Add AOT support for immutable ConfigurationProperties bean definitions

This commit introduces a dedicated AotProcessors for immutable
configuration properties beans as their bean definition use an
instance supplier that needs special handling. If such a bean definition
is detected, dedicated code is generated that replicates the behavior
of the instance supplier.

Closes gh-31247

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBeanRegistrar.java

@@ -93,20 +93,10 @@ final class ConfigurationPropertiesBeanRegistrar {
 		RootBeanDefinition definition = new RootBeanDefinition(type);
 		definition.setAttribute(BindMethod.class.getName(), bindMethod);
 		if (bindMethod == BindMethod.VALUE_OBJECT) {
-			definition.setInstanceSupplier(() -> createValueObject(beanName, type));
+			definition.setInstanceSupplier(
+					() -> ConstructorBindingValueSupplier.createValueObject(this.beanFactory, beanName, type));
 		}
 		return definition;
 	}
 
-	private Object createValueObject(String beanName, Class<?> beanType) {
-		ConfigurationPropertiesBean bean = ConfigurationPropertiesBean.forValueObject(beanType, beanName);
-		ConfigurationPropertiesBinder binder = ConfigurationPropertiesBinder.get(this.beanFactory);
-		try {
-			return binder.bindOrCreate(bean);
-		}
-		catch (Exception ex) {
-			throw new ConfigurationPropertiesBindException(bean, ex);
-		}
-	}
-
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBeanRegistrationAotProcessor.java

@@ -0,0 +1,95 @@
+/*
+ * 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.context.properties;
+
+import java.lang.reflect.Executable;
+
+import javax.lang.model.element.Modifier;
+
+import org.springframework.aot.generate.GeneratedMethod;
+import org.springframework.aot.generate.GenerationContext;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.aot.BeanRegistrationAotContribution;
+import org.springframework.beans.factory.aot.BeanRegistrationAotProcessor;
+import org.springframework.beans.factory.aot.BeanRegistrationCode;
+import org.springframework.beans.factory.aot.BeanRegistrationCodeFragments;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.support.InstanceSupplier;
+import org.springframework.beans.factory.support.RegisteredBean;
+import org.springframework.boot.context.properties.ConfigurationPropertiesBean.BindMethod;
+import org.springframework.javapoet.CodeBlock;
+
+/**
+ * {@link BeanRegistrationAotProcessor} for immutable configuration properties.
+ *
+ * @author Stephane Nicoll
+ * @see ConstructorBindingValueSupplier
+ */
+class ConfigurationPropertiesBeanRegistrationAotProcessor implements BeanRegistrationAotProcessor {
+
+	@Override
+	public BeanRegistrationAotContribution processAheadOfTime(RegisteredBean registeredBean) {
+		if (!isImmutableConfigurationPropertiesBeanDefinition(registeredBean.getMergedBeanDefinition())) {
+			return null;
+		}
+		return BeanRegistrationAotContribution.ofBeanRegistrationCodeFragmentsCustomizer(
+				(codeFragments) -> new ConfigurationPropertiesBeanRegistrationCodeFragments(codeFragments,
+						registeredBean));
+
+	}
+
+	private boolean isImmutableConfigurationPropertiesBeanDefinition(BeanDefinition beanDefinition) {
+		return beanDefinition.hasAttribute(BindMethod.class.getName())
+				&& BindMethod.VALUE_OBJECT.equals(beanDefinition.getAttribute(BindMethod.class.getName()));
+	}
+
+	private static class ConfigurationPropertiesBeanRegistrationCodeFragments extends BeanRegistrationCodeFragments {
+
+		private static final String REGISTERED_BEAN_PARAMETER_NAME = "registeredBean";
+
+		private final RegisteredBean registeredBean;
+
+		ConfigurationPropertiesBeanRegistrationCodeFragments(BeanRegistrationCodeFragments codeFragments,
+				RegisteredBean registeredBean) {
+			super(codeFragments);
+			this.registeredBean = registeredBean;
+		}
+
+		@Override
+		public CodeBlock generateInstanceSupplierCode(GenerationContext generationContext,
+				BeanRegistrationCode beanRegistrationCode, Executable constructorOrFactoryMethod,
+				boolean allowDirectSupplierShortcut) {
+			GeneratedMethod method = beanRegistrationCode.getMethodGenerator().generateMethod("get", "instance")
+					.using((builder) -> {
+						Class<?> beanClass = this.registeredBean.getBeanClass();
+						builder.addJavadoc("Get the bean instance for '$L'.", this.registeredBean.getBeanName());
+						builder.addModifiers(Modifier.PRIVATE, Modifier.STATIC);
+						builder.returns(beanClass);
+						builder.addParameter(RegisteredBean.class, REGISTERED_BEAN_PARAMETER_NAME);
+						builder.addStatement("$T beanFactory = registeredBean.getBeanFactory()", BeanFactory.class);
+						builder.addStatement("$T beanName = registeredBean.getBeanName()", String.class);
+						builder.addStatement("$T<?> beanClass = registeredBean.getBeanClass()", Class.class);
+						builder.addStatement("return ($T) $T.createValueObject(beanFactory, beanName, beanClass)",
+								beanClass, ConstructorBindingValueSupplier.class);
+					});
+			return CodeBlock.of("$T.of($T::$L)", InstanceSupplier.class, beanRegistrationCode.getClassName(),
+					method.getName());
+		}
+
+	}
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConstructorBindingValueSupplier.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2019-2021 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.context.properties;
+
+import org.springframework.beans.factory.BeanFactory;
+
+/**
+ * Helper class to programmatically bind configuration properties that use constructor
+ * injection.
+ *
+ * @author Stephane Nicoll
+ * @since 6.0
+ * @see ConstructorBinding
+ */
+public abstract class ConstructorBindingValueSupplier {
+
+	/**
+	 * Return an immutable {@link ConfigurationProperties} instance for the specified
+	 * {@code beanType}.
+	 * @param beanFactory the bean factory to use
+	 * @param beanName the name of the bean
+	 * @param beanType the type of the bean
+	 * @return a new instance
+	 */
+	public static Object createValueObject(BeanFactory beanFactory, String beanName, Class<?> beanType) {
+		ConfigurationPropertiesBean bean = ConfigurationPropertiesBean.forValueObject(beanType, beanName);
+		ConfigurationPropertiesBinder binder = ConfigurationPropertiesBinder.get(beanFactory);
+		try {
+			return binder.bindOrCreate(bean);
+		}
+		catch (Exception ex) {
+			throw new ConfigurationPropertiesBindException(bean, ex);
+		}
+	}
+
+}

