spring boot容器启动流程

作者：Eve Cole 更新时间：2025-07-03 15:32:01

一、前言

spring cloud大行其道的当下，如果不了解基本原理那么是很纠结的(看见的都是约定大于配置，但是原理呢？为什么要这么做？)。spring cloud是基于spring boot快速搭建的，今天咱们就看看spring boot容器启动流程。(本文不讲解如何快速启动spring boot，那些直接官方看即可，官网文档飞机票 )

二、容器启动

spring boot一般是指定容器启动main方法，然后以命令行方式启动Jar包，如下图：

@SpringBootApplicationpublic class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }

这里核心关注2个东西：

1.@SpringBootApplication注解

2. SpringApplication.run()静态方法

下面我们就分别探究这两块内容。

2.1 @SpringBootApplication注解

源码如下：

@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) }) public @interface SpringBootApplication {

核心注解：

@SpringBootConfiguration（实际就是个@Configuration）：表示这是一个JavaConfig配置类，可以在这个类中自定义bean,依赖关系等。-》这个是spring-boot特有的注解，常用到。

@EnableAutoConfiguration：借助@Import的帮助，将所有符合自动配置条件的bean定义加载到IoC容器（建议放在根包路径下，这样可以扫描子包和类）。-》这个需要详细深挖！

@ComponentScan：spring的自动扫描注解，可定义扫描范围，加载到IOC容器。-》这个不多说，spring的注解大家肯定眼熟

其中@EnableAutoConfiguration这个注解的源码：

@SuppressWarnings("deprecation") @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @AutoConfigurationPackage @Import(EnableAutoConfigurationImportSelector.class) public @interface EnableAutoConfiguration {

核心是一个EnableAutoConfigurationImportSelector类图如下：

核心方法在顶级接口 ImportSelector 的 selectImports（），源码如下：

@Override public String[] selectImports(AnnotationMetadata annotationMetadata) { if (!isEnabled(annotationMetadata)) { return NO_IMPORTS; } try { //1.从META-INF/spring-autoconfigure-metadata.properties文件中载入483条配置属性（有一些有默认值）， AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader  .loadMetadata(this.beanClassLoader); AnnotationAttributes attributes = getAttributes(annotationMetadata);//2.获取注解属性 List<String> configurations = getCandidateConfigurations(annotationMetadata,//3.获取97个自动配置类  attributes); configurations = removeDuplicates(configurations);//4.移除重复的 configurations = sort(configurations, autoConfigurationMetadata);//5.排序 Set<String> exclusions = getExclusions(annotationMetadata, attributes);//6.获取需要排除的 checkExcludedClasses(configurations, exclusions);//7.校验排除类 configurations.removeAll(exclusions);//8.删除所有需要排除的 configurations = filter(configurations, autoConfigurationMetadata);//9.过滤器OnClassCondition（注解中配置的当存在某类才生效） fireAutoConfigurationImportEvents(configurations, exclusions);//10.触发自动配置导入监听事件 return configurations.toArray(new String[configurations.size()]); } catch (IOException ex) { throw new IllegalStateException(ex); } }

这里注意3个核心方法：

1） loadMetadata 加载配置

其实就是用类加载器去加载： META-INF/spring-autoconfigure-metadata.properties （spring-boot-autoconfigure-1.5.9.RELEASE-sources.jar）文件中定义的配置，返回PropertiesAutoConfigurationMetadata（实现了AutoConfigurationMetadata接口，封装了属性的get set方法）

2） getCandidateConfigurations 获取默认支持的自动配置类名列表

自动配置灵魂方法， SpringFactoriesLoader.loadFactoryNames 从 META-INF/spring.factories （spring-boot-autoconfigure-1.5.9.RELEASE-sources.jar）文件中获取自动配置类key=EnableAutoConfiguration.class的配置。

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {//话说这里2个入参没啥用啊...谁来给我解释一下... List<String> configurations = SpringFactoriesLoader.loadFactoryNames(  getSpringFactoriesLoaderFactoryClass(), 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; } //返回的是EnableAutoConfiguration类 protected Class<?> getSpringFactoriesLoaderFactoryClass() { return EnableAutoConfiguration.class; }

