Add basic support for parsing the bean definitions at build time

spring-aot/.gitignore

@@ -2,8 +2,8 @@ HELP.md
 cache/
 target/
 !.mvn/wrapper/maven-wrapper.jar
-!**/src/main/**
-!**/src/test/**
+!**/src/main/**/build/
+!**/src/test/**/build/
 hs_err_pid*
 
 ### STS ###
@@ -28,7 +28,6 @@ hs_err_pid*
 /dist/
 /nbdist/
 /.nb-gradle/
-build/
 
 ### VS Code ###
 .vscode/

spring-aot/pom.xml

@@ -24,6 +24,10 @@
 			<groupId>org.springframework</groupId>
 			<artifactId>spring-core</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-context</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-loader-tools</artifactId>

spring-aot/src/main/java/org/springframework/context/annotation/AnnotatedMetadataGenericBeanDefinition.java

@@ -0,0 +1,39 @@
+package org.springframework.context.annotation;
+
+import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
+import org.springframework.beans.factory.support.GenericBeanDefinition;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.core.type.MethodMetadata;
+import org.springframework.core.type.classreading.MetadataReader;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * A {@link GenericBeanDefinition} that also provides the {@link AnnotatedBeanDefinition}
+ * contract using ASM only.
+ *
+ * @author Stephane Nicoll
+ */
+public class AnnotatedMetadataGenericBeanDefinition extends GenericBeanDefinition implements AnnotatedBeanDefinition {
+
+	private final AnnotationMetadata metadata;
+
+	public AnnotatedMetadataGenericBeanDefinition(MetadataReader metadataReader) {
+		Assert.notNull(metadataReader, "MetadataReader must not be null");
+		this.metadata = metadataReader.getAnnotationMetadata();
+		setBeanClassName(this.metadata.getClassName());
+		setResource(metadataReader.getResource());
+	}
+
+	@Override
+	public final AnnotationMetadata getMetadata() {
+		return this.metadata;
+	}
+
+	@Override
+	@Nullable
+	public MethodMetadata getFactoryMethodMetadata() {
+		return null;
+	}
+
+}

spring-aot/src/main/java/org/springframework/context/build/BuildTimeBeanFactoryProvider.java

@@ -0,0 +1,91 @@
+package org.springframework.context.build;
+
+import java.io.IOException;
+
+import org.springframework.beans.factory.BeanDefinitionStoreException;
+import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
+import org.springframework.beans.factory.config.BeanDefinitionHolder;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
+import org.springframework.beans.factory.support.BeanNameGenerator;
+import org.springframework.context.annotation.AnnotatedMetadataGenericBeanDefinition;
+import org.springframework.context.annotation.AnnotationBeanNameGenerator;
+import org.springframework.context.annotation.ConfigurationClassPostProcessor;
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.core.type.classreading.MetadataReader;
+import org.springframework.core.type.classreading.MetadataReaderFactory;
+import org.springframework.core.type.classreading.SimpleMetadataReaderFactory;
+import org.springframework.core.type.classreading.TypeDescriptor;
+import org.springframework.core.type.classreading.TypeSystem;
+
+/**
+ * A prototype of {@link GenericApplicationContext} that is intended to be used at build
+ * time.
+ *
+ * @author Stephane Nicoll
+ */
+public class BuildTimeBeanFactoryProvider {
+
+	private final GenericApplicationContext context;
+
+	private final TypeSystem typeSystem;
+
+	private final MetadataReaderFactory metadataReaderFactory;
+
+	private final BeanNameGenerator beanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;
+
+	public BuildTimeBeanFactoryProvider(GenericApplicationContext context, TypeSystem typeSystem) {
+		this.context = context;
+		this.typeSystem = typeSystem;
+		this.metadataReaderFactory = new SimpleMetadataReaderFactory();
+	}
+
+	/**
+	 * Register root component classes that are meant to bootstrap the context.
+	 * @param componentClasses the root component classes
+	 */
+	public void register(String... componentClasses) {
+		for (String componentClass : componentClasses) {
+			TypeDescriptor componentTypeDescriptor = this.typeSystem.resolve(componentClass);
+			if (componentTypeDescriptor != null) {
+				register(componentTypeDescriptor);
+			}
+		}
+	}
+
+	/**
+	 * Process bean definitions without creating any instance and return the
+	 * {@link ConfigurableListableBeanFactory bean factory}.
+	 * @return the bean factory with the result of the processing
+	 */
+	public ConfigurableListableBeanFactory processBeanDefinitions() {
+		parseConfigurationClasses();
+		return this.context.getBeanFactory();
+	}
+
+	private void parseConfigurationClasses() {
+		ConfigurationClassPostProcessor configurationClassPostProcessor = new ConfigurationClassPostProcessor();
+		configurationClassPostProcessor.setApplicationStartup(this.context.getApplicationStartup());
+		configurationClassPostProcessor.setBeanClassLoader(this.context.getClassLoader());
+		configurationClassPostProcessor.setEnvironment(this.context.getEnvironment());
+		configurationClassPostProcessor.setResourceLoader(this.context);
+		configurationClassPostProcessor.postProcessBeanFactory(this.context.getBeanFactory());
+	}
+
+	private void register(TypeDescriptor typeDescriptor) {
+		MetadataReader metadataReader = getMetadataReader(typeDescriptor);
+		AnnotatedBeanDefinition beanDefinition = new AnnotatedMetadataGenericBeanDefinition(metadataReader);
+		String beanName = this.beanNameGenerator.generateBeanName(beanDefinition, this.context);
+		BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(beanDefinition, beanName);
+		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.context);
+	}
+
+	private MetadataReader getMetadataReader(TypeDescriptor typeDescriptor) {
+		try {
+			return this.metadataReaderFactory.getMetadataReader(typeDescriptor.getTypeName());
+		}
+		catch (IOException ex) {
+			throw new BeanDefinitionStoreException(String.format("Failure while reading metadata for %s.", typeDescriptor), ex);
+		}
+	}
+}

