SpringBoot启动流程SpringApplication准备阶段源码分析

package org.springframework.boot; public ConfigurableApplicationContext run(String... args) { //1.计时器 StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; Collection exceptionReporters = new ArrayList<>(); //2.headless配置 configureHeadlessProperty(); //3、获取监听 SpringApplicationRunListeners listeners = getRunListeners(args); listeners.starting(); try { //应用程序启动的参数 ApplicationArguments applicationArguments = new DefaultApplicationArguments(args); //4、准备环境 ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments); //环境创建成功后，配置bean信息，决定是否跳过 BeanInfo 类的扫描，如果设置为 true,则跳过 configureIgnoreBeanInfo(environment); //打印banner信息 Banner printedBanner = printBanner(environment); context = createApplicationContext(); exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[] { ConfigurableApplicationContext.class }, context); prepareContext(context, environment, listeners, applicationArguments, printedBanner); refreshContext(context); afterRefresh(context, applicationArguments); //停止计时 stopWatch.stop(); //控制是否打印日志的,这里为true，即打印日志 if (this.logStartupInfo) { new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch); } listeners.started(context); callRunners(context, applicationArguments); } catch (Throwable ex) { handleRunFailure(context, ex, exceptionReporters, listeners); throw new IllegalStateException(ex); } try { listeners.running(context); } catch (Throwable ex) { handleRunFailure(context, ex, exceptionReporters, null); throw new IllegalStateException(ex); } return context; } 

StopWatch stopWatch = new StopWatch(); //开始计时 stopWatch.start(); //停止计时 stopWatch.stop(); 

//将当前类传入StartupInfoLogger创建了一个对象 //然后调用logStarted打印日志 new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch); //创建一个Log类 protected Log getApplicationLog() { if (this.mainApplicationClass == null) { return logger; } return LogFactory.getLog(this.mainApplicationClass); } //调用log类的log.info()方法来打印日志 public void logStarted(Log log, StopWatch stopWatch) { if (log.isInfoEnabled()) { log.info(getStartedMessage(stopWatch)); } } //打印详细的日志 private StringBuilder getStartedMessage(StopWatch stopWatch) { StringBuilder message = new StringBuilder(); message.append("Started "); message.append(getApplicationName()); message.append(" in "); message.append(stopWatch.getTotalTimeSeconds()); try { double uptime = ManagementFactory.getRuntimeMXBean().getUptime() / 1000.0; message.append(" seconds (JVM running for " + uptime + ")"); } catch (Throwable ex) { // No JVM time available } return message; } 

private static final String SYSTEM_PROPERTY_JAVA_AWT_HEADLESS = "java.awt.headless"; private void configureHeadlessProperty() { System.setProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, System.getProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, Boolean.toString(this.headless))); } 

//获取所有监听 SpringApplicationRunListeners listeners = getRunListeners(args); //启动监听 listeners.starting(); 

private SpringApplicationRunListeners getRunListeners(String[] args) { Class[] types = new Class[] { SpringApplication.class, String[].class }; return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args)); } private  Collection getSpringFactoriesInstances(Class type, Class[] parameterTypes, Object... args) { //3.1获取类加载器 ClassLoader classLoader = getClassLoader(); // Use names and ensure unique to protect against duplicates //3.2 根据类型获取spring.factories中符合的类名 Set names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader)); //3.3 创建类实例 List instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names); //对实例进行排序 AnnotationAwareOrderComparator.sort(instances); return instances; } 

/** * A collection of {@link SpringApplicationRunListener}. * * @author Phillip Webb */ class SpringApplicationRunListeners { private final Log log; private final List listeners; SpringApplicationRunListeners(Log log, Collection listeners) { this.log = log; this.listeners = new ArrayList<>(listeners); } 