实际获取了什么？ spring.factories 文件如下，实际获取了 # Auto Configure 自动配置模块的所有类。

# Initializersorg.springframework.context.ApplicationContextInitializer=/org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,/org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer# Application Listenersorg.springframework.context.ApplicationListener=/org.springframework.boot.autoconfigure.BackgroundPreinitializer# Auto Configuration Import Listenersorg.springframework.boot.autoconfigure.AutoConfigurationImportListener=/org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener# Auto Configuration Import Filtersorg.springframework.boot.autoconfigure.AutoConfigurationImportFilter=/org.springframework.boot.autoconfigure.condition.OnClassCondition# Auto Configure 这里就是全部的自动配置类org.springframework.boot.autoconfigure.EnableAutoConfiguration=/org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,/org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,/org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,/org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,/org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,/org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration,/org.springframework.boot.autoconfigure.cloud.CloudAutoConfiguration,/org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,/org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,/org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,/org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,/org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,/org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,/org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,/org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchAutoConfiguration,/org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,/org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.ldap.LdapDataAutoConfiguration,/org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,/org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,/org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,/org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,/org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,/org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,/org.springframework.boot.autoconfigure.elasticsearch.jest.JestAutoConfiguration,/org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,/org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,/org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,/org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,/org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,/org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,/org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,/org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,/org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,/org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,/org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,/org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,/org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,/org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,/org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,/org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,/org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,/org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,/org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,/org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,/org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,/org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,/org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,/org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,/org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,/org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,/org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,/org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,/org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,/org.springframework.boot.autoconfigure.mobile.DeviceResolverAutoConfiguration,/org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration,/org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,/org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,/org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,/org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,/org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,/org.springframework.boot.autoconfigure.reactor.ReactorAutoConfiguration,/org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,/org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,/org.springframework.boot.autoconfigure.security.FallbackWebSecurityAutoConfiguration,/org.springframework.boot.autoconfigure.security.oauth2.OAuth2AutoConfiguration,/org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,/org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,/org.springframework.boot.autoconfigure.social.SocialWebAutoConfiguration,/org.springframework.boot.autoconfigure.social.FacebookAutoConfiguration,/org.springframework.boot.autoconfigure.social.LinkedInAutoConfiguration,/org.springframework.boot.autoconfigure.social.TwitterAutoConfiguration,/org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,/org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,/org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,/org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,/org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,/org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration,/org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration,/org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration,/org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,/org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,/org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,/org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,/org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration,/org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,/org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,/org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,/org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration# Failure analyzersorg.springframework.boot.diagnostics.FailureAnalyzer=/org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,/org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,/org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer# Template availability providersorg.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=/org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,/org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,/org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,/org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,/org.springframework.boot.autoconfigure.web.JspTemplateAvailabilityProvider

3）filter过滤器根据 OnClassCondition 注解把不满足条件的过滤掉

private List<String> filter(List<String> configurations, AutoConfigurationMetadata autoConfigurationMetadata) { long startTime = System.nanoTime(); String[] candidates = configurations.toArray(new String[configurations.size()]); boolean[] skip = new boolean[candidates.length]; boolean skipped = false; //获取需要过滤的自动配置导入拦截器，spring.factories配置中就一个：org.springframework.boot.autoconfigure.condition.OnClassCondition for (AutoConfigurationImportFilter filter : getAutoConfigurationImportFilters()) { invokeAwareMethods(filter); boolean[] match = filter.match(candidates, autoConfigurationMetadata); for (int i = 0; i < match.length; i++) {  if (!match[i]) {  skip[i] = true;  skipped = true;  } } } if (!skipped) {//多条件只要有一个不匹配->skipped = true，全部匹配-》skipped = false->直接返回 return configurations; } List<String> result = new ArrayList<String>(candidates.length); for (int i = 0; i < candidates.length; i++) { if (!skip[i]) {//匹配-》不跳过-》添加进result  result.add(candidates[i]); } } if (logger.isTraceEnabled()) { int numberFiltered = configurations.size() - result.size(); logger.trace("Filtered " + numberFiltered + " auto configuration class in "  + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime)  + " ms"); } return new ArrayList<String>(result); }

