摘要
本文讲解了SpringBoot的启动过程中涉及到的一些点
springboot 启动过程源码解析
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原文链接：springboot 启动过程源码解析
详细的启动步骤如下：
1、创建并启动计时监控类
2、初始化应用上下文和异常报告集合
3、设置系统属性java.awt.headless的值：
4、创建所有spring运行监听器并发布应用启动事件
5、初始化默认应用参数类
6、根据运行监听器和应用参数来准备spring环境信息
7、打印banner
8、创建应用的上下文:
9、准备异常报告器
10、准备应用上下文
11、刷新应用上下文
12、应用上下文刷新后置处理
13、停止计时监控类
14、输出日志记录执行主类名、时间信息
15、发布应用上下文启动完成事件
16、执行所有Runner执行器
17、发布应用上下文就绪事件
18、返回应用上下文
启动过程导图
大维度下启动过程
1、springboot的入口程序
@SpringBootApplication
public class StartupApplication {
public static void main(String[] args) {
SpringApplication.run(StartupApplication.class, args);
}
}2、构造SpringApplication
当程序开始执行之后，会调用SpringApplication的构造方法，进行某些初始参数的设置
//创建一个新的实例，这个应用程序的上下文将要从指定的来源加载Bean
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
//资源初始化资源加载器，默认为null
this.resourceLoader = resourceLoader;
//断言主要加载资源类不能为 null，否则报错
Assert.notNull(primarySources, "PrimarySources must not be null");
//初始化主要加载资源类集合并去重
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
//推断当前 WEB 应用类型，一共有三种：NONE,SERVLET,REACTIVE
this.webApplicationType = WebApplicationType.deduceFromClasspath();
//设置应用上线文初始化器,从"META-INF/spring.factories"读取ApplicationContextInitializer类的实例名称集合并去重，并进行set去重。（一共7个）
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
//设置监听器,从"META-INF/spring.factories"读取ApplicationListener类的实例名称集合并去重，并进行set去重。（一共11个）
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
//推断主入口应用类，通过当前调用栈，获取Main方法所在类，并赋值给mainApplicationClass
this.mainApplicationClass = deduceMainApplicationClass();
}在上述构造方法中，有一个判断应用类型的方法，用来判断当前应用程序的类型：
static WebApplicationType deduceFromClasspath() {
if (ClassUtils.isPresent(WEBFLUX_INDICATOR_CLASS, null) && !ClassUtils.isPresent(WEBMVC_INDICATOR_CLASS, null)
&& !ClassUtils.isPresent(JERSEY_INDICATOR_CLASS, null)) {
return WebApplicationType.REACTIVE;
}
for (String className : SERVLET_INDICATOR_CLASSES) {
if (!ClassUtils.isPresent(className, null)) {
return WebApplicationType.NONE;
}
}
return WebApplicationType.SERVLET;
}
//WebApplicationType的类型
public enum WebApplicationType {
/**
* The application should not run as a web application and should not start an
* embedded web server.
* 非web项目
*/
NONE,
/**
* The application should run as a servlet-based web application and should start an
* embedded servlet web server.
* servlet web 项目
*/
SERVLET,
/**
* The application should run as a reactive web application and should start an
* embedded reactive web server.
