最棒 Spring Boot 干貨總結(jié)（超詳細(xì)，建議收藏）
點(diǎn)擊上方“Java耕耘者”，星標(biāo)公眾號(hào)
說(shuō)明：前面有4個(gè)小節(jié)關(guān)于Spring的基礎(chǔ)知識(shí)
分別是：IOC容器、JavaConfig、事件監(jiān)聽(tīng)、SpringFactoriesLoader詳解
它們占據(jù)了本文的大部分內(nèi)容：
雖然它們之間可能沒(méi)有太多的聯(lián)系，但這些知識(shí)對(duì)于理解Spring Boot的核心原理至關(guān)重要，如果你對(duì)Spring框架爛熟于心，完全可以跳過(guò)這4個(gè)小節(jié)。正是因?yàn)檫@個(gè)系列的文章是由這些看似不相關(guān)的知識(shí)點(diǎn)組成，因此取名知識(shí)清單。
在過(guò)去兩三年的Spring生態(tài)圈，最讓人興奮的莫過(guò)于Spring Boot框架。或許從命名上就能看出這個(gè)框架的設(shè)計(jì)初衷：快速的啟動(dòng)Spring應(yīng)用。因而Spring Boot應(yīng)用本質(zhì)上就是一個(gè)基于Spring框架的應(yīng)用，它是Spring對(duì)“約定優(yōu)先于配置”理念的最佳實(shí)踐產(chǎn)物，它能夠幫助開(kāi)發(fā)者更快速高效地構(gòu)建基于Spring生態(tài)圈的應(yīng)用。
那Spring Boot有何魔法？
自動(dòng)配置、起步依賴(lài)、Actuator、命令行界面(CLI) 是Spring Boot最重要的4大核心特性，其中CLI是Spring Boot的可選特性，雖然它功能強(qiáng)大，但也引入了一套不太常規(guī)的開(kāi)發(fā)模型，因而這個(gè)系列的文章僅關(guān)注其它3種特性。如文章標(biāo)題，本文是這個(gè)系列的第一部分，將為你打開(kāi)Spring Boot的大門(mén)，重點(diǎn)為你剖析其啟動(dòng)流程以及自動(dòng)配置實(shí)現(xiàn)原理。要掌握這部分核心內(nèi)容，理解一些Spring框架的基礎(chǔ)知識(shí)，將會(huì)讓你事半功倍。
我把 Spring Boot 相關(guān)的文章整理成了 PDF，關(guān)注公眾號(hào) Java后端?并回復(fù) 666 下載。
一、拋磚引玉：探索Spring IoC容器
如果有看過(guò)SpringApplication.run()方法的源碼，Spring Boot冗長(zhǎng)無(wú)比的啟動(dòng)流程一定
會(huì)讓你抓狂，透過(guò)現(xiàn)象看本質(zhì).
