Support Bean Overrides for non-singletons

Prior to this commit, the BeanOverrideBeanFactoryPostProcessor rejected
any attempt to override a non-singleton bean; however, due to interest
from the community, we have decided to provide support for overriding
non-singleton beans via the Bean Override mechanism — for example, when
using @⁠MockitoBean, @⁠MockitoSpyBean, and @⁠TestBean.

With this commit, we now support Bean Overrides for non-singletons: for
standard JVM runtimes as well as AOT processing and AOT runtimes. This
commit also documents that non-singletons will effectively be converted
to singletons when overridden and logs a warning similar to the
following.

WARN: BeanOverrideBeanFactoryPostProcessor - Converting 'prototype' scoped bean definition 'myBean' to a singleton.

See gh-33602
See gh-32933
See gh-33800
Closes gh-35574

spring-test/src/test/java/org/springframework/test/context/bean/override/BeanOverrideBeanFactoryPostProcessorTests.java

@@ -321,7 +321,7 @@ class BeanOverrideBeanFactoryPostProcessorTests {
 	}
 
 	@Test
-	void replaceBeanByNameWithMatchingBeanDefinitionWithPrototypeScopeFails() {
+	void replaceBeanByNameWithMatchingBeanDefinitionWithPrototypeScope() {
 		String beanName = "descriptionBean";
 
 		AnnotationConfigApplicationContext context = createContext(ByNameTestCase.class);
@@ -329,13 +329,13 @@ class BeanOverrideBeanFactoryPostProcessorTests {
 		definition.setScope(BeanDefinition.SCOPE_PROTOTYPE);
 		context.registerBeanDefinition(beanName, definition);
 
-		assertThatIllegalStateException()
-				.isThrownBy(context::refresh)
-				.withMessage("Unable to override bean 'descriptionBean': only singleton beans can be overridden.");
+		assertThatNoException().isThrownBy(context::refresh);
+		assertThat(context.isSingleton(beanName)).as("isSingleton").isTrue();
+		assertThat(context.getBean(beanName, String.class)).isEqualTo("overridden");
 	}
 
 	@Test
-	void replaceBeanByNameWithMatchingBeanDefinitionWithCustomScopeFails() {
+	void replaceBeanByNameWithMatchingBeanDefinitionWithCustomScope() {
 		String beanName = "descriptionBean";
 		String scope = "customScope";
 
@@ -346,22 +346,22 @@ class BeanOverrideBeanFactoryPostProcessorTests {
 		definition.setScope(scope);
 		context.registerBeanDefinition(beanName, definition);
 
-		assertThatIllegalStateException()
-				.isThrownBy(context::refresh)
-				.withMessage("Unable to override bean 'descriptionBean': only singleton beans can be overridden.");
+		assertThatNoException().isThrownBy(context::refresh);
+		assertThat(context.isSingleton(beanName)).as("isSingleton").isTrue();
+		assertThat(context.getBean(beanName, String.class)).isEqualTo("overridden");
 	}
 
 	@Test
-	void replaceBeanByNameWithMatchingBeanDefinitionForPrototypeScopedFactoryBeanFails() {
+	void replaceBeanByNameWithMatchingBeanDefinitionForPrototypeScopedFactoryBean() {
 		String beanName = "messageServiceBean";
 		AnnotationConfigApplicationContext context = createContext(MessageServiceTestCase.class);
 		RootBeanDefinition factoryBeanDefinition = new RootBeanDefinition(SingletonMessageServiceFactoryBean.class);
 		factoryBeanDefinition.setScope(BeanDefinition.SCOPE_PROTOTYPE);
 		context.registerBeanDefinition(beanName, factoryBeanDefinition);
 
-		assertThatIllegalStateException()
-				.isThrownBy(context::refresh)
-				.withMessage("Unable to override bean 'messageServiceBean': only singleton beans can be overridden.");
+		assertThatNoException().isThrownBy(context::refresh);
+		assertThat(context.isSingleton(beanName)).as("isSingleton").isTrue();
+		assertThat(context.getBean(beanName, MessageService.class).getMessage()).isEqualTo("overridden");
 	}
 
