DATACMNS-1231 - Add reactive auditing infrastructure.

We now provide a reactive variant for auditing with ReactiveAuditingHandler and ReactiveIsNewAwareAuditingHandler.

Extracted common auditing functionality into AuditingHandlerSupport which serves as base class for AuditingHandler and ReactiveAuditingHandler.

Original Pull Request: #458

src/test/java/org/springframework/data/auditing/ReactiveAuditingHandlerUnitTests.java

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+/*
+ * Copyright 2008-2020 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.data.auditing;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
+import lombok.Value;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import java.time.Instant;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.data.annotation.CreatedBy;
+import org.springframework.data.annotation.CreatedDate;
+import org.springframework.data.annotation.LastModifiedBy;
+import org.springframework.data.annotation.LastModifiedDate;
+import org.springframework.data.domain.ReactiveAuditorAware;
+import org.springframework.data.mapping.context.PersistentEntities;
+import org.springframework.data.mapping.context.SampleMappingContext;
+
+/**
+ * Unit test for {@link ReactiveAuditingHandler}.
+ *
+ * @author Mark Paluch
+ */
+@SuppressWarnings("unchecked")
+class ReactiveAuditingHandlerUnitTests {
+
+	ReactiveAuditingHandler handler;
+	ReactiveAuditorAware<AuditedUser> auditorAware;
+
+	AuditedUser user;
+
+	@BeforeEach
+	void setUp() {
+
+		SampleMappingContext sampleMappingContext = new SampleMappingContext();
+		sampleMappingContext.getRequiredPersistentEntity(Immutable.class); // initialize to ensure we're using mapping
+		// metadata instead of plain reflection
+
+		handler = new ReactiveAuditingHandler(PersistentEntities.of(sampleMappingContext));
+		user = new AuditedUser();
+
+		auditorAware = mock(ReactiveAuditorAware.class);
+		when(auditorAware.getCurrentAuditor()).thenReturn(Mono.just(user));
+	}
+
+	@Test
+	void markCreatedShouldSetDatesIfAuditorNotSet() {
+
+		Immutable immutable = new Immutable(null, null, null, null);
+
+		handler.markCreated(immutable).as(StepVerifier::create).consumeNextWith(actual -> {
+
+			assertThat(actual.getCreatedDate()).isNotNull();
+			assertThat(actual.getModifiedDate()).isNotNull();
+
+			assertThat(actual.getCreatedBy()).isNull();
+			assertThat(actual.getModifiedBy()).isNull();
+		}).verifyComplete();
+
+		assertThat(immutable.getCreatedDate()).isNull();
+	}
+
+	@Test
+	void markModifiedSetsModifiedFields() {
+
+		AuditedUser audited = new AuditedUser();
+		audited.id = 1L;
+
+		handler.setAuditorAware(auditorAware);
+		handler.markModified(audited).as(StepVerifier::create).expectNext(audited).verifyComplete();
+
+		assertThat(audited.getCreatedBy()).isNotPresent();
+		assertThat(audited.getCreatedDate()).isNotPresent();
+
+		assertThat(audited.getLastModifiedBy()).isPresent();
+		assertThat(audited.getLastModifiedDate()).isPresent();
+
+		verify(auditorAware).getCurrentAuditor();
+	}
+
+	@Value
+	static class Immutable {
+
+		@CreatedDate Instant createdDate;
+		@CreatedBy String createdBy;
+		@LastModifiedDate Instant modifiedDate;
+		@LastModifiedBy String modifiedBy;
+	}
+}