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springboot

2022-08-08 15:31:26   10  举报

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spring boot启动组件加载过程

Spring

SpringBoot

作者其他创作

大纲/内容

@SpringBootApplication

@SpringBootConfiguration

@EnableAutoConfiguration

@AutoConfigurationPackage

@Import({Registrar.class})

abstract class AutoConfigurationPackages { public static void register(BeanDefinitionRegistry registry, String... packageNames) {         if (registry.containsBeanDefinition(BEAN)) {             BeanDefinition beanDefinition = registry.getBeanDefinition(BEAN);             ConstructorArgumentValues constructorArguments = beanDefinition.getConstructorArgumentValues();             constructorArguments.addIndexedArgumentValue(0, addBasePackages(constructorArguments, packageNames));         } else {             GenericBeanDefinition beanDefinition = new GenericBeanDefinition();             beanDefinition.setBeanClass(AutoConfigurationPackages.BasePackages.class);             beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(0, packageNames);             beanDefinition.setRole(2);             registry.registerBeanDefinition(BEAN, beanDefinition);         }     } static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {         Registrar() {         }         public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {                                                                                                                                                //main Application所在包             AutoConfigurationPackages.register(registry, (new AutoConfigurationPackages.PackageImport(metadata)).getPackageName());         }         public Set<Object> determineImports(AnnotationMetadata metadata) {             return Collections.singleton(new AutoConfigurationPackages.PackageImport(metadata));         }     } }

@Import({AutoConfigurationImportSelector.class})

AutoConfigurationImportSelector{ public String[] selectImports(AnnotationMetadata annotationMetadata) {         if (!this.isEnabled(annotationMetadata)) {             return NO_IMPORTS;         } else {             AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);             AnnotationAttributes attributes = this.getAttributes(annotationMetadata);             List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);             configurations = this.removeDuplicates(configurations);             Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);             this.checkExcludedClasses(configurations, exclusions);             configurations.removeAll(exclusions);             configurations = this.filter(configurations, autoConfigurationMetadata);             this.fireAutoConfigurationImportEvents(configurations, exclusions);             return StringUtils.toStringArray(configurations);         }     } protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {         List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());         Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");         return configurations;     } }

abstract class SpringFactoriesLoader{ public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories"; public static List<String> loadFactoryNames(Class<?> factoryClass, @Nullable ClassLoader classLoader) {         String factoryClassName = factoryClass.getName();         return (List)loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList());     } private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {         MultiValueMap<String, String> result = (MultiValueMap)cache.get(classLoader);         if (result != null) {             return result;         } else {             try {                 Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");                 LinkedMultiValueMap result = new LinkedMultiValueMap();                 while(urls.hasMoreElements()) {                     URL url = (URL)urls.nextElement();                     UrlResource resource = new UrlResource(url);                     Properties properties = PropertiesLoaderUtils.loadProperties(resource);                     Iterator var6 = properties.entrySet().iterator();                     while(var6.hasNext()) {                         Entry<?, ?> entry = (Entry)var6.next();                         List<String> factoryClassNames = Arrays.asList(StringUtils.commaDelimitedListToStringArray((String)entry.getValue()));                         result.addAll((String)entry.getKey(), factoryClassNames);                     }                 }                 cache.put(classLoader, result);                 return result;             } catch (IOException var9) {                 throw new IllegalArgumentException("Unable to load factories from location [META-INF/spring.factories]", var9);             }         }     } }

@ComponentScan

Full @Configuration

如果@Bean方法在使用@Configuration注解的类中声明时称之为Full @Configuration

@Bean方法会被CGLIB所代理

被CGLIB的方法是不能被声明为private和final， 因为CGLIB是通过生成子类来实现代理的，private和final方法是不能被子类Override的， 也就是说，Full @Configuration模式下，@Bean的方法是不能不能被声明为private和final，不然在启动时Spring会直接报错

lite @Bean mode

当@Bean方法在没有使用@Configuration注解的类中声明时称之为lite @Bean mode 例如在@Component的类中使用@Bean

@Bean方法不会被CGLIB代理