 	@Test

spring-test/src/test/java/org/springframework/test/context/bean/override/convention/TestBeanByNameLookupIntegrationTests.java

@@ -21,8 +21,10 @@ import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -43,6 +45,10 @@ public class TestBeanByNameLookupIntegrationTests {
 	@TestBean(name = "methodRenamed1", methodName = "field")
 	String methodRenamed1;
 
+	@TestBean("prototypeScoped")
+	String prototypeScoped;
+
+
 	static String field() {
 		return "fieldOverride";
 	}
@@ -51,6 +57,11 @@ public class TestBeanByNameLookupIntegrationTests {
 		return "nestedFieldOverride";
 	}
 
+	static String prototypeScoped() {
+		return "prototypeScopedOverride";
+	}
+
+
 	@Test
 	void fieldHasOverride(ApplicationContext ctx) {
 		assertThat(ctx.getBean("field")).as("applicationContext").isEqualTo("fieldOverride");
@@ -63,6 +74,13 @@ public class TestBeanByNameLookupIntegrationTests {
 		assertThat(methodRenamed1).as("injection point").isEqualTo("fieldOverride");
 	}
 
+	@Test
+	void fieldForPrototypeHasOverride(ConfigurableApplicationContext ctx) {
+		assertThat(ctx.getBeanFactory().getBeanDefinition("prototypeScoped").isSingleton()).as("isSingleton").isTrue();
+		assertThat(ctx.getBean("prototypeScoped")).as("applicationContext").isEqualTo("prototypeScopedOverride");
+		assertThat(prototypeScoped).as("injection point").isEqualTo("prototypeScopedOverride");
+	}
+
 
 	@Nested
 	@DisplayName("With @TestBean in enclosing class and in @Nested class")
@@ -180,6 +198,12 @@ public class TestBeanByNameLookupIntegrationTests {
 		String bean4() {
 			return "NestedProd";
 		}
+
+		@Bean("prototypeScoped")
+		@Scope("prototype")
+		String bean5() {
+			return "PrototypeProd";
+		}
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/bean/override/convention/TestBeanByTypeLookupIntegrationTests.java

@@ -20,8 +20,10 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.test.context.bean.override.example.CustomQualifier;
 import org.springframework.test.context.bean.override.example.ExampleService;
 import org.springframework.test.context.bean.override.example.RealExampleService;
@@ -53,6 +55,9 @@ public class TestBeanByTypeLookupIntegrationTests {
 	@CustomQualifier
 	StringBuilder anyNameForStringBuilder2;
 
+	@TestBean
+	Number prototypeNumber;
+
 
 	static MessageService messageService() {
 		return () -> "mocked nonexistent bean definition";
@@ -70,6 +75,9 @@ public class TestBeanByTypeLookupIntegrationTests {
 		return new StringBuilder("CustomQualifier TestBean String");
 	}
 
+	static Number prototypeNumber() {
+		return 42;
+	}
 
 	@Test
 	void overrideIsFoundByTypeForNonexistentBeanDefinition(ApplicationContext ctx) {
@@ -101,6 +109,13 @@ public class TestBeanByTypeLookupIntegrationTests {
 		assertThat(ctx.getBean("one")).as("no qualifier needed").hasToString("Prod One");
 	}
 
+	@Test
+	void overrideIsFoundByTypeForPrototypeBeanDefinition(ConfigurableApplicationContext ctx) {
+		assertThat(ctx.getBeanFactory().getBeanDefinition("prototypeNumber").isSingleton()).as("isSingleton").isTrue();
+		assertThat(this.prototypeNumber).isSameAs(ctx.getBean(Number.class));
+		assertThat(this.prototypeNumber).isEqualTo(42);
+	}
+
 
 	@Configuration(proxyBeanMethods = false)
 	static class Config {
@@ -126,6 +141,12 @@ public class TestBeanByTypeLookupIntegrationTests {
 		StringBuilder beanString3() {
 			return new StringBuilder("Prod Three");
 		}
+
+		@Bean
+		@Scope("prototype")
+		Number prototypeNumber() {
+			return -999;
+		}
 	}
 
 	@FunctionalInterface

spring-test/src/test/java/org/springframework/test/context/bean/override/mockito/MockitoBeanByNameLookupIntegrationTests.java