/** *//可以理解为Spring Boot应用的运行时监听器 * Listener for the {@link SpringApplication} {@code run} method. *//SpringApplicationRunListener的构造器参数必须依次为SpringApplication和String[]类型 * {@link SpringApplicationRunListener}s are loaded via the {@link SpringFactoriesLoader} * and should declare a public constructor that accepts a {@link SpringApplication} * instance and a {@code String[]} of arguments. *//每次运行的时候将会创建一个 SpringApplicationRunListener A new * {@link SpringApplicationRunListener} instance will be created for each run. * */ public interface SpringApplicationRunListener { /** * Called immediately when the run method has first started. Can be used for very * early initialization. */ //Spring应用刚启动 void starting(); /** * Called once the environment has been prepared, but before the * {@link ApplicationContext} has been created. * @param environment the environment */ //ConfigurableEnvironment准备妥当，允许将其调整 void environmentPrepared(ConfigurableEnvironment environment); /** * Called once the {@link ApplicationContext} has been created and prepared, but * before sources have been loaded. * @param context the application context */ //ConfigurableApplicationContext准备妥当，允许将其调整 void contextPrepared(ConfigurableApplicationContext context); /** * Called once the application context has been loaded but before it has been * refreshed. * @param context the application context */ //ConfigurableApplicationContext已装载，但是任未启动 void contextLoaded(ConfigurableApplicationContext context); /** * The context has been refreshed and the application has started but * {@link CommandLineRunner CommandLineRunners} and {@link ApplicationRunner * ApplicationRunners} have not been called. * @param context the application context. * @since 2.0.0 */ //ConfigurableApplicationContext已启动，此时Spring Bean已初始化完成 void started(ConfigurableApplicationContext context); /** * Called immediately before the run method finishes, when the application context has * been refreshed and all {@link CommandLineRunner CommandLineRunners} and * {@link ApplicationRunner ApplicationRunners} have been called. * @param context the application context. * @since 2.0.0 */ //Spring应用正在运行 void running(ConfigurableApplicationContext context); /** * Called when a failure occurs when running the application. * @param context the application context or {@code null} if a failure occurred before * the context was created * @param exception the failure * @since 2.0.0 */ //Spring应用运行失败 void failed(ConfigurableApplicationContext context, Throwable exception); } 

public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered { private final SpringApplication application; private final String[] args; private final SimpleApplicationEventMulticaster initialMulticaster; public EventPublishingRunListener(SpringApplication application, String[] args) { this.application = application; this.args = args; this.initialMulticaster = new SimpleApplicationEventMulticaster(); for (ApplicationListener listener : application.getListeners()) { this.initialMulticaster.addApplicationListener(listener); } } 

ClassLoader classLoader = getClassLoader(); public ClassLoader getClassLoader() { if (this.resourceLoader != null) { return this.resourceLoader.getClassLoader(); } return ClassUtils.getDefaultClassLoader(); } 

SpringFactoriesLoader.loadFactoryNames(type, classLoader) public static List loadFactoryNames(Class factoryClass, @Nullable ClassLoader classLoader) { //获取类型名称：org.springframework.context.ApplicationContextInitializer String factoryClassName = factoryClass.getName(); return (List)loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList()); } 

private static Map> loadSpringFactories(@Nullable ClassLoader classLoader) { //从缓存里面获取 MultiValueMap result = (MultiValueMap)cache.get(classLoader); if (result != null) { return result; } else { try { //执行classLoader.getResources("META-INF/spring.factories")，表示通过加载器获取META-INF/spring.factories下的资源 Enumeration urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories"); LinkedMultiValueMap result = new LinkedMultiValueMap(); while(urls.hasMoreElements()) { //文件地址 URL url = (URL)urls.nextElement(); //从指定位置加载UrlResource UrlResource resource = new UrlResource(url); //加载里面的属性，属性见下图 Properties properties = PropertiesLoaderUtils.loadProperties(resource); Iterator var6 = properties.entrySet().iterator(); while(var6.hasNext()) { Entry entry = (Entry)var6.next(); //获取key值 String factoryClassName = ((String)entry.getKey()).trim(); //获取value值 String[] var9 = StringUtils.commaDelimitedListToStringArray((String)entry.getValue()); int var10 = var9.length; //这里是将查询出来的key作为result的key,value转换成字符数组存放到result的value中 for(int var11 = 0; var11 

default V getOrDefault(Object key, V defaultValue) { V v; return (((v = get(key)) != null) || containsKey(key)) ? v : defaultValue; } 

