DATACMNS-1231 - Introduce dedicated Auditor value object.

Original Pull Request: #458

Author: christophstrobl

src/main/java/org/springframework/data/auditing/AuditingHandler.java

@@ -19,7 +19,6 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.data.domain.AuditorAware;
 import org.springframework.data.mapping.PersistentEntity;
@@ -90,7 +89,7 @@ public <T> T markCreated(T source) {
 
 		Assert.notNull(source, "Entity must not be null!");
 
-		return markCreated(auditorAware.flatMap(AuditorAware::getCurrentAuditor).orElse(null), source);
+		return markCreated(getAuditor(), source);
 	}
 
 	/**
@@ -102,7 +101,13 @@ public <T> T markModified(T source) {
 
 		Assert.notNull(source, "Entity must not be null!");
 
-		return markModified(auditorAware.flatMap(AuditorAware::getCurrentAuditor).orElse(null), source);
+		return markModified(getAuditor(), source);
+	}
+
+	Auditor<?> getAuditor() {
+
+		return auditorAware.map(AuditorAware::getCurrentAuditor).map(Auditor::ofOptional) //
+				.orElse(Auditor.none());
 	}
 
 	/*
@@ -111,8 +116,6 @@ public <T> T markModified(T source) {
 	 */
 	public void afterPropertiesSet() {
 
-		super.afterPropertiesSet();
-
 		if (!auditorAware.isPresent()) {
 			logger.debug("No AuditorAware set! Auditing will not be applied!");
 		}

src/main/java/org/springframework/data/auditing/AuditingHandlerSupport.java

@@ -21,7 +21,6 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
-import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.log.LogMessage;
 import org.springframework.data.domain.Auditable;
 import org.springframework.data.mapping.context.PersistentEntities;
@@ -36,11 +35,11 @@
  * @author Mark Paluch
  * @since 2.4
  */
-public abstract class AuditingHandlerSupport implements InitializingBean {
+public abstract class AuditingHandlerSupport {
 
 	private static final Log logger = LogFactory.getLog(AuditingHandlerSupport.class);
 
-	private final DefaultAuditableBeanWrapperFactory factory;
+	private final AuditableBeanWrapperFactory factory;
 
 	private DateTimeProvider dateTimeProvider = CurrentDateTimeProvider.INSTANCE;
 	private boolean dateTimeForNow = true;
@@ -83,40 +82,34 @@ public void setModifyOnCreation(boolean modifyOnCreation) {
 	/**
 	 * Sets the {@link DateTimeProvider} to be used to determine the dates to be set.
 	 *
-	 * @param dateTimeProvider
+	 * @param dateTimeProvider can be {@literal null}, defaults to {@link CurrentDateTimeProvider} in that case.
 	 */
 	public void setDateTimeProvider(@Nullable DateTimeProvider dateTimeProvider) {
 		this.dateTimeProvider = dateTimeProvider == null ? CurrentDateTimeProvider.INSTANCE : dateTimeProvider;
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
-	 */
-	public void afterPropertiesSet() {}
-
 	/**
-	 * Returns whether the given source is considered to be auditable in the first place
+	 * Returns whether the given source is considered to be auditable in the first place.
 	 *
 	 * @param source must not be {@literal null}.
-	 * @return
+	 * @return {@literal true} if the given {@literal source} considered to be auditable.
 	 */
 	protected final boolean isAuditable(Object source) {
 
-		Assert.notNull(source, "Source must not be null!");
+		Assert.notNull(source, "Source entity must not be null!");
 
 		return factory.getBeanWrapperFor(source).isPresent();
 	}
 
 	/**
 	 * Marks the given object as created.
 	 *
-	 * @param auditor
-	 * @param source
+	 * @param auditor can be {@literal null}.
+	 * @param source must not be {@literal null}.
 	 */
-	<T> T markCreated(@Nullable Object auditor, T source) {
+	<T> T markCreated(Auditor auditor, T source) {
 