@@ -23,8 +23,10 @@ import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.test.context.bean.override.example.ExampleService;
 import org.springframework.test.context.bean.override.example.RealExampleService;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
@@ -48,6 +50,9 @@ public class MockitoBeanByNameLookupIntegrationTests {
 	@MockitoBean("nonExistingBean")
 	ExampleService nonExisting;
 
+	@MockitoBean("prototypeScoped")
+	ExampleService prototypeScoped;
+
 
 	@Test
 	void fieldAndRenamedFieldHaveSameOverride(ApplicationContext ctx) {
@@ -69,6 +74,17 @@ public class MockitoBeanByNameLookupIntegrationTests {
 		assertThat(nonExisting.greeting()).as("mocked greeting").isNull();
 	}
 
+	@Test
+	void fieldForPrototypeHasOverride(ConfigurableApplicationContext ctx) {
+		assertThat(ctx.getBean("prototypeScoped"))
+				.isInstanceOf(ExampleService.class)
+				.satisfies(MockitoAssertions::assertIsMock)
+				.isSameAs(prototypeScoped);
+		assertThat(ctx.getBeanFactory().getBeanDefinition("prototypeScoped").isSingleton()).as("isSingleton").isTrue();
+
+		assertThat(prototypeScoped.greeting()).as("mocked greeting").isNull();
+	}
+
 
 	@Nested
 	@DisplayName("With @MockitoBean in enclosing class and in @Nested class")
@@ -139,6 +155,12 @@ public class MockitoBeanByNameLookupIntegrationTests {
 		ExampleService bean2() {
 			return new RealExampleService("Hello Nested Field");
 		}
+
+		@Bean("prototypeScoped")
+		@Scope("prototype")
+		ExampleService bean3() {
+			return new RealExampleService("Hello Prototype Field");
+		}
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/bean/override/mockito/MockitoBeanByTypeLookupIntegrationTests.java

@@ -21,8 +21,10 @@ import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.core.annotation.Order;
 import org.springframework.test.context.bean.override.example.CustomQualifier;
 import org.springframework.test.context.bean.override.example.ExampleService;
@@ -63,6 +65,10 @@ public class MockitoBeanByTypeLookupIntegrationTests {
 	@CustomQualifier
 	StringBuilder ambiguousMeta;
 
+	@MockitoBean
+	YetAnotherService yetAnotherService;
+
+
 	@Test
 	void mockIsCreatedWhenNoCandidateIsFound() {
 		assertIsMock(this.serviceIsNotABean);
@@ -122,11 +128,30 @@ public class MockitoBeanByTypeLookupIntegrationTests {
 		verifyNoMoreInteractions(this.ambiguousMeta);
 	}
 
+	@Test
+	void overrideIsFoundByTypeForPrototype(ConfigurableApplicationContext ctx) {
+		assertThat(this.yetAnotherService)
+				.satisfies(MockitoAssertions::assertIsMock)
+				.isSameAs(ctx.getBean("YAS"))
+				.isSameAs(ctx.getBean(YetAnotherService.class));
+		assertThat(ctx.getBeanFactory().getBeanDefinition("YAS").isSingleton()).as("isSingleton").isTrue();
+
+		when(this.yetAnotherService.hello()).thenReturn("Mocked greeting");
+
+		assertThat(this.yetAnotherService.hello()).isEqualTo("Mocked greeting");
+		verify(this.yetAnotherService, times(1)).hello();
+		verifyNoMoreInteractions(this.yetAnotherService);
+	}
+
 
 	public interface AnotherService {
 
 		String hello();
+	}
 
+	public interface YetAnotherService {
+
+		String hello();
 	}
 
 	@Configuration(proxyBeanMethods = false)
@@ -150,6 +175,12 @@ public class MockitoBeanByTypeLookupIntegrationTests {
 		StringBuilder bean3() {
 			return new StringBuilder("bean3");
 		}
+
+		@Bean("YAS")
+		@Scope("prototype")
+		YetAnotherService bean4() {
+			return () -> "Production Hello";
+		}
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/bean/override/mockito/MockitoSpyBeanByNameLookupIntegrationTests.java