SpringApplication只是將一個(gè)典型的Spring應(yīng)用的啟動(dòng)流程進(jìn)行了擴(kuò)展，因此，透徹理解,?Spring容器是打開(kāi)Spring Boot大門(mén)的一把鑰匙。
1.1、Spring IoC容器
可以把Spring IoC容器比作一間餐館，當(dāng)你來(lái)到餐館，通常會(huì)直接招呼服務(wù)員：點(diǎn)菜！至于菜的原料是什么？如何用原料把菜做出來(lái)？可能你根本就不關(guān)心。
IoC容器也是一樣，你只需要告訴它需要某個(gè)bean，它就把對(duì)應(yīng)的實(shí)例（instance）扔給你，至于這個(gè)bean是否依賴(lài)其他組件，怎樣完成它的初始化，根本就不需要你關(guān)心。
作為餐館，想要做出菜肴，得知道菜的原料和菜譜，同樣地，IoC容器想要管理各個(gè)業(yè)務(wù)對(duì)象以及它們之間的依賴(lài)關(guān)系，需要通過(guò)某種途徑來(lái)記錄和管理這些信息。
BeanDefinition對(duì)象就承擔(dān)了這個(gè)責(zé)任：容器中的每一個(gè)bean都會(huì)有一個(gè)對(duì)應(yīng)的BeanDefinition實(shí)例，該實(shí)例負(fù)責(zé)保存bean對(duì)象的所有必要信息，包括bean對(duì)象的class類(lèi)型、是否是抽象類(lèi)、構(gòu)造方法和參數(shù)、其它屬性等等。
當(dāng)客戶(hù)端向容器請(qǐng)求相應(yīng)對(duì)象時(shí)，容器就會(huì)通過(guò)這些信息為客戶(hù)端返回一個(gè)完整可用的bean實(shí)例。
原材料已經(jīng)準(zhǔn)備好（把BeanDefinition看著原料），開(kāi)始做菜吧，等等，你還需要一份菜譜，BeanDefinitionRegistry和BeanFactory就是這份菜譜，BeanDefinitionRegistry抽象出bean的注冊(cè)邏輯，而B(niǎo)eanFactory則抽象出了bean的管理邏輯，而各個(gè)BeanFactory的實(shí)現(xiàn)類(lèi)就具體承擔(dān)了bean的注冊(cè)以及管理工作。
它們之間的關(guān)系就如下圖：
BeanFactory、BeanDefinitionRegistry關(guān)系圖（來(lái)自：Spring揭秘）
DefaultListableBeanFactory作為一個(gè)比較通用的BeanFactory實(shí)現(xiàn)，它同時(shí)也實(shí)現(xiàn)了BeanDefinitionRegistry接口，因此它就承擔(dān)了Bean的注冊(cè)管理工作。從圖中也可以看出，BeanFactory接口中主要包含getBean、containBean、getType、getAliases等管理bean的方法，而B(niǎo)eanDefinitionRegistry接口則包含registerBeanDefinition、removeBeanDefinition、getBeanDefinition等注冊(cè)管理BeanDefinition的方法。
下面通過(guò)一段簡(jiǎn)單的代碼來(lái)模擬BeanFactory底層是如何工作的：
// 默認(rèn)容器實(shí)現(xiàn)
?DefaultListableBeanFactory beanRegistry = new?DefaultListableBeanFactory();
?// 根據(jù)業(yè)務(wù)對(duì)象構(gòu)造相應(yīng)的BeanDefinition
?AbstractBeanDefinition definition = new?RootBeanDefinition(Business.class,true);
?// 將bean定義注冊(cè)到容器中
?beanRegistry.registerBeanDefinition("beanName",definition);
?// 如果有多個(gè)bean，還可以指定各個(gè)bean之間的依賴(lài)關(guān)系
?// ........