2.2 SpringApplication .run()静态方法

SpringApplication.run

public ConfigurableApplicationContext run(String... args) { StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; FailureAnalyzers analyzers = null; configureHeadlessProperty(); SpringApplicationRunListeners listeners = getRunListeners(args);//1.获取监听器 listeners.starting();-->启动！ try { ApplicationArguments applicationArguments = new DefaultApplicationArguments(  args); ConfigurableEnvironment environment = prepareEnvironment(listeners,//2.准备好环境，触发ApplicationEnvironmentPreparedEvent事件  applicationArguments); Banner printedBanner = printBanner(environment);//打印启动提示字符，默认spring的字符图 context = createApplicationContext();//实例化一个可配置应用上下文 analyzers = new FailureAnalyzers(context); prepareContext(context, environment, listeners, applicationArguments,//3.准备上下文  printedBanner); refreshContext(context);//4.刷新上下文 afterRefresh(context, applicationArguments);//5.刷新上下文后 listeners.finished(context, null);--关闭！ stopWatch.stop(); if (this.logStartupInfo) {  new StartupInfoLogger(this.mainApplicationClass)  .logStarted(getApplicationLog(), stopWatch); } return context; } catch (Throwable ex) { handleRunFailure(context, listeners, analyzers, ex); throw new IllegalStateException(ex); } }

1. getRunListeners 获取监听器（ SpringApplicationRunListeners ）

实际是 SpringApplicationRunListener 类

private SpringApplicationRunListeners getRunListeners(String[] args) { Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class }; return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances( SpringApplicationRunListener.class, types, this, args)); } private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type) { return getSpringFactoriesInstances(type, new Class<?>[] {}); } private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) { ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); // 使用Set确保的字符串的唯一性 Set<String> names = new LinkedHashSet<String>( SpringFactoriesLoader.loadFactoryNames(type, classLoader));// 1.载入工厂名称集合 List<T> instances = createSpringFactoriesInstances(type, parameterTypes,// 2.创建工厂实例 classLoader, args, names); AnnotationAwareOrderComparator.sort(instances);// 排序 return instances; }

1.1 载入工厂名称（loadFactoryNames）

当前类的类加载器从 META-INF/spring.factories 文件中获取SpringApplicationRunListener类的配置

public static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) { String factoryClassName = factoryClass.getName(); try { Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :  ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)); List<String> result = new ArrayList<String>(); while (urls.hasMoreElements()) {  URL url = urls.nextElement();  Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));  String factoryClassNames = properties.getProperty(factoryClassName);  result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames))); } return result; } catch (IOException ex) { throw new IllegalArgumentException("Unable to load [" + factoryClass.getName() +  "] factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex); } }

上图，获取到工厂类名后，下面来看看META-INF/spring.factories中定义了啥：

# PropertySource Loadersorg.springframework.boot.env.PropertySourceLoader=/org.springframework.boot.env.PropertiesPropertySourceLoader,/org.springframework.boot.env.YamlPropertySourceLoader# Run Listeners 这里呢，看这里！！！！org.springframework.boot.SpringApplicationRunListener=/org.springframework.boot.context.event.EventPublishingRunListener# Application Context Initializersorg.springframework.context.ApplicationContextInitializer=/org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,/org.springframework.boot.context.ContextIdApplicationContextInitializer,/org.springframework.boot.context.config.DelegatingApplicationContextInitializer,/org.springframework.boot.context.embedded.ServerPortInfoApplicationContextInitializer# Application Listenersorg.springframework.context.ApplicationListener=/org.springframework.boot.ClearCachesApplicationListener,/org.springframework.boot.builder.ParentContextCloserApplicationListener,/org.springframework.boot.context.FileEncodingApplicationListener,/org.springframework.boot.context.config.AnsiOutputApplicationListener,/org.springframework.boot.context.config.ConfigFileApplicationListener,/org.springframework.boot.context.config.DelegatingApplicationListener,/org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener,/org.springframework.boot.logging.ClasspathLoggingApplicationListener,/org.springframework.boot.logging.LoggingApplicationListener# Environment Post Processorsorg.springframework.boot.env.EnvironmentPostProcessor=/org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,/org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor# Failure Analyzersorg.springframework.boot.diagnostics.FailureAnalyzer=/org.springframework.boot.diagnostics.analyzer.BeanCurrentlyInCreationFailureAnalyzer,/org.springframework.boot.diagnostics.analyzer.BeanNotOfRequiredTypeFailureAnalyzer,/org.springframework.boot.diagnostics.analyzer.BindFailureAnalyzer,/org.springframework.boot.diagnostics.analyzer.ConnectorStartFailureAnalyzer,/org.springframework.boot.diagnostics.analyzer.NoUniqueBeanDefinitionFailureAnalyzer,/org.springframework.boot.diagnostics.analyzer.PortInUseFailureAnalyzer,/org.springframework.boot.diagnostics.analyzer.ValidationExceptionFailureAnalyzer# FailureAnalysisReportersorg.springframework.boot.diagnostics.FailureAnalysisReporter=/org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter

