Specialize Kotlin property accessors in KotlinBeanInfoFactory.

We now attempt to detect property accessors for properties declared in Kotlin that do not have a Kotlin-style accessor but one that instead comes from an interface.

Also, we specialize accessor methods that are inherited from a Java superclass but override accessors in the Kotlin realm.

Closes spring-projects#3140
Closes spring-projects#3146

Author: mp911de

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

@@ -29,15 +29,19 @@
 import java.beans.SimpleBeanInfo;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
-import java.util.Arrays;
+import java.lang.reflect.Type;
 import java.util.Collection;
-import java.util.LinkedHashSet;
-import java.util.Set;
+import java.util.LinkedHashMap;
+import java.util.Map;
 
 import org.springframework.beans.BeanInfoFactory;
 import org.springframework.beans.BeanUtils;
 import org.springframework.core.KotlinDetector;
 import org.springframework.core.Ordered;
+import org.springframework.lang.Nullable;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link BeanInfoFactory} specific to Kotlin types using Kotlin reflection to determine bean properties.
@@ -62,7 +66,7 @@ public BeanInfo getBeanInfo(Class<?> beanClass) throws IntrospectionException {
 
 		KClass<?> kotlinClass = JvmClassMappingKt.getKotlinClass(beanClass);
 		Collection<KCallable<?>> members = kotlinClass.getMembers();
-		Set<PropertyDescriptor> pds = new LinkedHashSet<>(members.size());
+		Map<String, PropertyDescriptor> descriptors = new LinkedHashMap<>(members.size(), 1.f);
 
 		for (KCallable<?> member : members) {
 
@@ -71,6 +75,16 @@ public BeanInfo getBeanInfo(Class<?> beanClass) throws IntrospectionException {
 				Method getter = ReflectJvmMapping.getJavaGetter(property);
 				Method setter = property instanceof KMutableProperty<?> kmp ? ReflectJvmMapping.getJavaSetter(kmp) : null;
 
+				if (getter == null) {
+					Type javaType = ReflectJvmMapping.getJavaType(property.getReturnType());
+					getter = ReflectionUtils.findMethod(beanClass,
+							javaType == Boolean.TYPE ? "is" : "get" + StringUtils.capitalize(property.getName()));
+				}
+
+				if (getter != null) {
+					getter = ClassUtils.getMostSpecificMethod(getter, beanClass);
+				}
+
 				if (getter != null && (Modifier.isStatic(getter.getModifiers()) || getter.getParameterCount() != 0)) {
 					continue;
 				}
@@ -82,7 +96,7 @@ public BeanInfo getBeanInfo(Class<?> beanClass) throws IntrospectionException {
 					}
 				}
 
-				pds.add(new PropertyDescriptor(property.getName(), getter, setter));
+				descriptors.put(property.getName(), new PropertyDescriptor(property.getName(), getter, setter));
 			}
 		}
 
@@ -95,9 +109,17 @@ public BeanInfo getBeanInfo(Class<?> beanClass) throws IntrospectionException {
 		if (javaClass != Object.class) {
 
 			PropertyDescriptor[] javaPropertyDescriptors = BeanUtils.getPropertyDescriptors(javaClass);
-			pds.addAll(Arrays.asList(javaPropertyDescriptors));
+
+			for (PropertyDescriptor descriptor : javaPropertyDescriptors) {
+
+				descriptor = new PropertyDescriptor(descriptor.getName(), specialize(beanClass, descriptor.getReadMethod()),
+						specialize(beanClass, descriptor.getWriteMethod()));
+				descriptors.put(descriptor.getName(), descriptor);
+			}
 		}
 
+		PropertyDescriptor[] propertyDescriptors = descriptors.values().toArray(new PropertyDescriptor[0]);
+
 		return new SimpleBeanInfo() {
 			@Override
 			public BeanDescriptor getBeanDescriptor() {
@@ -106,11 +128,21 @@ public BeanDescriptor getBeanDescriptor() {
 