* 响应式 web 项目
*/
REACTIVE;3、执行Run方法
springboot启动的运行方法，可以看到主要是各种运行环境的准备工作
public ConfigurableApplicationContext run(String... args) {
//1、创建并启动计时监控类
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//2、初始化应用上下文和异常报告集合
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
//3、设置系统属性“java.awt.headless”的值，默认为true，用于运行headless服务器，进行简单的图像处理，多用于在缺少显示屏、键盘或者鼠标时的系统配置，很多监控工具如jconsole 需要将该值设置为true
configureHeadlessProperty();
//4、创建所有spring运行监听器并发布应用启动事件，简单说的话就是获取SpringApplicationRunListener类型的实例（EventPublishingRunListener对象），并封装进SpringApplicationRunListeners对象，然后返回这个SpringApplicationRunListeners对象。说的再简单点，getRunListeners就是准备好了运行时监听器EventPublishingRunListener。
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
//5、初始化默认应用参数类
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
//6、根据运行监听器和应用参数来准备spring环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
//将要忽略的bean的参数打开
configureIgnoreBeanInfo(environment);
//7、创建banner打印类
Banner printedBanner = printBanner(environment);
//8、创建应用上下文，可以理解为创建一个容器
context = createApplicationContext();
//9、准备异常报告器，用来支持报告关于启动的错误
exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
//10、准备应用上下文，该步骤包含一个非常关键的操作，将启动类注入容器，为后续开启自动化提供基础
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
//11、刷新应用上下文
refreshContext(context);
//12、应用上下文刷新后置处理，做一些扩展功能
afterRefresh(context, applicationArguments);
//13、停止计时监控类
stopWatch.stop();
//14、输出日志记录执行主类名、时间信息
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}
//15、发布应用上下文启动监听事件
listeners.started(context);
//16、执行所有的Runner运行器
callRunners(context, applicationArguments);
}catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, listeners);
throw new IllegalStateException(ex);
}
try {
//17、发布应用上下文就绪事件
listeners.running(context);
}catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, null);
throw new IllegalStateException(ex);
}
//18、返回应用上下文
return context;
}详细的启动过程
下面详细介绍各个启动的环节：
1、创建并启动计时监控类
创建并启动计时监控类，可以看到记录当前任务的名称，默认是空字符串，然后记录当前springboot应用启动的开始时间。
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//详细源代码
public void start() throws IllegalStateException {
start("");
}
public void start(String taskName) throws IllegalStateException {
if (this.currentTaskName != null) {
throw new IllegalStateException("Can't start StopWatch: it's already running");
}
this.currentTaskName = taskName;
this.startTimeNanos = System.nanoTime();
}2、初始化应用上下文和异常报告集合
ConfigurableApplicationContext context = null; Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
3、设置系统属性java.awt.headless的值
/*
java.awt.headless模式是在缺少显示屏、键盘或者鼠标的系统配置
当配置了如下属性之后，应用程序可以执行如下操作：
1、创建轻量级组件
2、收集关于可用的字体、字体指标和字体设置的信息
3、设置颜色来渲染准备图片
4、创造和获取图像，为渲染准备图片
5、使用java.awt.PrintJob,java.awt.print.*和javax.print.*类里的方法进行打印
*/
private void configureHeadlessProperty() {
System.setProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS,
System.getProperty(SYSTEM_PROPERTY_JAVA_AWT_HEADLESS, Boolean.toString(this.headless)));
}4、创建所有spring运行监听器并发布应用启动事件
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
//创建spring监听器
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
return new SpringApplicationRunListeners(logger,
getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
}
SpringApplicationRunListeners(Log log, Collection<? extends SpringApplicationRunListener> listeners) {
this.log = log;
this.listeners = new ArrayList<>(listeners);
}
//创建监听器的实例，createSpringFactoriesInstances方法中使用反射创建实例
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = getClassLoader();
// Use names and ensure unique to protect against duplicates
Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
回到SpringApplication中的run方法
-------------
listeners.starting();//监听器启动
//循环遍历获取监听器
void starting() {
for (SpringApplicationRunListener listener : this.listeners) {
listener.starting();//事件监听机制：观察者模式、回调、委托
}
}
//此处的监听器可以看出是事件发布监听器，主要用来发布启动事件
@Override
public void starting() {
//这里是创建application事件‘applicationStartingEvent’
this.initialMulticaster.multicastEvent(new ApplicationStartingEvent(this.application, this.args));
}
//applicationStartingEvent是springboot框架最早执行的监听器，
// 在该监听器执行started方法时，会继续发布事件，主要是基于spring的事件机制
@Override
public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
//获取线程池，如果为空则同步处理。这里线程池为空，还未初始化
Executor executor = getTaskExecutor();
