DATAES-754 - Completion field deserialization is failing due to class cast error.

Original PR: spring-projects#399

Author: sothawo

src/main/java/org/springframework/data/elasticsearch/core/completion/Completion.java

@@ -3,6 +3,7 @@
 import java.util.List;
 import java.util.Map;
 
+import org.springframework.data.annotation.PersistenceConstructor;
 import org.springframework.lang.Nullable;
 
 /**
@@ -23,6 +24,11 @@ public Completion(String[] input) {
 		this.input = input;
 	}
 
+	@PersistenceConstructor
+	public Completion(List<String> input) {
+		this.input = input.toArray(new String[0]);
+	}
+
 	public String[] getInput() {
 		return input;
 	}

src/test/java/org/springframework/data/elasticsearch/core/completion/ElasticsearchTemplateCompletionTests.java

@@ -87,7 +87,8 @@ private void loadCompletionObjectEntities() {
 		indexQueries.add(new CompletionEntityBuilder("4").name("Artur Konczak").suggest(new String[] { "Artur", "Konczak" })
 				.buildIndex());
 
-		operations.bulkIndex(indexQueries, IndexCoordinates.of("test-index-core-completion").withTypes("completion-type"));
+		IndexCoordinates index = IndexCoordinates.of("test-index-core-completion");
+		operations.bulkIndex(indexQueries, index);
 		operations.indexOps(CompletionEntity.class).refresh();
 	}
 
@@ -151,6 +152,13 @@ public void shouldFindSuggestionsForGivenCriteriaQueryUsingCompletionEntity() {
 		assertThat(options.get(1).getText().string()).isIn("Marchand", "Mohsin");
 	}
 
+	@Test // DATAES-754
+	void shouldRetrieveEntityWithCompletion() {
+		loadCompletionObjectEntities();
+		IndexCoordinates index = IndexCoordinates.of("test-index-core-completion");
+		operations.get("1", CompletionEntity.class, index);
+	}
+
 	@Test
 	public void shouldFindSuggestionsForGivenCriteriaQueryUsingAnnotatedCompletionEntity() {