GH-2370 - Polishing.

Author: michael-simons

src/main/java/org/springframework/data/neo4j/core/DefaultNeo4jClient.java

@@ -178,6 +178,7 @@ public <T> OngoingDelegation<T> delegateTo(Function<QueryRunner, Optional<T>> ca
 	}
 
 	@Override
+	@Nullable
 	public DatabaseSelectionProvider getDatabaseSelectionProvider() {
 		return databaseSelectionProvider;
 	}

src/main/java/org/springframework/data/neo4j/core/DefaultReactiveNeo4jClient.java

@@ -161,16 +161,12 @@ public RxResult run(Query query) {
 
 	<T> Mono<T> doInQueryRunnerForMono(Mono<DatabaseSelection> databaseSelection, Function<RxQueryRunner, Mono<T>> func) {
 
-		return Mono.usingWhen(getQueryRunner(databaseSelection),
-				func::apply,
-				runner -> ((DelegatingQueryRunner) runner).close());
+		return Mono.usingWhen(getQueryRunner(databaseSelection), func, runner -> ((DelegatingQueryRunner) runner).close());
 	}
 
 	<T> Flux<T> doInStatementRunnerForFlux(Mono<DatabaseSelection> databaseSelection, Function<RxQueryRunner, Flux<T>> func) {
 
-		return Flux.usingWhen(getQueryRunner(databaseSelection),
-				func::apply,
-				runner -> ((DelegatingQueryRunner) runner).close());
+		return Flux.usingWhen(getQueryRunner(databaseSelection), func, runner -> ((DelegatingQueryRunner) runner).close());
 	}
 
 	@Override
@@ -189,6 +185,7 @@ public <T> OngoingDelegation<T> delegateTo(Function<RxQueryRunner, Mono<T>> call
 	}
 
 	@Override
+	@Nullable
 	public ReactiveDatabaseSelectionProvider getDatabaseSelectionProvider() {
 		return databaseSelectionProvider;
 	}

src/main/java/org/springframework/data/neo4j/core/Neo4jClient.java

@@ -109,6 +109,7 @@ default QueryRunner getQueryRunner() {
 	 *
 	 * @return The database selection provider - can be null
 	 */
+	@Nullable
 	DatabaseSelectionProvider getDatabaseSelectionProvider();
 
 	/**

src/main/java/org/springframework/data/neo4j/core/ReactiveNeo4jClient.java

@@ -112,7 +112,9 @@ default Mono<RxQueryRunner> getQueryRunner() {
 	 *
 	 * @return The database selection provider - can be null
 	 */
+	@Nullable
 	ReactiveDatabaseSelectionProvider getDatabaseSelectionProvider();
+
 	/**
 	 * @param <T> The resulting type of this mapping
 	 * @since 6.0