DATACMNS-1173 - Fixed value lookup of AnnotationRevisionMetadata.

Fixed handling of absent values. Minor refactorings. More unit tests.

src/main/java/org/springframework/data/history/AnnotationRevisionMetadata.java

@@ -85,9 +85,9 @@ public class AnnotationRevisionMetadata<N extends Number & Comparable<N>> implem
 
 		return Lazy.of(() -> {
 
-			AnnotationDetectionFieldCallback numberCallback = new AnnotationDetectionFieldCallback(annotationType);
+			AnnotationDetectionFieldCallback callback = new AnnotationDetectionFieldCallback(annotationType);
-			ReflectionUtils.doWithFields(entity.getClass(), numberCallback);
+			ReflectionUtils.doWithFields(entity.getClass(), callback);
-			return numberCallback.getValue(entity);
+			return Optional.ofNullable(callback.getValue(entity));
 		});
 	}
 }

src/main/java/org/springframework/data/history/RevisionMetadata.java

@@ -40,8 +40,8 @@ public interface RevisionMetadata<N extends Number & Comparable<N>> {
 	 * @throws IllegalStateException if no revision number is available.
 	 */
 	default N getRequiredRevisionNumber() {
-		return getRevisionNumber()
+		return getRevisionNumber().orElseThrow(
-				.orElseThrow(() -> new IllegalStateException(String.format("No revision number found on %s!", getDelegate())));
+				() -> new IllegalStateException(String.format("No revision number found on %s!", (Object) getDelegate())));
 	}
 
 	/**
@@ -58,8 +58,8 @@ public interface RevisionMetadata<N extends Number & Comparable<N>> {
 	 * @throw IllegalStateException if no revision date is available.
 	 */
 	default LocalDateTime getRequiredRevisionDate() {
-		return getRevisionDate()
+		return getRevisionDate().orElseThrow(
-				.orElseThrow(() -> new IllegalStateException(String.format("No revision date found on %s!", getDelegate())));
+				() -> new IllegalStateException(String.format("No revision date found on %s!", (Object) getDelegate())));
 	}
 
 	/**

src/test/java/org/springframework/data/history/AnnotationRevisionMetadataUnitTests.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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.history;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDateTime;
+
+import org.junit.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.annotation.Reference;
+
+/**
+ * Unit tests for {@link AnnotationRevisionMetadata}.
+ * 
+ * @author Oliver Gierke
+ */
+public class AnnotationRevisionMetadataUnitTests {
+
+	@Test // DATACMNS-1173
+	public void exposesNoInformationOnEmptyProbe() {
+
+		Sample sample = new Sample();
+		RevisionMetadata<Long> metadata = getMetadata(sample);
+
+		assertThat(metadata.getRevisionNumber()).isEmpty();
+		assertThat(metadata.getRevisionDate()).isEmpty();
+
+		assertThatExceptionOfType(IllegalStateException.class) //
+				.isThrownBy(() -> metadata.getRequiredRevisionNumber());
+
+		assertThatExceptionOfType(IllegalStateException.class) //
+				.isThrownBy(() -> metadata.getRequiredRevisionDate());
+	}
+
+	@Test // DATACMNS-1173
+	public void exposesRevisionNumber() {
+
+		Sample sample = new Sample();
+		sample.revisionNumber = 1L;
+
+		RevisionMetadata<Long> metadata = getMetadata(sample);
+
+		assertThat(metadata.getRevisionNumber()).hasValue(1L);
+		assertThat(metadata.getRequiredRevisionNumber()).isEqualTo(1L);
+	}
+
+	@Test // DATACMNS-1173
+	public void exposesRevisionDate() {
+
+		Sample sample = new Sample();
+		sample.revisionDate = LocalDateTime.now();
+
+		RevisionMetadata<Long> metadata = getMetadata(sample);
+
+		assertThat(metadata.getRevisionDate()).hasValue(sample.revisionDate);
+		assertThat(metadata.getRequiredRevisionDate()).isEqualTo(sample.revisionDate);
+	}
+
+	private static RevisionMetadata<Long> getMetadata(Sample sample) {
+		return new AnnotationRevisionMetadata<>(sample, Autowired.class, Reference.class);
+	}
+
+	static class Sample {
+
+		@Autowired Long revisionNumber;
+		@Reference LocalDateTime revisionDate;
+	}
+}