@@ -23,8 +23,10 @@ import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.test.context.bean.override.example.ExampleService;
 import org.springframework.test.context.bean.override.example.RealExampleService;
 import org.springframework.test.context.bean.override.mockito.MockitoSpyBeanByNameLookupIntegrationTests.Config;
@@ -46,6 +48,9 @@ public class MockitoSpyBeanByNameLookupIntegrationTests {
 	@MockitoSpyBean("field1")
 	ExampleService field;
 
+	@MockitoSpyBean("field3")
+	ExampleService prototypeScoped;
+
 
 	@Test
 	void fieldHasOverride(ApplicationContext ctx) {
@@ -57,6 +62,16 @@ public class MockitoSpyBeanByNameLookupIntegrationTests {
 		assertThat(field.greeting()).isEqualTo("bean1");
 	}
 
+	@Test
+	void fieldForPrototypeHasOverride(ConfigurableApplicationContext ctx) {
+		assertThat(ctx.getBean("field3"))
+				.isInstanceOf(ExampleService.class)
+				.satisfies(MockitoAssertions::assertIsSpy)
+				.isSameAs(prototypeScoped);
+		assertThat(ctx.getBeanFactory().getBeanDefinition("field3").isSingleton()).as("isSingleton").isTrue();
+
+		assertThat(prototypeScoped.greeting()).isEqualTo("bean3");
+	}
 
 	@Nested
 	@DisplayName("With @MockitoSpyBean in enclosing class and in @Nested class")
@@ -102,6 +117,12 @@ public class MockitoSpyBeanByNameLookupIntegrationTests {
 		ExampleService bean2() {
 			return new RealExampleService("bean2");
 		}
+
+		@Bean("field3")
+		@Scope("prototype")
+		ExampleService bean3() {
+			return new RealExampleService("bean3");
+		}
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/bean/override/mockito/MockitoSpyBeanByTypeLookupIntegrationTests.java

@@ -20,8 +20,10 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
 import org.springframework.core.annotation.Order;
 import org.springframework.test.context.bean.override.example.CustomQualifier;
 import org.springframework.test.context.bean.override.example.ExampleService;
@@ -55,6 +57,9 @@ public class MockitoSpyBeanByTypeLookupIntegrationTests {
 	@CustomQualifier
 	StringHolder ambiguousMeta;
 
+	@MockitoSpyBean
+	AnotherService prototypeService;
+
 
 	@Test
 	void overrideIsFoundByType(ApplicationContext ctx) {
@@ -102,6 +107,19 @@ public class MockitoSpyBeanByTypeLookupIntegrationTests {
 		verifyNoMoreInteractions(this.ambiguousMeta);
 	}
 
+	@Test
+	void overrideIsFoundByTypeForPrototype(ConfigurableApplicationContext ctx) {
+		assertThat(this.prototypeService)
+				.satisfies(MockitoAssertions::assertIsSpy)
+				.isSameAs(ctx.getBean("anotherService"))
+				.isSameAs(ctx.getBean(AnotherService.class));
+		assertThat(ctx.getBeanFactory().getBeanDefinition("anotherService").isSingleton()).as("isSingleton").isTrue();
+
+		assertThat(this.prototypeService.hello()).isEqualTo("Production Hello");
+		verify(this.prototypeService).hello();
+		verifyNoMoreInteractions(this.prototypeService);
+	}
+
 
 	@Configuration(proxyBeanMethods = false)
 	static class Config {
@@ -124,6 +142,12 @@ public class MockitoSpyBeanByTypeLookupIntegrationTests {
 		StringHolder bean3() {
 			return new StringHolder("bean3");
 		}
+
+		@Bean("anotherService")
+		@Scope("prototype")
+		AnotherService bean4() {
+			return new DefaultAnotherService("Production Hello");
+		}
 	}
 
 	static class StringHolder {
@@ -143,4 +167,17 @@ public class MockitoSpyBeanByTypeLookupIntegrationTests {
 		}
 	}
 
+	public interface AnotherService {
+
+		String hello();
+	}
+
+	record DefaultAnotherService(String message) implements AnotherService {
+
+		@Override
+		public String hello() {
+			return this.message;
+		}
+	}
+
 }