Polishing.

Introduce EnversRevisionEntityInformation to reflect envers-specific revision information. Refactor DefaultRevisionEntityInformation to enum to keep a singleton around. Refine tests.

See #2850
Original pull request: #4003

spring-data-envers/src/main/java/org/springframework/data/envers/repository/support/DefaultRevisionEntityInformation.java

@@ -24,21 +24,27 @@ import org.springframework.data.repository.history.support.RevisionEntityInforma
  * @author Oliver Gierke
  * @author Chaedong Im
  */
-class DefaultRevisionEntityInformation implements RevisionEntityInformation {
+enum DefaultRevisionEntityInformation implements EnversRevisionEntityInformation {
 
+	INSTANCE;
+
+	@Override
 	public Class<?> getRevisionNumberType() {
 		return Integer.class;
 	}
 
+	@Override
 	public boolean isDefaultRevisionEntity() {
 		return true;
 	}
 
+	@Override
 	public Class<?> getRevisionEntityClass() {
 		return DefaultRevisionEntity.class;
 	}
 
-	public String getRevisionTimestampFieldName() {
+	@Override
+	public String getRevisionTimestampPropertyName() {
 		return "timestamp";
 	}
 }

spring-data-envers/src/main/java/org/springframework/data/envers/repository/support/EnversRevisionEntityInformation.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 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.data.envers.repository.support;
+
+import org.springframework.data.repository.history.support.RevisionEntityInformation;
+
+/**
+ * Envers-specific extension to {@link RevisionEntityInformation}.
+ *
+ * @author Mark Paluch
+ * @since 4.0
+ */
+public interface EnversRevisionEntityInformation extends RevisionEntityInformation {
+
+	/**
+	 * Return the name of the timestamp property (annotated with {@link org.hibernate.envers.RevisionTimestamp}).
+	 *
+	 * @return the name of the timestamp property,
+	 */
+	String getRevisionTimestampPropertyName();
+
+}

spring-data-envers/src/main/java/org/springframework/data/envers/repository/support/EnversRevisionRepositoryFactoryBean.java

@@ -20,8 +20,8 @@ import jakarta.persistence.EntityManager;
 import java.util.Optional;
 
 import org.hibernate.envers.DefaultRevisionEntity;
-
 import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;
 import org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean;
@@ -90,7 +90,7 @@ public class EnversRevisionRepositoryFactoryBean<T extends RevisionRepository<S,
 			this.revisionEntityInformation = Optional.ofNullable(revisionEntityClass) //
 					.filter(it -> !it.equals(DefaultRevisionEntity.class))//
 					.<RevisionEntityInformation> map(ReflectionRevisionEntityInformation::new) //
-					.orElseGet(DefaultRevisionEntityInformation::new);
+					.orElse(DefaultRevisionEntityInformation.INSTANCE);
 		}
 
 		@Override

spring-data-envers/src/main/java/org/springframework/data/envers/repository/support/EnversRevisionRepositoryImpl.java

@@ -218,12 +218,10 @@ public class EnversRevisionRepositoryImpl<T, ID, N extends Number & Comparable<N
 	}
 
 	private String getRevisionTimestampFieldName() {
-		if (revisionEntityInformation instanceof ReflectionRevisionEntityInformation reflection) {
-			return reflection.getRevisionTimestampFieldName();
-		} else if (revisionEntityInformation instanceof DefaultRevisionEntityInformation defaultInfo) {
-			return defaultInfo.getRevisionTimestampFieldName();
+		if (revisionEntityInformation instanceof EnversRevisionEntityInformation reflection) {
+			return reflection.getRevisionTimestampPropertyName();
 		} else {
-			return "timestamp";
+			return DefaultRevisionEntityInformation.INSTANCE.getRevisionTimestampPropertyName();
 		}
 	}
 

spring-data-envers/src/main/java/org/springframework/data/envers/repository/support/ReflectionRevisionEntityInformation.java

@@ -30,7 +30,7 @@ import org.springframework.util.ReflectionUtils;
  * @author Oliver Gierke
  * @author Chaedong Im
  */
-public class ReflectionRevisionEntityInformation implements RevisionEntityInformation {
+public class ReflectionRevisionEntityInformation implements EnversRevisionEntityInformation {
 
 	private final Class<?> revisionEntityClass;
 	private final Class<?> revisionNumberType;
@@ -54,22 +54,25 @@ public class ReflectionRevisionEntityInformation implements RevisionEntityInform
 		this.revisionNumberType = revisionNumberFieldCallback.getRequiredType();
 		this.revisionTimestampFieldName = revisionTimestampFieldCallback.getRequiredField().getName();
 		this.revisionEntityClass = revisionEntityClass;
-
 	}
 
