Use ConcurrentHashMap in InMemoryReactiveClientRegistrationRepository

Fixes spring-projectsgh-7299

Author: eberttc

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/registration/InMemoryReactiveClientRegistrationRepository.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,18 +18,19 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import org.springframework.util.Assert;
-import org.springframework.util.ConcurrentReferenceHashMap;
 
 import reactor.core.publisher.Mono;
 
 /**
  * A Reactive {@link ClientRegistrationRepository} that stores {@link ClientRegistration}(s) in-memory.
  *
  * @author Rob Winch
+ * @author Ebert Toribio
  * @since 5.1
  * @see ClientRegistrationRepository
  * @see ClientRegistration
@@ -46,7 +47,7 @@ public final class InMemoryReactiveClientRegistrationRepository
 	 */
 	public InMemoryReactiveClientRegistrationRepository(ClientRegistration... registrations) {
 		Assert.notEmpty(registrations, "registrations cannot be empty");
-		this.clientIdToClientRegistration = new ConcurrentReferenceHashMap<>();
+		this.clientIdToClientRegistration = new ConcurrentHashMap<>();
 		for (ClientRegistration registration : registrations) {
 			Assert.notNull(registration, "registrations cannot contain null values");
 			this.clientIdToClientRegistration.put(registration.getRegistrationId(), registration);