通过 @SpringBootApplication 注解导入
@SpringBootConfiguration @EnableAutoConfiguration @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) }) public @interface SpringBootApplication {
通过 @EnableAutoConfiguration 注解
@AutoConfigurationPackage @Import(AutoConfigurationImportSelector.class) public @interface EnableAutoConfiguration {
org.springframework.boot.autoconfigure.AutoConfigurationImportSelector
protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) { if (!isEnabled(annotationMetadata)) { return EMPTY_ENTRY; } AnnotationAttributes attributes = getAttributes(annotationMetadata); List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes); // 过滤掉重复的 configurations = removeDuplicates(configurations); Set<String> exclusions = getExclusions(annotationMetadata, attributes); checkExcludedClasses(configurations, exclusions); // 删掉排除的 configurations.removeAll(exclusions); // 过滤掉不用配置的 configurations = getConfigurationClassFilter().filter(configurations); fireAutoConfigurationImportEvents(configurations, exclusions); return new AutoConfigurationEntry(configurations, exclusions); }
spring 加载自动配置类依靠的是 SpringFactoriesLoader 类，该类会自动加载 ClassLoader 下所有 jar 包中的 META-INF/spring.factories 文件所配置的 Bean，类似于 JDK 的 SPI 机制
public final class SpringFactoriesLoader { public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories"; private static final Log logger = LogFactory.getLog(org.springframework.core.io.support.SpringFactoriesLoader.class); private static final Map<ClassLoader, MultiValueMap<String, String>> cache = new ConcurrentReferenceHashMap<>(); public static <T> List<T> loadFactories(Class<T> factoryType, @Nullable ClassLoader classLoader) { Assert.notNull(factoryType, "'factoryType' must not be null"); ClassLoader classLoaderToUse = classLoader; if (classLoaderToUse == null) { classLoaderToUse = org.springframework.core.io.support.SpringFactoriesLoader.class.getClassLoader(); } List<String> factoryImplementationNames = loadFactoryNames(factoryType, classLoaderToUse); if (logger.isTraceEnabled()) { logger.trace("Loaded [" + factoryType.getName() + "] names: " + factoryImplementationNames); } List<T> result = new ArrayList<>(factoryImplementationNames.size()); for (String factoryImplementationName : factoryImplementationNames) { result.add(instantiateFactory(factoryImplementationName, factoryType, classLoaderToUse)); } AnnotationAwareOrderComparator.sort(result); return result; } public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) { String factoryTypeName = factoryType.getName(); return loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList()); } private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) { MultiValueMap<String, String> result = cache.get(classLoader); if (result != null) { return result; } try { // 加载文件 Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)); result = new LinkedMultiValueMap<>(); while (urls.hasMoreElements()) { URL url = urls.nextElement(); UrlResource resource = new UrlResource(url); Properties properties = PropertiesLoaderUtils.loadProperties(resource); for (Map.Entry<?, ?> entry : properties.entrySet()) { String factoryTypeName = ((String) entry.getKey()).trim(); for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) { result.add(factoryTypeName, factoryImplementationName.trim()); } } } cache.put(classLoader, result); return result; } catch (IOException ex) { throw new IllegalArgumentException("Unable to load factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex); } } @SuppressWarnings("unchecked") private static <T> T instantiateFactory(String factoryImplementationName, Class<T> factoryType, ClassLoader classLoader) { try { Class<?> factoryImplementationClass = ClassUtils.forName(factoryImplementationName, classLoader); if (!factoryType.isAssignableFrom(factoryImplementationClass)) { throw new IllegalArgumentException("Class [" + factoryImplementationName + "] is not assignable to factory type [" + factoryType.getName() + "]"); } return (T) ReflectionUtils.accessibleConstructor(factoryImplementationClass).newInstance(); } catch (Throwable ex) { throw new IllegalArgumentException("Unable to instantiate factory class [" + factoryImplementationName + "] for factory type [" + factoryType.getName() + "]", ex); } } }
spring-boot-autoconfigure 包中的 spring.factories(部分) 文件
# Initializers org.springframework.context.ApplicationContextInitializer= org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer, org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener # Application Listeners org.springframework.context.ApplicationListener= org.springframework.boot.autoconfigure.BackgroundPreinitializer # Auto Configuration Import Listeners org.springframework.boot.autoconfigure.AutoConfigurationImportListener= org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener # Auto Configuration Import Filters org.springframework.boot.autoconfigure.AutoConfigurationImportFilter= org.springframework.boot.autoconfigure.condition.OnBeanCondition, org.springframework.boot.autoconfigure.condition.OnClassCondition # Auto Configure org.springframework.boot.autoconfigure.EnableAutoConfiguration= org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration, org.springframework.boot.autoconfigure.aop.AopAutoConfiguration # Failure analyzers org.springframework.boot.diagnostics.FailureAnalyzer= org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer, org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer # Template availability providers org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider= org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider, org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider
获取全部
获取 EnableAutoConfiguration 对应的