for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {
if (executor != null) {
//异步发送事件
executor.execute(() -> invokeListener(listener, event));
}
else {
//同步发送事件
invokeListener(listener, event);
}
}
}5、初始化默认应用参数类
处理命令行中的参数，比如说Java -jar -Xms等等
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
public DefaultApplicationArguments(String... args) {
Assert.notNull(args, "Args must not be null");
this.source = new Source(args);
this.args = args;
}
Source(String[] args) {
super(args);
}
//从main方法中解析命令行参数
public CommandLineArgs parse(String... args) {
CommandLineArgs commandLineArgs = new CommandLineArgs();
for (String arg : args) {
if (arg.startsWith("--")) {
String optionText = arg.substring(2);
String optionName;
String optionValue = null;
int indexOfEqualsSign = optionText.indexOf('=');
if (indexOfEqualsSign > -1) {
optionName = optionText.substring(0, indexOfEqualsSign);
optionValue = optionText.substring(indexOfEqualsSign + 1);
}
else {
optionName = optionText;
}
if (optionName.isEmpty()) {
throw new IllegalArgumentException("Invalid argument syntax: " + arg);
}
commandLineArgs.addOptionArg(optionName, optionValue);
}
else {
commandLineArgs.addNonOptionArg(arg);
}
}
return commandLineArgs;
}6、根据运行监听器和应用参数来准备spring环境信息
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
//详细环境的准备
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// 获取或者创建应用环境
ConfigurableEnvironment environment = getOrCreateEnvironment();
// 配置应用环境，配置propertySource和activeProfiles
configureEnvironment(environment, applicationArguments.getSourceArgs());
//listeners环境准备，广播ApplicationEnvironmentPreparedEvent
ConfigurationPropertySources.attach(environment);
//监听配置文件，后面又到了Spring中的事件发布模式
listeners.environmentPrepared(environment);
//将环境绑定给当前应用程序
bindToSpringApplication(environment);
//对当前的环境类型进行判断，如果不一致进行转换
if (!this.isCustomEnvironment) {
environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
//配置propertySource对它自己的递归依赖
//转换之后，重新一次
ConfigurationPropertySources.attach(environment);
return environment;
}
// 获取或者创建应用环境，根据应用程序的类型可以分为servlet环境、标准环境(特殊的非web环境)和响应式环境
private ConfigurableEnvironment getOrCreateEnvironment() {
//存在则直接返回
if (this.environment != null) {
return this.environment;
}
//根据webApplicationType创建对应的Environment
switch (this.webApplicationType) {
case SERVLET:
return new StandardServletEnvironment();
case REACTIVE:
return new StandardReactiveWebEnvironment();
default:
return new StandardEnvironment();
}
}
//配置应用环境
protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {
if (this.addConversionService) {
ConversionService conversionService = ApplicationConversionService.getSharedInstance();
environment.setConversionService((ConfigurableConversionService) conversionService);
}
//配置property sources
configurePropertySources(environment, args);
//配置profiles
configureProfiles(environment, args);
}
//监听配置文件
listeners.environmentPrepared(environment);7、打印banner
Banner printedBanner = printBanner(environment);
//打印类的详细操作过程
private Banner printBanner(ConfigurableEnvironment environment) {
if (this.bannerMode == Banner.Mode.OFF) {
return null;
}
ResourceLoader resourceLoader = (this.resourceLoader != null) ? this.resourceLoader
: new DefaultResourceLoader(getClassLoader());
SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter(resourceLoader, this.banner);
if (this.bannerMode == Mode.LOG) {
return bannerPrinter.print(environment, this.mainApplicationClass, logger);
}
return bannerPrinter.print(environment, this.mainApplicationClass, System.out);
}
Banner print(Environment environment, Class<?> sourceClass, PrintStream out) {
Banner banner = getBanner(environment);
banner.printBanner(environment, sourceClass, out);
return new PrintedBanner(banner, sourceClass);
}
//需要打印的字符串
private static final String[] BANNER = { "", " . ____ _ __ _ _",
" /\\\\ / ___'_ __ _ _(_)_ __ __ _ \\ \\ \\ \\", "( ( )\\___ | '_ | '_| | '_ \\/ _` | \\ \\ \\ \\",
" \\\\/ ___)| |_)| | | | | || (_| | ) ) ) )", " ' |____| .__|_| |_|_| |_\\__, | / / / /",
" =========|_|==============|___/=/_/_/_/" };
//打印Banner
public void printBanner(Environment environment, Class<?> sourceClass, PrintStream printStream) {
for (String line : BANNER) {
printStream.println(line);
}