-		Assert.notNull(source, "Entity must not be null!");
+		Assert.notNull(source, "Source entity must not be null!");
 
 		return touch(auditor, source, true);
 	}
@@ -127,28 +120,26 @@ <T> T markCreated(@Nullable Object auditor, T source) {
 	 * @param auditor
 	 * @param source
 	 */
-	<T> T markModified(@Nullable Object auditor, T source) {
+	<T> T markModified(Auditor auditor, T source) {
 
-		Assert.notNull(source, "Entity must not be null!");
+		Assert.notNull(source, "Source entity must not be null!");
 
 		return touch(auditor, source, false);
 	}
 
-	private <T> T touch(@Nullable Object auditor, T target, boolean isNew) {
+	private <T> T touch(Auditor auditor, T target, boolean isNew) {
 
 		Optional<AuditableBeanWrapper<T>> wrapper = factory.getBeanWrapperFor(target);
 
 		return wrapper.map(it -> {
 
-			if (auditor != null) {
-				touchAuditor(auditor, it, isNew);
-			}
+			touchAuditor(auditor, it, isNew);
 			Optional<TemporalAccessor> now = dateTimeForNow ? touchDate(it, isNew) : Optional.empty();
 
 			if (logger.isDebugEnabled()) {
 
 				Object defaultedNow = now.map(Object::toString).orElse("not set");
-				Object defaultedAuditor = auditor != null ? auditor.toString() : "unknown";
+				Object defaultedAuditor = auditor.isPresent() ? auditor.toString() : "unknown";
 
 				logger.debug(
 						LogMessage.format("Touched %s - Last modification at %s by %s", target, defaultedNow, defaultedAuditor));
@@ -166,17 +157,20 @@ private <T> T touch(@Nullable Object auditor, T target, boolean isNew) {
 	 * @param isNew
 	 * @return
 	 */
-	private void touchAuditor(Object auditor, AuditableBeanWrapper<?> wrapper, boolean isNew) {
+	private void touchAuditor(Auditor auditor, AuditableBeanWrapper<?> wrapper, boolean isNew) {
+
+		if(!auditor.isPresent()) {
+			return;
+		}
 
 		Assert.notNull(wrapper, "AuditableBeanWrapper must not be null!");
-		Assert.notNull(auditor, "Auditor must not be null!");
 
 		if (isNew) {
-			wrapper.setCreatedBy(auditor);
+			wrapper.setCreatedBy(auditor.getValue());
 		}
 
 		if (!isNew || modifyOnCreation) {
-			wrapper.setLastModifiedBy(auditor);
+			wrapper.setLastModifiedBy(auditor.getValue());
 		}
 	}
 

src/main/java/org/springframework/data/auditing/Auditor.java

@@ -0,0 +1,122 @@
+/*
+ * 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.data.auditing;
+
+import java.util.Optional;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * Value Object encapsulating the actual auditor value.
+ *
+ * @author Christoph Strobl
+ * @since 2.4
+ */
+class Auditor<T> {
+
+	private static final Auditor NONE = new Auditor(null) {
+
+		@Override
+		public boolean isPresent() {
+			return false;
+		}
+	};
+
+	private final @Nullable T value;
+
+	private Auditor(@Nullable T value) {
+		this.value = value;
+	}
+
+	/**
+	 * @return
+	 */
+	@Nullable
+	public T getValue() {
+		return value;
+	}
+
+	/**
+	 * Create an {@link Auditor} for the given {@literal source} value. <br />
+	 * If the given {@literal source} is {@literal null} {@link Auditor#none()} is returned. A source that already is an
+	 * {@link Auditor} gets returned as is.
+	 * 
+	 * @param source can be {@literal null}.
+	 * @param <T>
+	 * @return {@link Auditor#none()} if the given {@literal source} is {@literal null}. }
+	 */
+	public static <T> Auditor<T> of(@Nullable T source) {
+
+		if (source instanceof Auditor) {
+			return (Auditor) source;
+		}
+
+		return source == null ? Auditor.none() : new Auditor<>(source);
+	}
+
+	/**
+	 * Create an {@link Auditor} for the given {@link Optional} value. <br />
+	 * If the given {@literal source} is {@link Optional#empty()} {@link Auditor#none()} is returned. An {@link Optional}
+	 * wrapping and {@link Auditor} returns the unwrapped {@link Auditor} instance as is.
+	 *
+	 * @param source must not be {@literal null}.
+	 * @param <T>
+	 * @return {@link Auditor#none()} if the given {@literal source} is {@literal null}. }
+	 */
+	public static <T> Auditor<T> ofOptional(@Nullable Optional<T> source) {
+		return Auditor.of(source.orElse(null));
+	}
+
+	/**
+	 * Return an {@link Auditor} that is not present.
+	 *
+	 * @param <T>
+	 * @return never {@literal null}.
+	 */
+	public static <T> Auditor<T> none() {
+		return NONE;
+	}
+
+	/**
+	 * @return {@literal true} if {@link #getValue()} returns a non {@literal null} value.
+	 */
+	public boolean isPresent() {
+		return getValue() != null;
+	}
+
+	@Override
+	public String toString() {
+		return value != null ? value.toString() : "Auditor.none()";
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		Auditor<?> auditor = (Auditor<?>) o;
+
+		return ObjectUtils.nullSafeEquals(value, auditor.value);
+	}
+
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHashCode(value);
+	}
+}

