DATAES-467 - Fix sorting by _score if Spring Data sort is used.

Original pull request: #209.

Author: xhaggi

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

@@ -67,6 +67,7 @@
 import org.elasticsearch.search.aggregations.AbstractAggregationBuilder;
 import org.elasticsearch.search.fetch.subphase.highlight.HighlightBuilder;
 import org.elasticsearch.search.sort.FieldSortBuilder;
+import org.elasticsearch.search.sort.ScoreSortBuilder;
 import org.elasticsearch.search.sort.SortBuilder;
 import org.elasticsearch.search.sort.SortBuilders;
 import org.elasticsearch.search.sort.SortOrder;
@@ -131,6 +132,8 @@
 public class ElasticsearchTemplate implements ElasticsearchOperations, ApplicationContextAware {
 
 	private static final Logger logger = LoggerFactory.getLogger(ElasticsearchTemplate.class);
+	private static final String FIELD_SCORE = "_score";
+
 	private Client client;
 	private ElasticsearchConverter elasticsearchConverter;
 	private ResultsMapper resultsMapper;
@@ -1022,15 +1025,27 @@ private SearchRequestBuilder prepareSearch(Query query) {
 
 		if (query.getSort() != null) {
 			for (Sort.Order order : query.getSort()) {
-				FieldSortBuilder sort = SortBuilders.fieldSort(order.getProperty())
-						.order(order.getDirection().isDescending() ? SortOrder.DESC : SortOrder.ASC);
-				if (order.getNullHandling() == Sort.NullHandling.NULLS_FIRST) {
-					sort.missing("_first");
-				}
-				else if (order.getNullHandling() == Sort.NullHandling.NULLS_LAST) {
-					sort.missing("_last");
+				SortOrder sortOrder = order.getDirection().isDescending() ? SortOrder.DESC : SortOrder.ASC;
+
+				if (FIELD_SCORE.equals(order.getProperty())) {
+					ScoreSortBuilder sort = SortBuilders //
+							.scoreSort() //
+							.order(sortOrder);
+
+					searchRequestBuilder.addSort(sort);
+				} else {
+					FieldSortBuilder sort = SortBuilders //
+							.fieldSort(order.getProperty()) //
+							.order(sortOrder);
+
+					if (order.getNullHandling() == Sort.NullHandling.NULLS_FIRST) {
+						sort.missing("_first");
+					} else if (order.getNullHandling() == Sort.NullHandling.NULLS_LAST) {
+						sort.missing("_last");
+					}
+
+					searchRequestBuilder.addSort(sort);
 				}
-				searchRequestBuilder.addSort(sort);
 			}
 		}
 

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

@@ -564,6 +564,29 @@ public void shouldSortResultsGivenNullLastSortCriteria() {
 		assertThat(sampleEntities.getContent().get(1).getMessage(), is(sampleEntity2.getMessage()));
 	}
 
+	@Test // DATAES-467
+	public void shouldSortResultsByScore() {
+		// given
+		List<SampleEntity> entities = Arrays.asList( //
+				SampleEntity.builder().id("1").message("abc").build(), //
+				SampleEntity.builder().id("2").message("def").build(), //
+				SampleEntity.builder().id("3").message("ghi").build());
+
+		elasticsearchTemplate.bulkIndex(getIndexQueries(entities));
+		elasticsearchTemplate.refresh(SampleEntity.class);
+
+		SearchQuery searchQuery = new NativeSearchQueryBuilder()
+			.withQuery(matchAllQuery())
+			.withPageable(PageRequest.of(0, 10, Sort.by(Sort.Order.asc("_score"))))
+			.build();
+
+		// when
+		Page<SampleEntity> sampleEntities = elasticsearchTemplate.queryForPage(searchQuery, SampleEntity.class);
+
+		// then
+		assertThat(sampleEntities.getTotalElements(), equalTo(3L));
+	}
+
 	@Test
 	public void shouldExecuteStringQuery() {
 		// given