??// 然后可以從容器中獲取這個(gè)bean的實(shí)例
?// 注意：這里的beanRegistry其實(shí)實(shí)現(xiàn)了BeanFactory接口，所以可以強(qiáng)轉(zhuǎn)，
?// 單純的BeanDefinitionRegistry是無(wú)法強(qiáng)制轉(zhuǎn)換到BeanFactory類(lèi)型的
?BeanFactory container = (BeanFactory)beanRegistry;
?Business business = (Business)container.getBean("beanName");// 通常為BeanDefinitionRegistry的實(shí)現(xiàn)類(lèi)，這里以DeFaultListabeBeanFactory為例
?BeanDefinitionRegistry beanRegistry = new?DefaultListableBeanFactory();
??// XmlBeanDefinitionReader實(shí)現(xiàn)了BeanDefinitionReader接口，用于解析XML文件
?XmlBeanDefinitionReader beanDefinitionReader = new?XmlBeanDefinitionReaderImpl(beanRegistry);
?// 加載配置文件 beanDefinitionReader.loadBeanDefinitions("classpath:spring-bean.xml");
??// 從容器中獲取bean實(shí)例
?BeanFactory container = (BeanFactory)beanRegistry;
?Business business = (Business)container.getBean("beanName");// 通常為BeanDefinitionRegistry的實(shí)現(xiàn)類(lèi)，這里以DeFaultListabeBeanFactory為例
?BeanDefinitionRegistry beanRegistry = new?DefaultListableBeanFactory();
??// XmlBeanDefinitionReader實(shí)現(xiàn)了BeanDefinitionReader接口，用于解析XML文件
?XmlBeanDefinitionReader beanDefinitionReader = new?XmlBeanDefinitionReaderImpl(beanRegistry);
?// 加載配置文件 beanDefinitionReader.loadBeanDefinitions("classpath:spring-bean.xml");
??// 從容器中獲取bean實(shí)例
?BeanFactory container = (BeanFactory)beanRegistry;
?Business business = (Business)container.getBean("beanName");
// 代碼來(lái)自：org.springframework.context.support.ApplicationContextAwareProcessor
?// 其postProcessBeforeInitialization方法調(diào)用了invokeAwareInterfaces方法
?private?void?invokeAwareInterfaces(Object?bean){
?????if?(bean instanceof?EnvironmentAware){
?????????((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
?????}
?????if?(bean instanceof?ApplicationContextAware){
?????????((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
?????}
?????// ......
}"bookService" ?class="cn.moondev.service.BookServiceImpl">bean>@Configuration
?public?class
?MoonBookConfiguration
?{
??????// 任何標(biāo)志了@Bean的方法，其返回值將作為一個(gè)bean注冊(cè)到Spring的IOC容器中
?????// 方法名默認(rèn)成為該bean定義的id
?????@Bean
?????public?BookService bookService()?{
?????????return?new?BookServiceImpl();
?????}
?}"bookService" ?class="cn.moondev.service.BookServiceImpl">
?????<property?name="dependencyService"?ref="dependencyService"/>
?bean>
??"otherService"?class="cn.moondev.service.OtherServiceImpl">
?????<property?name="dependencyService"?ref="dependencyService"/>
?bean>
??"dependencyService"?class="DependencyServiceImpl"/> @Configuration
?public?class?MoonBookConfiguration?{
??????// 如果一個(gè)bean依賴(lài)另一個(gè)bean，則直接調(diào)用對(duì)應(yīng)JavaConfig類(lèi)中依賴(lài)bean的創(chuàng)建方法即可
?????// 這里直接調(diào)用dependencyService()
?????@Bean
?????public?BookService bookService()?{
?????????return?new?BookServiceImpl(dependencyService());
?????}
??????@Bean
?????public?OtherService otherService()?{
?????????return?new?OtherServiceImpl(dependencyService());
?????}
??????@Bean
?????public?DependencyService dependencyService()?{
?????????return?new?DependencyServiceImpl();
?????}
?}@Configuration
?public?class?MoonBookConfiguration{
?????@Bean
?????public?BookService bookService()?{
?????????return?new?BookServiceImpl();
?????}
?}@Configuration
?// 可以同時(shí)導(dǎo)入多個(gè)配置類(lèi)，比如：@Import({A.class,B.class})
?@Import(MoonBookConfiguration.class)
?public class MoonUserConfiguration
?{
?????@Bean
?????public UserService userService(BookService bookService) {
?????????return?new?BookServiceImpl(bookService);
?????}
?}
public?class?JdbcTemplateCondition?implements?Condition?{
??????@Override
?????public?boolean?matches(ConditionContext
?conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata)?{
?????????try?{
?????????conditionContext.getClassLoader().loadClass("org.springframework.jdbc.core.JdbcTemplate");
?????????????return?true;
?????????}
?catch?(ClassNotFoundException e) {
?????????????e.printStackTrace();
?????????}
?????????return?false;
?????}
?}@Conditional(JdbcTemplateCondition.class) @Service?public MyService service() { ...... }
// jdbc config
?jdbc.mysql.url=jdbc:mysql://localhost:3306/sampledb
?jdbc.mysql.username=root
?jdbc.mysql.password=123456
?......