spring-boot-project/spring-boot/src/main/resources/META-INF/spring/aot.factories

@@ -2,4 +2,7 @@ org.springframework.aot.hint.RuntimeHintsRegistrar=\
 org.springframework.boot.logging.logback.LogbackRuntimeHintsRegistrar,\
 org.springframework.boot.WebApplicationType.WebApplicationTypeRuntimeHintsRegistrar
 org.springframework.beans.factory.aot.BeanFactoryInitializationAotProcessor=\
-org.springframework.boot.context.properties.ConfigurationPropertiesBeanFactoryInitializationAotProcessor
+org.springframework.boot.context.properties.ConfigurationPropertiesBeanFactoryInitializationAotProcessor
+
+org.springframework.beans.factory.aot.BeanRegistrationAotProcessor=\
+org.springframework.boot.context.properties.ConfigurationPropertiesBeanRegistrationAotProcessor

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBeanRegistrationAotProcessorTests.java

@@ -0,0 +1,102 @@
+/*
+ * 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.context.properties;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.aot.AotFactoriesLoader;
+import org.springframework.beans.factory.aot.BeanRegistrationAotContribution;
+import org.springframework.beans.factory.aot.BeanRegistrationAotProcessor;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.beans.factory.support.RegisteredBean;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConfigurationPropertiesBeanRegistrationAotProcessor}.
+ *
+ * @author Stephane Nicoll
+ */
+class ConfigurationPropertiesBeanRegistrationAotProcessorTests {
+
+	private final DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+
+	private final ConfigurationPropertiesBeanRegistrationAotProcessor processor = new ConfigurationPropertiesBeanRegistrationAotProcessor();
+
+	@Test
+	void configurationPropertiesBeanRegistrationAotProcessorIsRegistered() {
+		assertThat(new AotFactoriesLoader(new DefaultListableBeanFactory()).load(BeanRegistrationAotProcessor.class))
+				.anyMatch(ConfigurationPropertiesBeanRegistrationAotProcessor.class::isInstance);
+	}
+
+	@Test
+	void processAheadOfTimeWithNoConfigurationPropertiesBean() {
+		RootBeanDefinition beanDefinition = new RootBeanDefinition(String.class);
+		this.beanFactory.registerBeanDefinition("test", beanDefinition);
+		BeanRegistrationAotContribution contribution = this.processor
+				.processAheadOfTime(RegisteredBean.of(this.beanFactory, "test"));
+		assertThat(contribution).isNull();
+	}
+
+	@Test
+	void processAheadOfTimeWithJavaBeanConfigurationPropertiesBean() {
+		BeanRegistrationAotContribution contribution = process(JavaBeanSampleBean.class);
+		assertThat(contribution).isNull();
+	}
+
+	@Test
+	void processAheadOfTimeWithValueObjectConfigurationPropertiesBean() {
+		BeanRegistrationAotContribution contribution = process(ValueObjectSampleBean.class);
+		assertThat(contribution).isNotNull();
+	}
+
+	private BeanRegistrationAotContribution process(Class<?> type) {
+		ConfigurationPropertiesBeanRegistrar beanRegistrar = new ConfigurationPropertiesBeanRegistrar(this.beanFactory);
+		beanRegistrar.register(type);
+		RegisteredBean registeredBean = RegisteredBean.of(this.beanFactory,
+				this.beanFactory.getBeanDefinitionNames()[0]);
+		return this.processor.processAheadOfTime(registeredBean);
+	}
+
+	@ConfigurationProperties("test")
+	public static class JavaBeanSampleBean {
+
+		private String name;
+
+		public String getName() {
+			return this.name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+
+	}
+
+	@ConfigurationProperties("test")
+	public static class ValueObjectSampleBean {
+
+		private final String name;
+
+		ValueObjectSampleBean(String name) {
+			this.name = name;
+		}
+
+	}
+
+}