GH-2169 - Remove blocking call from ReactiveNeo4jTemplate.

Closes GH-2169

Author: meistermeier

src/main/java/org/springframework/data/neo4j/core/ReactiveNeo4jTemplate.java

@@ -730,7 +730,7 @@ private Mono<DatabaseSelection> getDatabaseName() {
 	@Override
 	public <T> Mono<ExecutableQuery<T>> toExecutableQuery(PreparedQuery<T> preparedQuery) {
 
-		return getDatabaseName().map(databaseName -> {
+		return getDatabaseName().flatMap(databaseName -> {
 			Class<T> resultType = preparedQuery.getResultType();
 			QueryFragmentsAndParameters queryFragmentsAndParameters = preparedQuery.getQueryFragmentsAndParameters();
 			String cypherQuery = queryFragmentsAndParameters.getCypherQuery();
@@ -745,14 +745,19 @@ public <T> Mono<ExecutableQuery<T>> toExecutableQuery(PreparedQuery<T> preparedQ
 				Map<String, Object> parameters = queryFragmentsAndParameters.getParameters();
 
 				if (containsPossibleCircles && !queryFragments.isScalarValueReturn()) {
-					GenericQueryAndParameters genericQueryAndParameters =
-							createQueryAndParameters(entityMetaData, queryFragments, parameters).block();
+					return createQueryAndParameters(entityMetaData, queryFragments, parameters)
+							.map(genericQueryAndParameters -> {
+								ReactiveNeo4jClient.MappingSpec<T> mappingSpec = this.neo4jClient.query(renderer.render(GenericQueryAndParameters.STATEMENT))
+										.in(databaseName.getValue()).bindAll(genericQueryAndParameters.getParameters()).fetchAs(resultType);
 
-					cypherQuery = renderer.render(GenericQueryAndParameters.STATEMENT);
-					finalParameters = genericQueryAndParameters.getParameters();
-				} else {
-					cypherQuery = renderer.render(queryFragments.toStatement());
+								ReactiveNeo4jClient.RecordFetchSpec<T> fetchSpec = preparedQuery.getOptionalMappingFunction()
+										.map(mappingFunction -> mappingSpec.mappedBy(mappingFunction)).orElse(mappingSpec);
+
+								return new DefaultReactiveExecutableQuery<>(preparedQuery, fetchSpec);
+							});
 				}
+
+				cypherQuery = renderer.render(queryFragments.toStatement());
 			}
 
 			ReactiveNeo4jClient.MappingSpec<T> mappingSpec = this.neo4jClient.query(cypherQuery)
@@ -761,7 +766,7 @@ public <T> Mono<ExecutableQuery<T>> toExecutableQuery(PreparedQuery<T> preparedQ
 			ReactiveNeo4jClient.RecordFetchSpec<T> fetchSpec = preparedQuery.getOptionalMappingFunction()
 					.map(mappingFunction -> mappingSpec.mappedBy(mappingFunction)).orElse(mappingSpec);
 
-			return new DefaultReactiveExecutableQuery<>(preparedQuery, fetchSpec);
+			return Mono.just(new DefaultReactiveExecutableQuery<>(preparedQuery, fetchSpec));
 		});
 	}