??// 配置數(shù)據(jù)源
?@Configuration
?public?class?HikariDataSourceConfiguration {
??????@Value("jdbc.mysql.url")
?????public?String?url;
?????@Value("jdbc.mysql.username")
?????public?String?user;
?????@Value("jdbc.mysql.password")
?????public?String?password;
??????????@Bean
?????public?HikariDataSource dataSource() {
?????????HikariConfig hikariConfig = new?HikariConfig();
?????????hikariConfig.setJdbcUrl(url);
?????????hikariConfig.setUsername(user);
?????????hikariConfig.setPassword(password);
?????????// 省略部分代碼
?????????return?new?HikariDataSource(hikariConfig);
?????}
?}@Component
?// 還可以通過(guò)@PropertySource("classpath:jdbc.properties")來(lái)指定配置文件
?@ConfigurationProperties("jdbc.mysql")
?// 前綴=jdbc.mysql，會(huì)在配置文件中尋找jdbc.mysql.*的配置項(xiàng)
?pulic class?JdbcConfig {
?????public?String?url;
?????public?String?username;
?????public?String?password;
?}
??@Configuration
?public?class?HikariDataSourceConfiguration {
??????@AutoWired
?????public?JdbcConfig config;
??????????@Bean
?????public?HikariDataSource dataSource() {
?????????HikariConfig hikariConfig = new?HikariConfig();
?????????hikariConfig.setJdbcUrl(config.url);
?????????hikariConfig.setUsername(config.username);
?????????hikariConfig.setPassword(config.password);
?????????// 省略部分代碼
?????????return?new?HikariDataSource(hikariConfig);
???}
?}#App
?app.menus[0].title=Home
?app.menus[0].name=Home
?app.menus[0].path=/
?app.menus[1].title=Login
?app.menus[1].name=Login
?app.menus[1].path=/login
??app.compiler.timeout=5
?app.compiler.output-folder=/temp/
??app.error=/error/@Component
?@ConfigurationProperties("app")
?public?class?AppProperties {
??????public?String?error;
?????public?Listprotected?Class loadClass(String?name, boolean?resolve) {
?????synchronized (getClassLoadingLock(name)) {
?????// 首先，檢查該類(lèi)是否已經(jīng)被加載，如果從JVM緩存中找到該類(lèi)，則直接返回
?????Class c = findLoadedClass(name);
?????if?(c == null) {
?????????try?{
?????????????// 遵循雙親委派的模型，首先會(huì)通過(guò)遞歸從父加載器開(kāi)始找，
?????????????// 直到父類(lèi)加載器是BootstrapClassLoader為止
?????????????if?(parent != null) {
?????????????????c = parent.loadClass(name, false);
?????????????} else?{
?????????????????c = findBootstrapClassOrNull(name);
?????????????}
????????} catch?(ClassNotFoundException e) {}
?????????if?(c == null) {
?????????????// 如果還找不到，嘗試通過(guò)findClass方法去尋找
?????????????// findClass是留給開(kāi)發(fā)者自己實(shí)現(xiàn)的，也就是說(shuō)
?????????????// 自定義類(lèi)加載器時(shí)，重寫(xiě)此方法即可
????????????c = findClass(name);
?????????}
?????}
?????if?(resolve) {
????????resolveClass(c);
?????}
?????return?c;
?????}
?}
for?(String?aDriver : driversList) {
?????try?{
?????????// 直接使用AppClassLoader
?????????Class.forName(aDriver, true, ClassLoader.getSystemClassLoader());
?????} catch?(Exception ex) {
?????????println("DriverManager.Initialize: load failed: "?+ ex);
??????}
???}Thread.currentThread().getClassLoader()Thread.currentThread().getContextClassLoader()public Enumeration<URL>?getResources(String name) throws IOException {
?????Enumeration<URL>[] tmp = (Enumeration<URL>[]) new Enumeration>[2];
?????if?(parent?!= null) {
?????????tmp[0] = parent.getResources(name);
?????} else?{
?????????tmp[0] = getBootstrapResources(name);
?????}
?????tmp[1] = findResources(name);
