Unwrap nested generic type within FactoryBean target type if necessary

Closes gh-29385

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/factory/support/GenericTypeAwareAutowireCandidateResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -102,6 +102,17 @@ protected boolean checkGenericTypeMatch(BeanDefinitionHolder bdHolder, Dependenc
 					}
 				}
 			}
+			else {
+				// Pre-existing target type: In case of a generic FactoryBean type,
+				// unwrap nested generic type when matching a non-FactoryBean type.
+				Class<?> resolvedClass = targetType.resolve();
+				if (resolvedClass != null && FactoryBean.class.isAssignableFrom(resolvedClass)) {
+					Class<?> typeToBeMatched = dependencyType.resolve();
+					if (typeToBeMatched != null && !FactoryBean.class.isAssignableFrom(typeToBeMatched)) {
+						targetType = targetType.getGeneric();
+					}
+				}
+			}
 		}
 
 		if (targetType == null) {

spring-context/src/test/java/org/springframework/context/annotation/AnnotationConfigApplicationContextTests.java

@@ -16,7 +16,9 @@
 
 package org.springframework.context.annotation;
 
+import java.util.Collections;
 import java.util.Map;
+import java.util.Set;
 import java.util.regex.Pattern;
 
 import org.junit.jupiter.api.Test;
@@ -372,8 +374,8 @@ void individualBeanWithFactoryBeanSupplier() {
 		context.registerBean("fb", NonInstantiatedFactoryBean.class, NonInstantiatedFactoryBean::new, bd -> bd.setLazyInit(true));
 		context.refresh();
 
-		assertThat(context.getType("fb")).isEqualTo(String.class);
 		assertThat(context.getType("&fb")).isEqualTo(NonInstantiatedFactoryBean.class);
+		assertThat(context.getType("fb")).isEqualTo(String.class);
 		assertThat(context.getBeanNamesForType(FactoryBean.class)).hasSize(1);
 		assertThat(context.getBeanNamesForType(NonInstantiatedFactoryBean.class)).hasSize(1);
 	}
@@ -388,25 +390,55 @@ void individualBeanWithFactoryBeanSupplierAndTargetType() {
 		context.registerBeanDefinition("fb", bd);
 		context.refresh();
 
-		assertThat(context.getType("fb")).isEqualTo(String.class);
 		assertThat(context.getType("&fb")).isEqualTo(FactoryBean.class);
+		assertThat(context.getType("fb")).isEqualTo(String.class);
 		assertThat(context.getBeanNamesForType(FactoryBean.class)).hasSize(1);
 		assertThat(context.getBeanNamesForType(NonInstantiatedFactoryBean.class)).isEmpty();
 	}
 
+	@Test
+	void individualBeanWithFactoryBeanTypeAsTargetType() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		RootBeanDefinition bd1 = new RootBeanDefinition();
+		bd1.setBeanClass(SetFactoryBean.class);
+		bd1.setTargetType(ResolvableType.forClassWithGenerics(FactoryBean.class, ResolvableType.forClassWithGenerics(Set.class, String.class)));
+		bd1.setLazyInit(true);
+		context.registerBeanDefinition("fb1", bd1);
+		RootBeanDefinition bd2 = new RootBeanDefinition();
+		bd2.setBeanClass(UntypedFactoryBean.class);
+		bd2.setTargetType(ResolvableType.forClassWithGenerics(FactoryBean.class, ResolvableType.forClassWithGenerics(Set.class, Integer.class)));
+		bd2.setLazyInit(true);
+		context.registerBeanDefinition("fb2", bd2);
+		context.registerBeanDefinition("ip", new RootBeanDefinition(FactoryBeanInjectionPoints.class));
+		context.refresh();
+
+		assertThat(context.getType("&fb1")).isEqualTo(SetFactoryBean.class);
+		assertThat(context.getType("fb1")).isEqualTo(Set.class);
+		assertThat(context.getBeanNamesForType(FactoryBean.class)).hasSize(2);
+		assertThat(context.getBeanNamesForType(SetFactoryBean.class)).hasSize(1);
+		assertThat(context.getBean("ip", FactoryBeanInjectionPoints.class).factoryBean).isSameAs(context.getBean("&fb1"));
+		assertThat(context.getBean("ip", FactoryBeanInjectionPoints.class).factoryResult).isSameAs(context.getBean("fb1"));
+	}
+
 	@Test
 	void individualBeanWithFactoryBeanObjectTypeAsTargetType() {
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
-		RootBeanDefinition bd = new RootBeanDefinition();
-		bd.setBeanClass(TypedFactoryBean.class);
-		bd.setTargetType(String.class);
-		context.registerBeanDefinition("fb", bd);
+		RootBeanDefinition bd1 = new RootBeanDefinition();
+		bd1.setBeanClass(SetFactoryBean.class);
+		bd1.setTargetType(ResolvableType.forClassWithGenerics(Set.class, String.class));
+		context.registerBeanDefinition("fb1", bd1);
+		RootBeanDefinition bd2 = new RootBeanDefinition();
+		bd2.setBeanClass(UntypedFactoryBean.class);
+		bd2.setTargetType(ResolvableType.forClassWithGenerics(Set.class, Integer.class));
+		context.registerBeanDefinition("fb2", bd2);
+		context.registerBeanDefinition("ip", new RootBeanDefinition(FactoryResultInjectionPoint.class));
 		context.refresh();
 
-		assertThat(context.getType("&fb")).isEqualTo(TypedFactoryBean.class);
-		assertThat(context.getType("fb")).isEqualTo(String.class);
-		assertThat(context.getBeanNamesForType(FactoryBean.class)).hasSize(1);
-		assertThat(context.getBeanNamesForType(TypedFactoryBean.class)).hasSize(1);
+		assertThat(context.getType("&fb1")).isEqualTo(SetFactoryBean.class);
+		assertThat(context.getType("fb1")).isEqualTo(Set.class);
+		assertThat(context.getBeanNamesForType(FactoryBean.class)).hasSize(2);
+		assertThat(context.getBeanNamesForType(SetFactoryBean.class)).hasSize(1);
+		assertThat(context.getBean("ip", FactoryResultInjectionPoint.class).factoryResult).isSameAs(context.getBean("fb1"));
 	}
 
 	@Test
@@ -630,6 +662,36 @@ public boolean isSingleton() {
 			return false;
 		}
 	}
+
+	static class SetFactoryBean implements FactoryBean<Set<String>> {
+
+		@Override
+		public Set<String> getObject() {
+			return Collections.emptySet();
+		}
+
+		@Override
+		public Class<?> getObjectType() {
+			return Set.class;
+		}
+
+		@Override
+		public boolean isSingleton() {
+			return true;
+		}
+	}
+
+	static class FactoryResultInjectionPoint {
+
+		@Autowired
+		Set<String> factoryResult;
+	}
+
+	static class FactoryBeanInjectionPoints extends FactoryResultInjectionPoint {
+
+		@Autowired
+		FactoryBean<Set<String>> factoryBean;
+	}
 }
 
 class TestBean {