Use the bean factory to get the type produced by a factory bean

Previously, we only looked at the OBJECT_TYPE_ATTRIBUTE on the
factory bean's definition. This did not work for situations
where the information's provided by the definition's target type
rather than the attribute.

Rather than manually considering the target type in addition to
the existing consideration of the attribute, we now ask the bean
factory for the type that will be produced by the factory bean
instead. This should insulate us from any changes and
enhancements in Framework in the future.

Fixes gh-40234

Author: wilkinsona

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/mock/mockito/MockitoPostProcessor.java

@@ -254,9 +254,8 @@ private Set<String> getExistingBeans(ConfigurableListableBeanFactory beanFactory
 		Class<?> type = resolvableType.resolve(Object.class);
 		for (String beanName : beanFactory.getBeanNamesForType(FactoryBean.class, true, false)) {
 			beanName = BeanFactoryUtils.transformedBeanName(beanName);
-			BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanName);
-			Object attribute = beanDefinition.getAttribute(FactoryBean.OBJECT_TYPE_ATTRIBUTE);
-			if (resolvableType.equals(attribute) || type.equals(attribute)) {
+			Class<?> producedType = beanFactory.getType(beanName, false);
+			if (type.equals(producedType)) {
 				beans.add(beanName);
 			}
 		}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/mock/mockito/SpyBeanOnTestFieldForExistingGenericBeanProducedByFactoryBeanIntegrationTests.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2012-2022 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.boot.test.mock.mockito;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mockito;
+
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.boot.test.mock.mockito.example.ExampleGenericService;
+import org.springframework.boot.test.mock.mockito.example.SimpleExampleStringGenericService;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Test {@link SpyBean @SpyBean} on a test class field can be used to replace an existing
+ * bean with generics that's produced by a factory bean.
+ *
+ * @author Andy Wilkinson
+ */
+@ExtendWith(SpringExtension.class)
+class SpyBeanOnTestFieldForExistingGenericBeanProducedByFactoryBeanIntegrationTests {
+
+	// gh-40234
+
+	@SpyBean(name = "exampleService")
+	private ExampleGenericService<String> exampleService;
+
+	@Test
+	void testSpying() {
+		assertThat(Mockito.mockingDetails(this.exampleService).isSpy()).isTrue();
+		assertThat(Mockito.mockingDetails(this.exampleService).getMockCreationSettings().getSpiedInstance())
+			.isInstanceOf(SimpleExampleStringGenericService.class);
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@Import(FactoryBeanRegistrar.class)
+	static class SpyBeanOnTestFieldForExistingBeanConfig {
+
+	}
+
+	static class FactoryBeanRegistrar implements ImportBeanDefinitionRegistrar {
+
+		@Override
+		public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
+				BeanDefinitionRegistry registry) {
+			RootBeanDefinition definition = new RootBeanDefinition(ExampleGenericServiceFactoryBean.class);
+			definition.setTargetType(ResolvableType.forClassWithGenerics(ExampleGenericServiceFactoryBean.class, null,
+					ExampleGenericService.class));
+			registry.registerBeanDefinition("exampleService", definition);
+		}
+
+	}
+
+	static class ExampleGenericServiceFactoryBean<T, U extends ExampleGenericService<T>> implements FactoryBean<U> {
+
+		@SuppressWarnings("unchecked")
+		@Override
+		public U getObject() throws Exception {
+			return (U) new SimpleExampleStringGenericService();
+		}
+
+		@Override
+		@SuppressWarnings("rawtypes")
+		public Class<ExampleGenericService> getObjectType() {
+			return ExampleGenericService.class;
+		}
+
+	}
+
+}