 			@Override
 			public PropertyDescriptor[] getPropertyDescriptors() {
-				return pds.toArray(new PropertyDescriptor[0]);
+				return propertyDescriptors;
 			}
 		};
 	}
 
+	@Nullable
+	private static Method specialize(Class<?> beanClass, @Nullable Method method) {
+
+		if (method == null) {
+			return method;
+		}
+
+		return ClassUtils.getMostSpecificMethod(method, beanClass);
+	}
+
 	@Override
 	public int getOrder() {
 		return LOWEST_PRECEDENCE - 10; // leave some space for customizations.

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

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2024 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.util;
+
+public class Animal {
+
+	private String name;
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+}

src/test/kotlin/org/springframework/data/util/KotlinBeanInfoFactoryUnitTests.kt

@@ -18,6 +18,8 @@ package org.springframework.data.util
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
 import org.springframework.beans.BeanUtils
+import org.springframework.data.annotation.Id
+import org.springframework.data.domain.Persistable
 import org.springframework.data.repository.Repository
 import org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport
 import org.springframework.data.repository.core.support.RepositoryFactorySupport
@@ -95,9 +97,11 @@ class KotlinBeanInfoFactoryUnitTests {
 	@Test // GH-2994
 	internal fun includesPropertiesFromJavaSupertypes() {
 
-		val pds = BeanUtils.getPropertyDescriptors(MyRepositoryFactoryBeanImpl::class.java)
+		val pds =
+			BeanUtils.getPropertyDescriptors(MyRepositoryFactoryBeanImpl::class.java)
 
-		assertThat(pds).extracting("name").contains("myQueryLookupStrategyKey", "repositoryBaseClass")
+		assertThat(pds).extracting("name")
+			.contains("myQueryLookupStrategyKey", "repositoryBaseClass")
 	}
 
 	@Test // GH-2993
@@ -110,6 +114,22 @@ class KotlinBeanInfoFactoryUnitTests {
 		assertThat(pds[0].readMethod).isNotNull()
 	}
 
+	@Test // GH-3140
+	internal fun specializesBeanMethods() {
+
+		var pds = BeanUtils.getPropertyDescriptors(Entity::class.java)
+
+		assertThat(pds.find { it.name == "id" }!!.readMethod!!.declaringClass).isEqualTo(
+			Entity::class.java
+		)
+
+		pds = BeanUtils.getPropertyDescriptors(DogEntity::class.java)
+
+		assertThat(pds.find { it.name == "name" }!!.readMethod!!.declaringClass).isEqualTo(
+			DogEntity::class.java
+		)
+	}
+
 	data class SimpleDataClass(val id: String, var name: String)
 
 	@JvmInline
@@ -127,7 +147,8 @@ class KotlinBeanInfoFactoryUnitTests {
 		Foo, Bar
 	}
 
-	class MyRepositoryFactoryBeanImpl<R, E, I>(repository: Class<R>) : RepositoryFactoryBeanSupport<R, E, I>(repository)
+	class MyRepositoryFactoryBeanImpl<R, E, I>(repository: Class<R>) :
+		RepositoryFactoryBeanSupport<R, E, I>(repository)
 			where R : Repository<E, I>, E : Any, I : Any {
 
 		private var myQueryLookupStrategyKey: String
@@ -149,4 +170,23 @@ class KotlinBeanInfoFactoryUnitTests {
 		override var end: Long = -1L
 			protected set
 	}
+
+	class Entity(
+		private val id: Long? = null,
+
+		val name: String
+	) : Persistable<Long> {
+
+		override fun getId(): Long? = id
+
+		override fun isNew(): Boolean = id == null
+	}
+
+	open class DogEntity : Animal() {
+
+		@Id
+		override fun getName(): String {
+			return super.getName()
+		}
+	}
 }