spring-aot/src/test/java/org/springframework/context/build/BuildTimeBeanFactoryProviderTests.java

@@ -0,0 +1,47 @@
+package org.springframework.context.build;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.type.classreading.TypeSystem;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link BuildTimeBeanFactoryProvider}.
+ *
+ * @author Stephane Nicoll
+ */
+class BuildTimeBeanFactoryProviderTests {
+
+	private static final String CONFIGURATION_ONE = "org.springframework.context.build.samples.simple.ConfigurationOne";
+
+	private static final String CONFIGURATION_TWO = "org.springframework.context.build.samples.simple.ConfigurationTwo";
+
+	private final TypeSystem typeSystem = TypeSystem.getTypeSystem(new DefaultResourceLoader());
+
+	@Test
+	void refreshWithRegisteredConfigurationClasses() {
+		BuildTimeBeanFactoryProvider beanFactoryProvider = forApplicationContext(new GenericApplicationContext());
+		beanFactoryProvider.register(CONFIGURATION_ONE, CONFIGURATION_TWO);
+		ConfigurableListableBeanFactory beanFactory = beanFactoryProvider.processBeanDefinitions();
+		assertThat(beanFactory.getBeanDefinitionNames()).containsOnly("configurationOne",
+				"configurationTwo", "beanOne", "beanTwo");
+	}
+
+	@Test
+	void refreshWithRegisteredConfigurationClassWithImport() {
+		BuildTimeBeanFactoryProvider context = forApplicationContext(new GenericApplicationContext());
+		context.register("org.springframework.context.build.samples.compose.ImportConfiguration");
+		ConfigurableListableBeanFactory beanFactory = context.processBeanDefinitions();
+		assertThat(beanFactory.getBeanDefinitionNames()).containsOnly("importConfiguration",
+				CONFIGURATION_ONE, CONFIGURATION_TWO, "beanOne", "beanTwo");
+	}
+
+	private BuildTimeBeanFactoryProvider forApplicationContext(GenericApplicationContext context) {
+		return new BuildTimeBeanFactoryProvider(context, this.typeSystem);
+	}
+
+}

spring-aot/src/test/java/org/springframework/context/build/samples/compose/ImportConfiguration.java

@@ -0,0 +1,11 @@
+package org.springframework.context.build.samples.compose;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.build.samples.simple.ConfigurationOne;
+import org.springframework.context.build.samples.simple.ConfigurationTwo;
+
+@Configuration(proxyBeanMethods = false)
+@Import({ ConfigurationOne.class, ConfigurationTwo.class })
+public class ImportConfiguration {
+}

spring-aot/src/test/java/org/springframework/context/build/samples/simple/ConfigurationOne.java

@@ -0,0 +1,14 @@
+package org.springframework.context.build.samples.simple;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration(proxyBeanMethods = false)
+public class ConfigurationOne {
+
+	@Bean
+	String beanOne() {
+		return "one";
+	}
+
+}

spring-aot/src/test/java/org/springframework/context/build/samples/simple/ConfigurationTwo.java

@@ -0,0 +1,14 @@
+package org.springframework.context.build.samples.simple;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration(proxyBeanMethods = false)
+public class ConfigurationTwo {
+
+	@Bean
+	String beanTwo() {
+		return "two";
+	}
+
+}

spring-aot/src/test/java/org/springframework/context/build/samples/simple/SimpleComponent.java

@@ -0,0 +1,8 @@
+package org.springframework.context.build.samples.simple;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class SimpleComponent {
+
+}