Allow registration of bean factory contributors via spring.factories

Closes gh-28342

spring-context/src/main/java/org/springframework/context/generator/ApplicationContextAotGenerator.java

@@ -42,6 +42,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.core.OrderComparator;
+import org.springframework.core.io.support.SpringFactoriesLoader;
 import org.springframework.javapoet.CodeBlock;
 import org.springframework.javapoet.MethodSpec;
 import org.springframework.javapoet.ParameterizedTypeName;
@@ -150,7 +151,8 @@ public class ApplicationContextAotGenerator {
 		for (String ppName : postProcessorNames) {
 			postProcessors.add(beanFactory.getBean(ppName, AotContributingBeanFactoryPostProcessor.class));
 		}
-		postProcessors.add(new RuntimeHintsPostProcessor());
+		postProcessors.addAll(SpringFactoriesLoader.loadFactories(AotContributingBeanFactoryPostProcessor.class,
+				beanFactory.getBeanClassLoader()));
 		sortPostProcessors(postProcessors, beanFactory);
 		return postProcessors;
 	}

spring-context/src/main/resources/META-INF/spring.factories

@@ -0,0 +1,2 @@
+org.springframework.beans.factory.generator.AotContributingBeanFactoryPostProcessor= \
+org.springframework.context.generator.RuntimeHintsPostProcessor

spring-context/src/test/java/org/springframework/context/generator/ApplicationContextAotGeneratorTests.java

@@ -18,6 +18,8 @@ package org.springframework.context.generator;
 
 import java.io.IOException;
 import java.io.StringWriter;
+import java.net.URL;
+import java.util.Enumeration;
 import java.util.function.BiPredicate;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -148,6 +150,27 @@ class ApplicationContextAotGeneratorTests {
 				""");
 	}
 
+	@Test
+	void generateApplicationContextLoadsBeanFactoryContributors() {
+		GeneratedTypeContext generationContext = createGenerationContext();
+		ApplicationContextAotGenerator generator = new ApplicationContextAotGenerator();
+		GenericApplicationContext applicationContext = new GenericApplicationContext();
+		applicationContext.setClassLoader(
+				new TestSpringFactoriesClassLoader("bean-factory-contributors.factories"));
+		generator.generateApplicationContext(applicationContext, generationContext);
+		assertThat(write(generationContext.getMainGeneratedType())).contains("""
+				public class Test implements ApplicationContextInitializer<GenericApplicationContext> {
+					@Override
+					public void initialize(GenericApplicationContext context) {
+						// infrastructure
+						DefaultListableBeanFactory beanFactory = context.getDefaultListableBeanFactory();
+						beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
+						// Test
+					}
+				}
+				""");
+	}
+
 	@Test
 	void generateApplicationContextApplyContributionAsIsWithNewLineAtTheEnd() {
 		GenericApplicationContext applicationContext = new GenericApplicationContext();
@@ -211,8 +234,7 @@ class ApplicationContextAotGeneratorTests {
 		GeneratedTypeContext generationContext = createGenerationContext();
 		GenericApplicationContext applicationContext = new GenericApplicationContext();
 		DefaultListableBeanFactory beanFactory = applicationContext.getDefaultListableBeanFactory();
-		@SuppressWarnings("unchecked")
+		BiPredicate<String, BeanDefinition> excludeFilter = mockExcludeFilter();
-		BiPredicate<String, BeanDefinition> excludeFilter = mock(BiPredicate.class);
 		given(excludeFilter.test(eq("bean1"), any(BeanDefinition.class))).willReturn(Boolean.FALSE);
 		given(excludeFilter.test(eq("bean2"), any(BeanDefinition.class))).willReturn(Boolean.TRUE);
 		applicationContext.registerBeanDefinition("bean2", new RootBeanDefinition(SimpleComponent.class));
@@ -228,6 +250,11 @@ class ApplicationContextAotGeneratorTests {
 	}
 
 
+	@SuppressWarnings("unchecked")
+	private BiPredicate<String, BeanDefinition> mockExcludeFilter() {
+		return mock(BiPredicate.class);
+	}
+
 	@SuppressWarnings("rawtypes")
 	private void compile(GenericApplicationContext applicationContext, Consumer<ApplicationContextInitializer> initializer) {
 		DefaultGeneratedTypeContext generationContext = createGenerationContext();
@@ -306,6 +333,15 @@ class ApplicationContextAotGeneratorTests {
 
 	}
 
+	static class TextAotContributingBeanFactoryPostProcessor implements AotContributingBeanFactoryPostProcessor {
+
+		@Override
+		public BeanFactoryContribution contribute(ConfigurableListableBeanFactory beanFactory) {
+			return initialization -> initialization.contribute(code -> code.add("// Test\n"));
+		}
+
+	}
+
 	static class NoOpAotContributingBeanFactoryPostProcessor implements AotContributingBeanFactoryPostProcessor {
 
 		@Override
@@ -352,4 +388,23 @@ class ApplicationContextAotGeneratorTests {
 
 	}
 
+	static class TestSpringFactoriesClassLoader extends ClassLoader {
+
+		private final String factoriesName;
+
+		TestSpringFactoriesClassLoader(String factoriesName) {
+			super(RuntimeHintsPostProcessorTests.class.getClassLoader());
+			this.factoriesName = factoriesName;
+		}
+
+		@Override
+		public Enumeration<URL> getResources(String name) throws IOException {
+			if ("META-INF/spring.factories".equals(name)) {
+				return super.getResources("org/springframework/context/generator/aot/" + this.factoriesName);
+			}
+			return super.getResources(name);
+		}
+
+	}
+
 }

spring-context/src/test/resources/org/springframework/context/generator/aot/bean-factory-contributors.factories

@@ -0,0 +1,3 @@
+org.springframework.beans.factory.generator.AotContributingBeanFactoryPostProcessor= \
+org.springframework.context.generator.ApplicationContextAotGeneratorTests.NoOpAotContributingBeanFactoryPostProcessor, \
+org.springframework.context.generator.ApplicationContextAotGeneratorTests.TextAotContributingBeanFactoryPostProcessor