String version = SpringBootVersion.getVersion();
version = (version != null) ? " (v" + version + ")" : "";
StringBuilder padding = new StringBuilder();
while (padding.length() < STRAP_LINE_SIZE - (version.length() + SPRING_BOOT.length())) {
padding.append(" ");
}
printStream.println(AnsiOutput.toString(AnsiColor.GREEN, SPRING_BOOT, AnsiColor.DEFAULT, padding.toString(),
AnsiStyle.FAINT, version));
printStream.println();
}8、创建应用的上下文:
根据不同的应用类型初始化不同的上下文应用类
context = createApplicationContext();
//用于创建不同上下文类的策略方法
protected ConfigurableApplicationContext createApplicationContext() {
Class<?> contextClass = this.applicationContextClass;
if (contextClass == null) {
try {
switch (this.webApplicationType) {
case SERVLET:
contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
break;
case REACTIVE:
contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
break;
default:
contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
}
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Unable create a default ApplicationContext, please specify an ApplicationContextClass", ex);
}
}
return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
}
//根据className,进行反射获取实例
public static <T> T instantiateClass(Class<T> clazz) throws BeanInstantiationException {
Assert.notNull(clazz, "Class must not be null");
if (clazz.isInterface()) {
throw new BeanInstantiationException(clazz, "Specified class is an interface");
}
try {
return instantiateClass(clazz.getDeclaredConstructor());
}
catch (NoSuchMethodException ex) {
Constructor<T> ctor = findPrimaryConstructor(clazz);
if (ctor != null) {
return instantiateClass(ctor);
}
throw new BeanInstantiationException(clazz, "No default constructor found", ex);
}
catch (LinkageError err) {
throw new BeanInstantiationException(clazz, "Unresolvable class definition", err);
}
}
public T newInstance(Object ... initargs)
throws InstantiationException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, null, modifiers);
}
}
if ((clazz.getModifiers() & Modifier.ENUM) != 0)
throw new IllegalArgumentException("Cannot reflectively create enum objects");
ConstructorAccessor ca = constructorAccessor; // read volatile
if (ca == null) {
ca = acquireConstructorAccessor();
}
//反射获取对象
@SuppressWarnings("unchecked")
T inst = (T) ca.newInstance(initargs);
return inst;
}9、准备异常报告器
exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = getClassLoader();
// Use names and ensure unique to protect against duplicates
Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}10、准备应用上下文
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
//应用上下文的environment
context.setEnvironment(environment);
//应用上下文后处理
postProcessApplicationContext(context);
//为上下文应用所有初始化器，
//执行容器中的applicationContextInitializer(spring.factories的实例)，
//将所有的初始化对象放置到context对象中
applyInitializers(context);
//触发所有SpringApplicationRunListener监听器的ContextPrepared事件方法。添加所有的事件监听器
listeners.contextPrepared(context);
//记录启动日志
if (this.logStartupInfo) {
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// 注册启动参数bean，将容器指定的参数封装成bean，注入容器
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
//设置banner
if (printedBanner != null) {
beanFactory.registerSingleton("springBootBanner", printedBanner);
}
if (beanFactory instanceof DefaultListableBeanFactory) {
((DefaultListableBeanFactory) beanFactory)
.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.lazyInitialization) {
context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}
// 加载所有资源，指的是启动器指定的参数
Set<Object> sources = getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
//将bean加载到上下文中,注册启动程序SpringApplication
load(context, sources.toArray(new Object[0]));
//触发所有springapplicationRunListener监听器的contextLoaded事件方法，
listeners.contextLoaded(context);
}
-------------------
//这里没有做任何的处理过程，因为beanNameGenerator和resourceLoader默认为空，可以方便后续做扩展处理
protected void postProcessApplicationContext(ConfigurableApplicationContext context) {
if (this.beanNameGenerator != null) {
context.getBeanFactory().registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR,
this.beanNameGenerator);
}
if (this.resourceLoader != null) {
if (context instanceof GenericApplicationContext) {
((GenericApplicationContext) context).setResourceLoader(this.resourceLoader);
}