src/main/java/org/springframework/data/auditing/ReactiveAuditingHandler.java

@@ -17,8 +17,6 @@
 
 import reactor.core.publisher.Mono;
 
-import java.util.Optional;
-
 import org.springframework.data.domain.ReactiveAuditorAware;
 import org.springframework.data.mapping.context.PersistentEntities;
 import org.springframework.util.Assert;
@@ -27,15 +25,16 @@
  * Auditing handler to mark entity objects created and modified.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 2.4
  */
 public class ReactiveAuditingHandler extends AuditingHandlerSupport {
 
 	private ReactiveAuditorAware<?> auditorAware = Mono::empty;
 
 	/**
-	 * Creates a new {@link AuditableBeanWrapper} using the given {@link PersistentEntities} when looking up auditing
-	 * metadata via reflection.
+	 * Creates a new {@link ReactiveAuditingHandler} using the given {@link PersistentEntities} when looking up auditing
+	 * metadata.
 	 *
 	 * @param entities must not be {@literal null}.
 	 */
@@ -63,9 +62,8 @@ public <T> Mono<T> markCreated(T source) {
 
 		Assert.notNull(source, "Entity must not be null!");
 
-		return auditorAware.getCurrentAuditor().map(Optional::of) //
-				.defaultIfEmpty(Optional.empty()) //
-				.map(auditor -> markCreated(auditor.orElse(null), source));
+		return getAuditor() //
+				.map(auditor -> markCreated(auditor, source));
 	}
 
 	/**
@@ -77,8 +75,14 @@ public <T> Mono<T> markModified(T source) {
 
 		Assert.notNull(source, "Entity must not be null!");
 
-		return auditorAware.getCurrentAuditor().map(Optional::of) //
-				.defaultIfEmpty(Optional.empty()) //
-				.map(auditor -> markModified(auditor.orElse(null), source));
+		return getAuditor() //
+				.map(auditor -> markModified(auditor, source));
+	}
+
+	private Mono<? extends Auditor<?>> getAuditor() {
+
+		return auditorAware.getCurrentAuditor() //
+				.map(Auditor::of) //
+				.defaultIfEmpty(Auditor.none());
 	}
 }

src/main/java/org/springframework/data/domain/ReactiveAuditorAware.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2020 the original author or authors.
+ * 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.
@@ -27,9 +27,10 @@
 public interface ReactiveAuditorAware<T> {
 
 	/**
-	 * Returns the current auditor of the application.
+	 * Returns a {@link Mono} publishing the current auditor of the application.
 	 *
-	 * @return the current auditor. If the mono does not emit a value, the auditor is considered to be unknown.
+	 * @return the {@link Mono} emitting the current auditor, or an empty one, if the auditor is considered to be unknown.
 	 */
 	Mono<T> getCurrentAuditor();
+
 }