?????return?new?CompoundEnumeration<>(tmp);
?}// 尋找Array.class文件
?public?static?void?main(String[] args) throws Exception{
?????// Array.class的完整路徑
?????String name = "java/sql/Array.class";
?????Enumerationurls = Thread.currentThread().getContextClassLoader().getResources(name);
?????while?(urls.hasMoreElements()) {
?????????URL url = urls.nextElement();
?????????System.out.println(url.toString());
?????}
?} $JAVA_HOME/jre/lib/rt.jar!/java/sql/Array.classpublic?static?final String?FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
?// spring.factories文件的格式為：key=value1,value2,value3
?// 從所有的jar包中找到META-INF/spring.factories文件
?// 然后從文件中解析出key=factoryClass類(lèi)名稱(chēng)的所有value值
?public?static?List<String> loadFactoryNames(Class factoryClass, ClassLoader classLoader) {
?????String?factoryClassName = factoryClass.getName();
?????// 取得資源文件的URL
?????Enumerationurls = (classLoader != null?? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
?????List<String> result = new?ArrayList<String>();
?????// 遍歷所有的URL
?????while?(urls.hasMoreElements()) {
?????????URL url = urls.nextElement();
?????????// 根據(jù)資源文件URL解析properties文件
?????????Properties properties = PropertiesLoaderUtils.loadProperties(new?UrlResource(url));
?????????String?factoryClassNames = properties.getProperty(factoryClassName);
?????????// 組裝數(shù)據(jù)，并返回
?????????result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));
?????}
?????return?result;
?} // 來(lái)自 org.springframework.boot.autoconfigure下的META-INF/spring.factories
?// EnableAutoConfiguration后文會(huì)講到，它用于開(kāi)啟Spring Boot自動(dòng)配置功能
?org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
?org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
?org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
?org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration\public?class?MethodMonitorEvent?extends?EventObject?{
?????// 時(shí)間戳，用于記錄方法開(kāi)始執(zhí)行的時(shí)間
?????public?long?timest
??????public?MethodMonitorEvent(Object source)?{
?????????super(source);
?????}
?}// 1、定義事件監(jiān)聽(tīng)接口
?public?interface?MethodMonitorEventListener?extends?EventListener?{
?????// 處理方法執(zhí)行之前發(fā)布的事件
?????public?void?onMethodBegin(MethodMonitorEvent event);
?????// 處理方法結(jié)束時(shí)發(fā)布的事件
?????public?void?onMethodEnd(MethodMonitorEvent event);
?}
?// 2、事件監(jiān)聽(tīng)接口的實(shí)現(xiàn)：如何處理
?public?class?AbstractMethodMonitorEventListener?implements?MethodMonitorEventListener?{
??????@Override
?????public?void?onMethodBegin(MethodMonitorEvent event) {
?????????// 記錄方法開(kāi)始執(zhí)行時(shí)的時(shí)間
?????????event.timestamp = System.currentTimeMillis();
?????}
??????@Override
?????public?void?onMethodEnd(MethodMonitorEvent event) {
?????????// 計(jì)算方法耗時(shí)
?????????long?duration = System.currentTimeMillis() - event.timest
?????????System.out.println("耗時(shí)："?+ duration);
?????}
?}public?class?MethodMonitorEventPublisher?{
??????private?Listlisteners = new?ArrayList();
??????public?void?methodMonitor() {
?????????MethodMonitorEvent eventObject = new?MethodMonitorEvent(this);
?????????publishEvent("begin",eventObject);
?????????// 模擬方法執(zhí)行：休眠5秒鐘
?????????TimeUnit.SECONDS.sleep(5);
?????????publishEvent("end",eventObject);
??????}
