Add support for Client Registration Model and InMemory Client Repository

Fixes spring-projectsgh-40

Author: anoopgarlapati

core/src/main/java/org/springframework/security/oauth2/server/authorization/client/InMemoryRegisteredClientRepository.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2020 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.security.oauth2.server.authorization.client;
+
+import org.springframework.util.Assert;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * A {@link RegisteredClientRepository} that stores {@link RegisteredClient}(s) in-memory.
+ *
+ * @author Anoop Garlapati
+ * @since 5.3
+ * @see RegisteredClientRepository
+ * @see RegisteredClient
+ */
+public final class InMemoryRegisteredClientRepository implements RegisteredClientRepository {
+	private final Map<String, RegisteredClient> idRegistrationMap;
+	private final Map<String, RegisteredClient> clientIdRegistrationMap;
+
+	/**
+	 * Constructs an {@code InMemoryRegisteredClientRepository} using the provided parameters.
+	 *
+	 * @param registrations the client registration(s)
+	 */
+	public InMemoryRegisteredClientRepository(RegisteredClient... registrations) {
+		this(Arrays.asList(registrations));
+	}
+
+	/**
+	 * Constructs an {@code InMemoryRegisteredClientRepository} using the provided parameters.
+	 *
+	 * @param registrations the client registration(s)
+	 */
+	public InMemoryRegisteredClientRepository(List<RegisteredClient> registrations) {
+		Assert.notEmpty(registrations, "registrations cannot be empty");
+		ConcurrentHashMap<String, RegisteredClient> idRegistrationMapResult = new ConcurrentHashMap<>();
+		ConcurrentHashMap<String, RegisteredClient> clientIdRegistrationMapResult = new ConcurrentHashMap<>();
+		for (RegisteredClient registration : registrations) {
+			String id = registration.getId();
+			if (idRegistrationMapResult.containsKey(id)) {
+				throw new IllegalArgumentException("Registered client must be unique. " +
+						"Found duplicate identifier: " + id);
+			}
+			String clientId = registration.getClientId();
+			if (clientIdRegistrationMapResult.containsKey(clientId)) {
+				throw new IllegalArgumentException("Registered client must be unique. " +
+						"Found duplicate client identifier: " + clientId);
+			}
+			idRegistrationMapResult.put(id, registration);
+			clientIdRegistrationMapResult.put(clientId, registration);
+		}
+		idRegistrationMap = idRegistrationMapResult;
+		clientIdRegistrationMap = clientIdRegistrationMapResult;
+	}
+
+	@Override
+	public RegisteredClient findById(String id) {
+		Assert.hasText(id, "id cannot be empty");
+		return this.idRegistrationMap.get(id);
+	}
+
+	@Override
+	public RegisteredClient findByClientId(String clientId) {
+		Assert.hasText(clientId, "clientId cannot be empty");
+		return this.clientIdRegistrationMap.get(clientId);
+	}
+}