Add Support SupplierReactiveClientRegistrationRepository

Closes spring-projectsgh-16750

Signed-off-by: Max Batischev <[email protected]>

Author: franticticktick

Diff for: oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/registration/SupplierReactiveClientRegistrationRepository.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2002-2025 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.client.registration;
+
+import java.util.Iterator;
+import java.util.function.Supplier;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.util.Assert;
+import org.springframework.util.function.SingletonSupplier;
+
+/**
+ * A {@link ReactiveClientRegistrationRepository} that lazily calls to retrieve
+ * {@link ClientRegistration}(s) when requested.
+ *
+ * @author Max Batischev
+ * @since 6.5
+ * @see ReactiveClientRegistrationRepository
+ * @see ClientRegistration
+ */
+public final class SupplierReactiveClientRegistrationRepository
+		implements ReactiveClientRegistrationRepository, Iterable<ClientRegistration> {
+
+	private final Supplier<? extends ReactiveClientRegistrationRepository> repositorySupplier;
+
+	/**
+	 * Constructs an {@code SupplierReactiveClientRegistrationRepository} using the
+	 * provided parameters.
+	 * @param repositorySupplier the client registration repository supplier
+	 */
+	public <T extends ReactiveClientRegistrationRepository & Iterable<ClientRegistration>> SupplierReactiveClientRegistrationRepository(
+			Supplier<? extends ReactiveClientRegistrationRepository> repositorySupplier) {
+		Assert.notNull(repositorySupplier, "repositorySupplier cannot be null");
+		this.repositorySupplier = SingletonSupplier.of(repositorySupplier);
+	}
+
+	@Override
+	public Mono<ClientRegistration> findByRegistrationId(String registrationId) {
+		Assert.hasText(registrationId, "registrationId cannot be empty");
+		return this.repositorySupplier.get().findByRegistrationId(registrationId);
+	}
+
+	/**
+	 * Returns an {@code Iterator} of {@link ClientRegistration}.
+	 * @return an {@code Iterator<ClientRegistration>}
+	 */
+	@Override
+	public Iterator<ClientRegistration> iterator() {
+		return ((Iterable<ClientRegistration>) this.repositorySupplier.get()).iterator();
+	}
+
+}

Diff for: oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/registration/SupplierReactiveClientRegistrationRepositoryTests.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2002-2025 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.client.registration;
+
+import java.util.function.Supplier;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Tests for {@link SupplierReactiveClientRegistrationRepository}.
+ *
+ * @author Max Batischev
+ */
+@ExtendWith(MockitoExtension.class)
+public class SupplierReactiveClientRegistrationRepositoryTests {
+
+	private final ClientRegistration registration = TestClientRegistrations.clientRegistration().build();
+
+	private final SupplierReactiveClientRegistrationRepository registrationRepository = new SupplierReactiveClientRegistrationRepository(
+			() -> new InMemoryReactiveClientRegistrationRepository(this.registration));
+
+	@Mock
+	private Supplier<InMemoryReactiveClientRegistrationRepository> clientRegistrationRepositorySupplier;
+
+	@Test
+	void constructWhenNullThenIllegalArgumentException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> new SupplierReactiveClientRegistrationRepository(null));
+	}
+
+	@Test
+	public void findRegistrationWhenRegistrationIsPresentThenReturns() {
+		String id = this.registration.getRegistrationId();
+		assertThat(this.registrationRepository.findByRegistrationId(id).block()).isEqualTo(this.registration);
+	}
+
+	@Test
+	public void findRegistrationWhenRegistrationIsNotPresentThenNull() {
+		String id = this.registration.getRegistrationId() + "MISSING";
+		assertThat(this.registrationRepository.findByRegistrationId(id).block()).isNull();
+	}
+
+	@Test
+	public void findRegistrationWhenNullIdIsPresentThenThrowsException() {
+		assertThatIllegalArgumentException()
+			.isThrownBy(() -> this.registrationRepository.findByRegistrationId(null).block());
+	}
+
+	@Test
+	public void findRegistrationWhenIdIsPresentThenSingletonSupplierCached() {
+		given(this.clientRegistrationRepositorySupplier.get())
+			.willReturn(new InMemoryReactiveClientRegistrationRepository(this.registration));
+		SupplierReactiveClientRegistrationRepository test = new SupplierReactiveClientRegistrationRepository(
+				this.clientRegistrationRepositorySupplier);
+
+		String id = this.registration.getRegistrationId();
+		assertThat(test.findByRegistrationId(id).block()).isEqualTo(this.registration);
+
+		id = this.registration.getRegistrationId();
+		assertThat(test.findByRegistrationId(id).block()).isEqualTo(this.registration);
+		verify(this.clientRegistrationRepositorySupplier, times(1)).get();
+	}
+
+	@Test
+	public void iteratorWhenRemoveThenThrowsUnsupportedOperationException() {
+		assertThatExceptionOfType(UnsupportedOperationException.class)
+			.isThrownBy(this.registrationRepository.iterator()::remove);
+	}
+
+	@Test
+	public void iteratorWhenGetThenContainsAll() {
+		assertThat(this.registrationRepository).containsOnly(this.registration);
+	}
+
+}