哇，都是些类全名称，且key都是接口，value都是实现类。我们根据key=“ org.springframework.boot.SpringApplicationRunListener ”查询得到实现类value=" org.springframework.boot.context.event.EventPublishingRunListener" 事件发布启动监听器，一猜也知道肯定要用” 反射 ”根据类名获取类实例，下面很快得到验证...

1.2 创建spring工厂实例（createSpringFactoriesInstances）

根据第一步得到的Set<String> names（SpringApplicationRunListener的唯一实现类 EventPublishingRunListener ）生成" 事件发布启动监听器 " 工厂实例

@SuppressWarnings("unchecked") private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args, Set<String> names) { List<T> instances = new ArrayList<T>(names.size()); for (String name : names) { try {  Class<?> instanceClass = ClassUtils.forName(name, classLoader);// 利用反射获取类  Assert.isAssignable(type, instanceClass);  Constructor<?> constructor = instanceClass  .getDeclaredConstructor(parameterTypes);// 得到构造器  T instance = (T) BeanUtils.instantiateClass(constructor, args);// 根据构造器和参数构造实例  instances.add(instance); } catch (Throwable ex) {  throw new IllegalArgumentException(  "Cannot instantiate " + type + " : " + name, ex); } } return instances; }

准备上下文

private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) { context.setEnvironment(environment); postProcessApplicationContext(context);//单例一个BeanNameGenerator，把ResourceLoader设置进应用上下文 applyInitializers(context);//执行初始化器 listeners.contextPrepared(context);// 监听器执行上下文"已准备好"方法 if (this.logStartupInfo) { logStartupInfo(context.getParent() == null); logStartupProfileInfo(context); }  // 添加spring boot特殊单例bean context.getBeanFactory().registerSingleton("springApplicationArguments",  applicationArguments); if (printedBanner != null) { context.getBeanFactory().registerSingleton("springBootBanner", printedBanner); } // 载入资源 Set<Object> sources = getSources(); Assert.notEmpty(sources, "Sources must not be empty"); load(context, sources.toArray(new Object[sources.size()])); listeners.contextLoaded(context);// 监听器执行"上下文已加载"方法 }

刷新上下文

private void refreshContext(ConfigurableApplicationContext context) { refresh(context);//核心类 if (this.registerShutdownHook) { try { context.registerShutdownHook();//注册关闭钩子，容器关闭时执行 } catch (AccessControlException ex) { // Not allowed in some environments. } } } protected void refresh(ApplicationContext applicationContext) { Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext); ((AbstractApplicationContext) applicationContext).refresh(); }

