Polishing.

Reformat code. Make getAnnotatedHint non-nullable.

See #3230
Original pull request: #4339

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/Hint.java

@@ -35,11 +35,17 @@ import org.springframework.core.annotation.AliasFor;
 @Documented
 public @interface Hint {
 
+	/**
+	 * The name of the index to use. In case of an {@literal aggregation} the index is evaluated against the initial
+	 * collection or view.
+	 *
+	 * @return the index name.
+	 */
 	String value() default "";
 
 	/**
 	 * The name of the index to use. In case of an {@literal aggregation} the index is evaluated against the initial
-	 * collection or view. Specify the index either by the index name.
+	 * collection or view.
 	 *
 	 * @return the index name.
 	 */

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractMongoQuery.java

@@ -238,6 +238,7 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		if (!method.hasAnnotatedHint()) {
 			return query;
 		}
+
 		return query.withHint(method.getAnnotatedHint());
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractReactiveMongoQuery.java

@@ -282,6 +282,7 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 		if (!method.hasAnnotatedHint()) {
 			return query;
 		}
+
 		return query.withHint(method.getAnnotatedHint());
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AggregationUtils.java

@@ -114,6 +114,7 @@ abstract class AggregationUtils {
 		if (!queryMethod.hasAnnotatedHint()) {
 			return builder;
 		}
+
 		return builder.hint(queryMethod.getAnnotatedHint());
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/MongoQueryMethod.java

@@ -368,20 +368,19 @@ public class MongoQueryMethod extends QueryMethod {
 	 * @since 4.1
 	 */
 	public boolean hasAnnotatedHint() {
-		return StringUtils.hasText(getAnnotatedHint());
+		return doFindAnnotation(Hint.class).map(Hint::indexName).filter(StringUtils::hasText).isPresent();
 	}
 
 	/**
 	 * Returns the aggregation pipeline declared via a {@link Hint} annotation.
 	 *
-	 * @return the index name (might be empty) or {@literal null} if not present.
+	 * @return the index name (might be empty).
+	 * @throws IllegalStateException if the method is not annotated with {@link Hint}
 	 * @since 4.1
 	 */
-	@Nullable
 	public String getAnnotatedHint() {
-
-		Optional<Hint> hint = doFindAnnotation(Hint.class);
-		return hint.map(Hint::indexName).orElse(null);
+		return doFindAnnotation(Hint.class).map(Hint::indexName).orElseThrow(() -> new IllegalStateException(
+				"Expected to find @Hint annotation but did not; Make sure to check hasAnnotatedHint() before."));
 	}
 
 	private Optional<String[]> findAnnotatedAggregation() {

src/main/asciidoc/reference/mongo-repositories.adoc

@@ -312,8 +312,9 @@ List<Person> findByLastname(String lastname);
 @Query(value = "{ 'firstname' : ?0 }", hint = "firstname-idx") <2>
 List<Person> findByFirstname(String firstname);
 ----
+
 <1> Use the index with name `lastname-idx`.
-<2> The `@Query` annotation defines the `hint` alias which is equivalent to explicitly adding the `@Hint` annotation.
+<2> The `@Query` annotation defines the `hint` alias which is equivalent to adding the `@Hint` annotation.
 ====
 
 [[mongodb.repositories.queries.update]]