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东莞地产网站建设,jquery做的网站,律师网站建站,搜狗做网站怎么样在SpringBoot中#xff0c;EnableAutoConfiguration注解用于开启自动装配功能。 本文将详细分析该注解的工作流程。 EnableAutoConfiguration注解 启用SpringBoot自动装配功能#xff0c;尝试猜测和配置可能需要的组件Bean。 自动装配类通常是根据类路径和定义的Bean来应…在SpringBoot中EnableAutoConfiguration注解用于开启自动装配功能。 本文将详细分析该注解的工作流程。 EnableAutoConfiguration注解 启用SpringBoot自动装配功能尝试猜测和配置可能需要的组件Bean。 自动装配类通常是根据类路径和定义的Bean来应用的。例如如果类路径上有tomcat-embedded.jar那么可能需要一个TomcatServletWebServerFactory(除非已经定义了自己的Servlet WebServerFactory Bean)。 自动装配试图尽可能地智能化并将随着开发者定义自己的配置而取消自动装配相冲突的配置。开发者可以使用exclude()排除不想使用的配置也可以通过spring.autoconfig.exclude属性排除这些配置。自动装配总是在用户定义的Bean注册之后应用。 用EnableAutoConfiguration注解标注的类所在包具有特定的意义通常用作默认扫描的包。通常建议将EnableAutoConfiguration(如果没有使用SpringBootApplication注解)放在根包中以便可以搜索所有子包和类。 自动装配类是普通的Spring Configuration类使用SpringFactoriesLoader机制定位。通常使用Conditional方式装配最常用的是ConditionalOnClass和ConditionalOnMissingBean注解。 AutoConfigurationPackage Import(AutoConfigurationImportSelector.class) public interface EnableAutoConfiguration {/*** Exclude specific auto-configuration classes such that they will never be applied./Class?[] exclude() default {};/** Exclude specific auto-configuration class names such that they will never be* applied.* 当类路径下没有指定的类时可以使用这个属性指定排除的类*/String[] excludeName() default {}; }该注解Import了AutoConfigurationImportSelector类AutoConfigurationImportSelector类实现了DeferredImportSelector接口。 Import注解和DeferredImportSelector接口在之前的Spring Import注解源码分析中详细分析过此处在介绍它们只分析AutoConfigurationImportSelector的工作流程。 AutoConfigurationImportSelector类 DeferredImportSelector接口 A variation of ImportSelector that runs after all Configuration beans have been processed. This type of selector can be particularly useful when the selected imports are Conditional. Implementations can also extend the org.springframework.core.Ordered interface or use the org.springframework.core.annotation.Order annotation to indicate a precedence against other DeferredImportSelectors. Implementations may also provide an import group which can provide additional sorting and filtering logic across different selectors. AutoConfigurationGroup类 AutoConfigurationImportSelector的getImportGroup方法返回了AutoConfigurationGroup类。 private static class AutoConfigurationGroup implements DeferredImportSelector.Group, BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware {private final MapString, AnnotationMetadata entries new LinkedHashMap();private final ListAutoConfigurationEntry autoConfigurationEntries new ArrayList();// … 略Overridepublic void process(AnnotationMetadata annotationMetadata,DeferredImportSelector deferredImportSelector) {// AutoConfigurationEntry类使用List保存Configuration类AutoConfigurationEntry autoConfigurationEntry ((AutoConfigurationImportSelector) deferredImportSelector).getAutoConfigurationEntry(annotationMetadata);this.autoConfigurationEntries.add(autoConfigurationEntry);for (String importClassName : autoConfigurationEntry.getConfigurations()) {this.entries.putIfAbsent(importClassName, annotationMetadata);}}Overridepublic IterableEntry selectImports() {// 查找排除的配置类SetString allExclusions this.autoConfigurationEntries.stream().map(AutoConfigurationEntry::getExclusions).flatMap(Collection::stream).collect(Collectors.toSet());// 所有配置类SetString processedConfigurations this.autoConfigurationEntries.stream().map(AutoConfigurationEntry::getConfigurations).flatMap(Collection::stream).collect(Collectors.toCollection(LinkedHashSet::new));// 将排除的配置类移除掉processedConfigurations.removeAll(allExclusions);// 排序return sortAutoConfigurations(processedConfigurations, getAutoConfigurationMetadata()).stream().map((importClassName) - new Entry(this.entries.get(importClassName), importClassName)).collect(Collectors.toList());}// … 略 }从上面的代码可以看出查找自动装配类的逻辑在getAutoConfigurationEntry方法中。 getAutoConfigurationEntry方法 从META-INF/spring.factories文件解析EnableAutoConfiguration配置。 META-INF/spring.factories文件示例 protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {AnnotationAttributes attributes getAttributes(annotationMetadata);// 查找自动装配类ListString configurations getCandidateConfigurations(annotationMetadata, attributes);// 以下几行为查找排除类、过滤等操作configurations removeDuplicates(configurations);SetString exclusions getExclusions(annotationMetadata, attributes);checkExcludedClasses(configurations, exclusions);configurations.removeAll(exclusions);// 这里的Filter是从META-INF/spring.factories文件解析出来的configurations getConfigurationClassFilter().filter(configurations);// 触发事件fireAutoConfigurationImportEvents(configurations, exclusions);return new AutoConfigurationEntry(configurations, exclusions); }protected ListString getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {// 从META-INF/spring.factories文件查找EnableAutoConfiguration配置ListString configurations SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());return configurations; }SpringFactoriesLoader类loadFactoryNames方法 Load the fully qualified class names of factory implementations of the given type from “META-INF/spring.factories”, using the given class loader. public static ListString loadFactoryNames(Class? factoryType, ClassLoader classLoader) {String factoryTypeName factoryType.getName();return loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList()); }private static MapString, ListString loadSpringFactories(ClassLoader classLoader) {MultiValueMapString, String result cache.get(classLoader);if (result ! null) {return result;}try {// FACTORIES_RESOURCE_LOCATION META-INF/spring.factories// 从类路径下查找META-INF/spring.factories文件EnumerationURL 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);// 获取properties配置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());}}}// 把配置添加缓存cache.put(classLoader, result);return result;} catch (IOException ex) {throw new IllegalArgumentException(Unable to load factories from location [ FACTORIES_RESOURCE_LOCATION ], ex);} }