最终执行的是AbstractApplicationContext抽象类的 refresh 方法。

public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { //准备刷新的上下文环境，例如对系统属性或者环境变量进行准备及验证。 prepareRefresh(); //启动子类的refreshBeanFactory方法.解析xml ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); //为BeanFactory配置容器特性，例如类加载器、事件处理器等. prepareBeanFactory(beanFactory); try {  //设置BeanFactory的后置处理. 空方法，留给子类拓展用。   postProcessBeanFactory(beanFactory);  //调用BeanFactory的后处理器, 这些后处理器是在Bean定义中向容器注册的.   invokeBeanFactoryPostProcessors(beanFactory);  //注册Bean的后处理器, 在Bean创建过程中调用.   registerBeanPostProcessors(beanFactory);  //初始化上下文中的消息源，即不同语言的消息体进行国际化处理   initMessageSource();  //初始化ApplicationEventMulticaster bean,应用事件广播器  initApplicationEventMulticaster();  //初始化其它特殊的Bean， 空方法，留给子类拓展用。   onRefresh();  //检查并向容器注册监听器Bean  registerListeners();  //实例化所有剩余的(non-lazy-init) 单例Bean.  finishBeanFactoryInitialization(beanFactory);  //发布容器事件, 结束refresh过程.   finishRefresh(); } catch (BeansException ex) {  if (logger.isWarnEnabled()) {  logger.warn("Exception encountered during context initialization - " +  "cancelling refresh attempt: " + ex);  }  //销毁已经创建的单例Bean, 以避免资源占用.  destroyBeans();  //取消refresh操作, 重置active标志.   cancelRefresh(ex);  // Propagate exception to caller.  throw ex; } finally {  //重置Spring的核心缓存  resetCommonCaches(); } } }

刷新完上下文后

spring boot提供的2个供用户自己拓展的接口： ApplicationRunner和 CommandLineRunner。可以在容器启动完毕后（上下文刷新后）执行，做一些类似数据初始化的操作。

private void callRunners(ApplicationContext context, ApplicationArguments args) { List<Object> runners = new ArrayList<Object>(); runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());//从上下文中获取ApplicationRunner类型的bean runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());//从上下文中获取CommandLineRunner类型的bean AnnotationAwareOrderComparator.sort(runners);//排序 for (Object runner : new LinkedHashSet<Object>(runners)) { if (runner instanceof ApplicationRunner) {  callRunner((ApplicationRunner) runner, args);//执行 } if (runner instanceof CommandLineRunner) {  callRunner((CommandLineRunner) runner, args); } } }

两个区别在于入参不同，根据实际情况自己选择。

public interface CommandLineRunner { void run(String... args) throws Exception; } public interface ApplicationRunner { void run(ApplicationArguments args) throws Exception; }

CommandLineRunner中执行参数是原始的 java启动类main方法的String[] args字符串数组参数； ApplicationRunner中的参数经过处理提供一些方法例如:

List<String> getOptionValues(String name);

根据名称获取值list,java 启动命令中 --foo=bar --foo=baz，则根据foo参数名返回list ["bar", "baz"]

三、总结

按照前面的分析，Spring-boot容器启动流程总体可划分为2部分：

1）执行注解：扫描指定范围下的bean、载入自动配置类对应的bean加载到IOC容器。

2）man方法中具体SpringAppliocation.run() ，全流程贯穿SpringApplicationEvent,有6个子类：

ApplicationFailedEvent.classApplicationPreparedEvent.classApplicationReadyEvent.classApplicationStartedEvent.classApplicationStartingEvent.classSpringApplicationEvent.class

这里用到了很经典的 spring事件驱动模型，飞机票： Spring事件驱动模型和观察者模式

类图如下：

如上图，就是一个经典spring 事件驱动模型，包含3种角色：事件发布者、事件、监听者。对应到spring-boot中就是：

1 .EventPublishingRunListener 这个类封装了事件发布，

2. SpringApplicationEvent 是spring-boot中定义的事件（上面说的6种事件），继承自 ApplicationEvent （spring中定义的）

3. 监听者 spring-boot并没有实现针对上述6种事件的监听者（我没找到...），这里用户可以自己实现监听者（上述6种事件）来注入spring boot容器启动流程，触发相应的事件。

例如：实现ApplicationListener<ApplicationReadyEvent>这个接口，在容器启动完毕时最后一步listener.finished时，如果启动没有异常，就会执行！可以做一些数据初始化之类的操作。

总结

以上所述是小编给大家介绍的spring boot容器启动的相关知识，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对武林网网站的支持！