DATACMNS-1779 - Consider kotlin.Unit a simple type.

kotlin.Unit is now considered a simple type to avoid PersistentEntity creation.

ReflectionUtils.isVoid(…) now encapsulates the check so that calling code doesn't need to check if Kotlin is on the class path.

src/main/java/org/springframework/data/mapping/model/SimpleTypeHolder.java

@@ -157,7 +157,7 @@ public class SimpleTypeHolder {
 
 		String typeName = type.getName();
 
-		if (typeName.startsWith("java.lang") || type.getName().startsWith("java.time")) {
+		if (typeName.startsWith("java.lang") || type.getName().startsWith("java.time") || typeName.equals("kotlin.Unit")) {
 			return true;
 		}
 

src/main/java/org/springframework/data/repository/core/support/MethodInvocationValidator.java

@@ -158,7 +158,7 @@ public class MethodInvocationValidator implements MethodInterceptor {
 		}
 
 		private static boolean requiresNoValue(MethodParameter parameter) {
-			return parameter.getParameterType().equals(Void.class) || parameter.getParameterType().equals(Void.TYPE);
+			return ReflectionUtils.isVoid(parameter.getParameterType());
 		}
 	}
 }

src/main/java/org/springframework/data/util/ReflectionUtils.java

@@ -82,6 +82,27 @@ public class ReflectionUtils {
 		}
 	}
 
+	/**
+	 * Check whether the given {@code type} represents a void type such as {@code void}, {@link Void} or Kotlin
+	 * {@code Unit}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return whether the given the type is a void type.
+	 * @since 2.2.10
+	 */
+	public static boolean isVoid(Class<?> type) {
+
+		if (type == Void.class || Void.TYPE == type) {
+			return true;
+		}
+
+		if (type.getName().equals("kotlin.Unit")) {
+			return true;
+		}
+
+		return false;
+	}
+
 	/**
 	 * A {@link FieldFilter} that has a description.
 	 *
@@ -394,7 +415,7 @@ public class ReflectionUtils {
 	 */
 	public static boolean isNullable(MethodParameter parameter) {
 
-		if (Void.class.equals(parameter.getParameterType()) || Void.TYPE.equals(parameter.getParameterType())) {
+		if (isVoid(parameter.getParameterType())) {
 			return true;
 		}
 

src/test/java/org/springframework/data/util/ReflectionUtilsUnitTests.java

@@ -17,6 +17,8 @@ package org.springframework.data.util;
 
 import static org.assertj.core.api.Assertions.*;
 
+import kotlin.Unit;
+
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 
@@ -163,6 +165,15 @@ public class ReflectionUtilsUnitTests {
 		assertThat(ReflectionUtils.isSupportedKotlinClass(TypeCreatingSyntheticClassKt.class)).isFalse();
 	}
 
+	@Test // DATACMNS-1779
+	public void shouldReportIsVoid() {
+
+		assertThat(ReflectionUtils.isVoid(Void.class)).isTrue();
+		assertThat(ReflectionUtils.isVoid(Void.TYPE)).isTrue();
+		assertThat(ReflectionUtils.isVoid(Unit.class)).isTrue();
+		assertThat(ReflectionUtils.isVoid(String.class)).isFalse();
+	}
+
 	static class Sample {
 
 		public String field;