??????private?void?publishEvent(String status,MethodMonitorEvent event) {
?????????// 避免在事件處理期間，監(jiān)聽(tīng)器被移除，這里為了安全做一個(gè)復(fù)制操作
?????????ListcopyListeners = ? new?ArrayList(listeners);
?????????for?(MethodMonitorEventListener listener : copyListeners) {
?????????????if?("begin".equals(status)) {
?????????????????listener.onMethodBegin(event);
?????????????} else?{
?????????????????listener.onMethodEnd(event);
?????????????}
?????????}
?????}
?????????public?static?void?main(String[] args) {
?????????MethodMonitorEventPublisher publisher = new?MethodMonitorEventPublisher();
?????????publisher.addEventListener(new?AbstractMethodMonitorEventListener());
?????????publisher.methodMonitor();
?????}
?????// 省略實(shí)現(xiàn)
?????public?void?addEventListener(MethodMonitorEventListener listener) {}
?????public?void?removeEventListener(MethodMonitorEventListener listener) {}
?????public?void?removeAllListeners() {} 2. 事件監(jiān)聽(tīng)器的管理。publisher類(lèi)中提供了事件監(jiān)聽(tīng)器的注冊(cè)與移除方法，這樣客戶(hù)端可以根據(jù)實(shí)際情況決定是否需要注冊(cè)新的監(jiān)聽(tīng)器或者移除某個(gè)監(jiān)聽(tīng)器。
@SpringBootApplication
?public?class?MoonApplication?{
??????public?static?void?main(String[] args)?{
?????????SpringApplication.run(MoonApplication.class, args);
?????}
?}@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 {
?????// ......
?}@Target(ElementType.TYPE)
?@Retention(RetentionPolicy.RUNTIME)
?@Documented
?@Inherited
?@AutoConfigurationPackage
?@Import(EnableAutoConfigurationImportSelector.class)
?public @interface?EnableAutoConfiguration {
?????// ......
?}public?String[] selectImports(AnnotationMetadata annotationMetadata) {
?????// 省略了大部分代碼，保留一句核心代碼
?????// 注意：SpringBoot最近版本中，這句代碼被封裝在一個(gè)單獨(dú)的方法中
?????// SpringFactoriesLoader相關(guān)知識(shí)請(qǐng)參考前文
?????List<String> factories = new?ArrayList<String>(new?LinkedHashSet<String>(
???????????SpringFactoriesLoader.loadFactoryNames(EnableAutoConfiguration.class, this.beanClassLoader)));
?}// 來(lái)自 org.springframework.boot.autoconfigure下的META-INF/spring.factories
?// 配置的key = EnableAutoConfiguration，與代碼中一致
?org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
?org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
?org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
?org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration\
?.....@Configuration
?@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
?@EnableConfigurationProperties(DataSourceProperties.class)
?@Import({ Registrar.class, DataSourcePoolMetadataProvidersConfiguration.class })
?public class DataSourceAutoConfiguration {
?}// 提供對(duì)datasource配置信息的支持，所有的配置前綴為：spring.datasource
?@ConfigurationProperties(prefix = "spring.datasource")
?public?class?DataSourceProperties {
?????private?ClassLoader classLoader;
?????private?Environment environment;
?????private?String?name = "testdb";
?????......
?}@Configuration
?public class DataSourcePoolMetadataProvidersConfiguration {
??????@Configuration
?????@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
?????static class TomcatDataSourcePoolMetadataProviderConfiguration {
?????????@Bean
?????????public DataSourcePoolMetadataProvider tomcatPoolDataSourceMetadataProvider() {
?????????????.....
?????????}
?????}
???......