+	@Override
 	public boolean isDefaultRevisionEntity() {
 		return false;
 	}
 
+	@Override
 	public Class<?> getRevisionEntityClass() {
 		return this.revisionEntityClass;
 	}
 
+	@Override
 	public Class<?> getRevisionNumberType() {
 		return this.revisionNumberType;
 	}
 
-	public String getRevisionTimestampFieldName() {
+	@Override
+	public String getRevisionTimestampPropertyName() {
 		return this.revisionTimestampFieldName;
 	}
 }

spring-data-envers/src/test/java/org/springframework/data/envers/repository/support/DefaultRevisionEntityInformationUnitTests.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 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.data.envers.repository.support;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for {@link DefaultRevisionEntityInformation}.
+ *
+ * @author Mark Paluch
+ * @author Chaedong Im
+ */
+class DefaultRevisionEntityInformationUnitTests {
+
+	@Test // GH-2850
+	void defaultRevisionEntityInformationReturnsStandardTimestampFieldName() {
+
+		DefaultRevisionEntityInformation revisionInfo = DefaultRevisionEntityInformation.INSTANCE;
+
+		assertThat(revisionInfo.getRevisionTimestampPropertyName()).isEqualTo("timestamp");
+	}
+
+}

spring-data-envers/src/test/java/org/springframework/data/envers/repository/support/ReflectionRevisionEntityInformationUnitTests.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 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.data.envers.repository.support;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.hibernate.envers.RevisionNumber;
+import org.hibernate.envers.RevisionTimestamp;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.data.envers.sample.CustomRevisionEntity;
+
+/**
+ * Unit tests for {@link ReflectionRevisionEntityInformation}.
+ *
+ * @author Mark Paluch
+ * @author Chaedong Im
+ */
+class ReflectionRevisionEntityInformationUnitTests {
+
+	@Test // GH-2850
+	void reflectionRevisionEntityInformationDetectsStandardTimestampField() {
+
+		ReflectionRevisionEntityInformation revisionInfo = new ReflectionRevisionEntityInformation(
+				CustomRevisionEntity.class);
+
+		assertThat(revisionInfo.getRevisionTimestampPropertyName()).isEqualTo("timestamp");
+	}
+
+	@Test // GH-2850
+	void reflectionRevisionEntityInformationDetectsCustomTimestampField() {
+
+		ReflectionRevisionEntityInformation revisionInfo = new ReflectionRevisionEntityInformation(
+				WithCustomTimestampPropertyName.class);
+
+		assertThat(revisionInfo.getRevisionTimestampPropertyName()).isEqualTo("myCustomTimestamp");
+	}
+
+	/**
+	 * Custom revision entity with a non-standard timestamp field name to test dynamic timestamp property detection.
+	 *
+	 * @author Chaedong Im
+	 */
+	private static class WithCustomTimestampPropertyName {
+
+		@RevisionNumber private int revisionId;
+
+		@RevisionTimestamp private long myCustomTimestamp; // Non-standard field name
+	}
+
+}

spring-data-envers/src/test/java/org/springframework/data/envers/sample/CustomRevisionEntityWithDifferentTimestamp.java

@@ -1,56 +0,0 @@
-/*
- * Copyright 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.data.envers.sample;
-
-import jakarta.persistence.Entity;
-import jakarta.persistence.GeneratedValue;
-import jakarta.persistence.Id;
-
-import org.hibernate.envers.RevisionEntity;
-import org.hibernate.envers.RevisionNumber;
-import org.hibernate.envers.RevisionTimestamp;
-
-/**
- * Custom revision entity with a non-standard timestamp field name to test dynamic timestamp property detection.
- *
- * @author Chaedong Im
- */
-@Entity
-@RevisionEntity
-public class CustomRevisionEntityWithDifferentTimestamp {
-
-	@Id @GeneratedValue @RevisionNumber 
-	private int revisionId;
-	
-	@RevisionTimestamp
-	private long myCustomTimestamp;  // Non-standard field name
-	
-	public int getRevisionId() {
-		return revisionId;
-	}
-	
-	public void setRevisionId(int revisionId) {
-		this.revisionId = revisionId;
-	}
-	
-	public long getMyCustomTimestamp() {
-		return myCustomTimestamp;
-	}
-	
-	public void setMyCustomTimestamp(long myCustomTimestamp) {
-		this.myCustomTimestamp = myCustomTimestamp;
-	}
-}