Deprecate use of several bean factory methods for the same bean

See gh-31073

Author: jhoeller

spring-context/src/main/java/org/springframework/context/annotation/Configuration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -471,7 +471,10 @@
 	 * Switch this flag to {@code false} in order to allow for method overloading
 	 * according to those semantics, accepting the risk for accidental overlaps.
 	 * @since 6.0
+	 * @deprecated as of 7.0, always relying on {@code @Bean} unique methods,
+	 * just possibly with {@code Optional}/{@code ObjectProvider} arguments
 	 */
+	@Deprecated(since = "7.0")
 	boolean enforceUniqueMethods() default true;
 
 }

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java

@@ -292,6 +292,7 @@ private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
 		this.registry.registerBeanDefinition(beanName, beanDefToRegister);
 	}
 
+	@SuppressWarnings("NullAway")
 	protected boolean isOverriddenByExistingDefinition(BeanMethod beanMethod, String beanName) {
 		if (!this.registry.containsBeanDefinition(beanName)) {
 			return false;
@@ -302,21 +303,23 @@ protected boolean isOverriddenByExistingDefinition(BeanMethod beanMethod, String
 		// If the bean method is an overloaded case on the same configuration class,
 		// preserve the existing bean definition and mark it as overloaded.
 		if (existingBeanDef instanceof ConfigurationClassBeanDefinition ccbd) {
-			if (ccbd.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
-				if (ccbd.getFactoryMethodMetadata().getMethodName().equals(beanMethod.getMetadata().getMethodName())) {
-					ccbd.setNonUniqueFactoryMethodName(ccbd.getFactoryMethodMetadata().getMethodName());
-				}
-				else if (!this.registry.isBeanDefinitionOverridable(beanName)) {
-					throw new BeanDefinitionOverrideException(beanName,
-							new ConfigurationClassBeanDefinition(configClass, beanMethod.getMetadata(), beanName),
-							existingBeanDef,
-							"@Bean method override with same bean name but different method name: " + existingBeanDef);
-				}
+			if (!ccbd.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
+				return false;
+			}
+			if (ccbd.getFactoryMethodMetadata().getMethodName().equals(beanMethod.getMetadata().getMethodName())) {
+				ccbd.setNonUniqueFactoryMethodName(ccbd.getFactoryMethodMetadata().getMethodName());
 				return true;
 			}
-			else {
-				return false;
+			Map<String, Object> attributes =
+					configClass.getMetadata().getAnnotationAttributes(Configuration.class.getName());
+			if ((attributes != null && (Boolean) attributes.get("enforceUniqueMethods")) ||
+					!this.registry.isBeanDefinitionOverridable(beanName)) {
+				throw new BeanDefinitionOverrideException(beanName,
+						new ConfigurationClassBeanDefinition(configClass, beanMethod.getMetadata(), beanName),
+						existingBeanDef,
+						"@Bean method override with same bean name but different method name: " + existingBeanDef);
 			}
+			return true;
 		}
 
 		// A bean definition resulting from a component scan can be silently overridden

spring-context/src/test/java/org/springframework/context/annotation/configuration/ConfigurationClassProcessingTests.java

@@ -542,7 +542,7 @@ public TestBean bar() {
 	}
 
 
-	@Configuration
+	@Configuration(enforceUniqueMethods = false)
 	static class ConfigWithMethodNameMismatch {
 
 		@Bean(name = "foo") public TestBean foo1() {