchHitsIterator<String> {
 		private final Iterator<String> iterator = Arrays.asList("one", "two").iterator();
 		private boolean closed = false;
@@ -87,4 +115,5 @@ class SearchHitSupportTest {
 			return new SearchHit<>("index", "id", 1.0f, new Object[0], emptyMap(), nextString);
 		}
 	}
+
 }