?}
private?void?initialize(Object[] sources) {
??????if?(sources != null?&& sources.length > 0) {
??????????this.sources.addAll(Arrays.asList(sources));
??????}
??????// 判斷是否是Web項(xiàng)目
??????this.webEnvironment = deduceWebEnvironment();
??????setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
??????setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
??????// 找到入口類(lèi)
??????this.mainApplicationClass = deduceMainApplicationClass();
?}org.springframework.context.ApplicationListener=\ cn.moondev.listeners.xxxxListener\public?ConfigurableApplicationContext run(String... args) {
?????????StopWatch stopWatch = new?StopWatch();
?????????stopWatch.start();
?????????ConfigurableApplicationContext context = null;
?????????FailureAnalyzers analyzers = null;
?????????configureHeadlessProperty();
?????????// ①
?????????SpringApplicationRunListeners listeners = getRunListeners(args);
?????????listeners.starting();
?????????try?{
?????????????// ②
ApplicationArguments applicationArguments = new?DefaultApplicationArguments(args);
?????????????ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
?????????????// ③
?????????????Banner printedBanner = printBanner(environment);
?????????????// ④
?????????????context = createApplicationContext();
?????????????// ⑤
?????????????analyzers = new?FailureAnalyzers(context);
?????????????// ⑥
?????????????prepareContext(context, environment, listeners, applicationArguments,printedBanner);
?????????????// ⑦
??????????????refreshContext(context);
?????????????// ⑧
?????????????afterRefresh(context, applicationArguments);
?????????????// ⑨
?????????????listeners.finished(context, null);
?????????????stopWatch.stop();
?????????????return?context;
????????}
?????????catch?(Throwable ex) {
?????????????handleRunFailure(context, listeners, analyzers, ex);
?????????????throw?new?IllegalStateException(ex);
?????????}
?????}public?interface?SpringApplicationRunListener?{
??????// 運(yùn)行run方法時(shí)立即調(diào)用此方法，可以用戶(hù)非常早期的初始化工作
?????void?starting();
??????????// Environment準(zhǔn)備好后，并且ApplicationContext創(chuàng)建之前調(diào)用
?????void?environmentPrepared(ConfigurableEnvironment environment);
??????// ApplicationContext創(chuàng)建好后立即調(diào)用
?????void?contextPrepared(ConfigurableApplicationContext context);
??????// ApplicationContext加載完成，在refresh之前調(diào)用
?????void?contextLoaded(ConfigurableApplicationContext context);
??????// 當(dāng)run方法結(jié)束之前調(diào)用
?????void?finished(ConfigurableApplicationContext
?context, Throwable exception);
??}public?void?starting()?{
?????// 發(fā)布一個(gè)ApplicationStartedEvent
?????this.initialMulticaster.multicastEvent(new?ApplicationStartedEvent(this.application, this.args));
?}listeners.environmentPrepared(environment);. ____??????????_????????????__?_?_
??/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
?( ( )\___ | '_?| '_|?| '_ \/ _` |?\ \ \ \
??\\/ ___)| |_)| |?| |?| || (_|?| ) ) ) )
???' |____| .__|_| |_|_|?|_\__, |?/ / /?/
??=========|_|==============|___/=/_/_/_/
?:: Spring Boot :: (v1.5.6.RELEASE)// 摘自refresh()方法中一句代碼
?invokeBeanFactoryPostProcessors(beanFactory);protected?void?invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory)?{
?????PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
?????......
?}ConfigurationWarningsApplicationContextInitializer$ConfigurationWarningsPostProcessor
?SharedMetadataReaderFactoryContextInitializer$CachingMetadataReaderFactoryPostProcessor
?ConfigFileApplicationListener$PropertySourceOrderingPostProcessorpublic?void?initialize(ConfigurableApplicationContext context)?{
?????context.addBeanFactoryPostProcessor(new?ConfigurationWarningsPostProcessor(getChecks()));
?}作者：CHEN川
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