private  List createSpringFactoriesInstances()(Class type, Class[] parameterTypes, ClassLoader classLoader, Object[] args, Set names) { List instances = new ArrayList<>(names.size()); for (String name : names) { try { //根据类加载器获取指定类 Class instanceClass = ClassUtils.forName(name, classLoader); Assert.isAssignable(type, instanceClass); //根据参数获取构造器 Constructor constructor = instanceClass.getDeclaredConstructor(parameterTypes); //根据传入的构造器对象以及构造器所需的参数创建一个实例 T instance = (T) BeanUtils.instantiateClass(constructor, args); //添加实例到集合中 instances.add(instance); } catch (Throwable ex) { throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex); } } return instances; } 

prepareEnvironment(listeners, applicationArguments) 

private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) { // Create and configure the environment //4.1 创建一个环境 ConfigurableEnvironment environment = getOrCreateEnvironment(); //4.2 配置环境 configureEnvironment(environment, applicationArguments.getSourceArgs()); //4.3 ConfigurationPropertySourcesPropertySource对象存入到第一位 ConfigurationPropertySources.attach(environment); //listeners环境准备(就是广播ApplicationEnvironmentPreparedEvent事件) listeners.environmentPrepared(environment); // 将环境绑定到SpringApplication bindToSpringApplication(environment); // 如果是非web环境，将环境转换成StandardEnvironment if (!this.isCustomEnvironment) { environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment, deduceEnvironmentClass()); } // 配置PropertySources对它自己的递归依赖 ConfigurationPropertySources.attach(environment); return environment; } 

private ConfigurableEnvironment getOrCreateEnvironment() { //有的话，直接返回 if (this.environment != null) { return this.environment; } //这里我们在上面见到过，通过WebApplicationType.deduceFromClasspath()方法获取的 switch (this.webApplicationType) { case SERVLET: return new StandardServletEnvironment(); case REACTIVE: return new StandardReactiveWebEnvironment(); default: return new StandardEnvironment(); } } 

protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) { if (this.addConversionService) { ConversionService conversionService = ApplicationConversionService.getSharedInstance(); environment.setConversionService((ConfigurableConversionService) conversionService); } configurePropertySources(environment, args); configureProfiles(environment, args); } 

protected void configurePropertySources(ConfigurableEnvironment environment, String[] args) { //获取所有的属性源，就是获取4.1的ConfigurableEnvironment上获取到的属性 MutablePropertySources sources = environment.getPropertySources(); if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) { sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties)); } //是否添加命令启动参数，addCommandLineProperties为true，表示需要添加，但是前提是你得配置了参数 if (this.addCommandLineProperties && args.length > 0) { String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME; if (sources.contains(name)) { PropertySource source = sources.get(name); CompositePropertySource composite = new CompositePropertySource(name); composite.addPropertySource( new SimpleCommandLinePropertySource("springApplicationCommandLineArgs", args)); composite.addPropertySource(source); sources.replace(name, composite); } else { sources.addFirst(new SimpleCommandLinePropertySource(args)); } } } 

protected void configureProfiles(ConfigurableEnvironment environment, String[] args) { //获取激活的环境 environment.getActiveProfiles(); // ensure they are initialized // But these ones should go first (last wins in a property key clash) Set profiles = new LinkedHashSet<>(this.additionalProfiles); profiles.addAll(Arrays.asList(environment.getActiveProfiles())); //设置当前的环境 environment.setActiveProfiles(StringUtils.toStringArray(profiles)); } 

public static void attach(Environment environment) { Assert.isInstanceOf(ConfigurableEnvironment.class, environment); //获取所有的属性源，就是获取4.1的ConfigurableEnvironment上获取到的属性 MutablePropertySources sources = ((ConfigurableEnvironment) environment).getPropertySources(); //判断是否有 属性 configurationProperties PropertySource attached = sources.get(ATTACHED_PROPERTY_SOURCE_NAME); if (attached != null && attached.getSource() != sources) { sources.remove(ATTACHED_PROPERTY_SOURCE_NAME); attached = null; } if (attached == null) { // 将sources封装成ConfigurationPropertySourcesPropertySource对象，并把这个对象放到sources的第一位置 sources.addFirst(new ConfigurationPropertySourcesPropertySource(ATTACHED_PROPERTY_SOURCE_NAME, new SpringConfigurationPropertySources(sources))); } }