if (context instanceof DefaultResourceLoader) {
((DefaultResourceLoader) context).setClassLoader(this.resourceLoader.getClassLoader());
}
}
if (this.addConversionService) {
context.getBeanFactory().setConversionService(ApplicationConversionService.getSharedInstance());
}
}
---------------------
//将启动器类加载到spring容器中，为后续的自动化配置奠定基础，之前看到的很多注解也与此相关
protected void load(ApplicationContext context, Object[] sources) {
if (logger.isDebugEnabled()) {
logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources));
}
BeanDefinitionLoader loader = createBeanDefinitionLoader(getBeanDefinitionRegistry(context), sources);
if (this.beanNameGenerator != null) {
loader.setBeanNameGenerator(this.beanNameGenerator);
}
if (this.resourceLoader != null) {
loader.setResourceLoader(this.resourceLoader);
}
if (this.environment != null) {
loader.setEnvironment(this.environment);
}
loader.load();
}
---------------------
//判断类型，我们这里走Class类型
private int load(Object source) {
Assert.notNull(source, "Source must not be null");
if (source instanceof Class<?>) {
return load((Class<?>) source);
}
if (source instanceof Resource) {
return load((Resource) source);
}
if (source instanceof Package) {
return load((Package) source);
}
if (source instanceof CharSequence) {
return load((CharSequence) source);
}
throw new IllegalArgumentException("Invalid source type " + source.getClass());
}
//springboot会优先选择groovy加载方式，找不到在选择java方式
private int load(Class<?> source) {
if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
// Any GroovyLoaders added in beans{} DSL can contribute beans here
GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
load(loader);
}
if (isEligible(source)) {
this.annotatedReader.register(source); //注册Bean
return 1;
}
return 0;
}
//传入启动类
public void registerBean(Class<?> beanClass) {
doRegisterBean(beanClass, null, null, null, null);
}
//传入启动类，进行注册
private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name,
@Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier,
@Nullable BeanDefinitionCustomizer[] customizers) {
AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass);
if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
return;
}
abd.setInstanceSupplier(supplier);
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
abd.setScope(scopeMetadata.getScopeName());
String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
if (qualifiers != null) {
for (Class<? extends Annotation> qualifier : qualifiers) {
if (Primary.class == qualifier) {
abd.setPrimary(true);
}
else if (Lazy.class == qualifier) {
abd.setLazyInit(true);
}
else {
abd.addQualifier(new AutowireCandidateQualifier(qualifier));
}
}
}
if (customizers != null) {
for (BeanDefinitionCustomizer customizer : customizers) {
customizer.customize(abd);
}
}
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
//注册
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
}11、刷新应用上下文
refreshContext(context);
private void refreshContext(ConfigurableApplicationContext context) {
refresh(context);
if (this.registerShutdownHook) {
try {
context.registerShutdownHook();
}
catch (AccessControlException ex) {
// Not allowed in some environments.
}
}
}
//AbstractApplicationContext中
//这个方法是Spring中加载Bean的核心方法，SpringBoot也用它进行类的自动装配、注册、解析、注入
//Tomcat的启动，WebApplicationContext的初始化
------------
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
//刷新上下文环境，初始化上下文环境，对系统的环境变量或者系统属性进行准备和校验
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
//初始化beanfactory，解析xml，相当于之前的xmlBeanfactory操作
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
//为上下文准备beanfactory，对beanFactory的各种功能进行填充，如@autowired，设置spel表达式解析器，设置编辑注册器，添加applicationContextAwareprocessor处理器等等
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
//提供子类覆盖的额外处理，即子类处理自定义的beanfactorypostProcess
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
//激活各种beanfactory处理器
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
//注册拦截bean创建的bean处理器，即注册beanPostProcessor
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
//初始化上下文中的资源文件如国际化文件的处理
initMessageSource();
// Initialize event multicaster for this context.
//初始化上下文事件广播器
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
//给子类扩展初始化其他bean
onRefresh();
// Check for listener beans and register them.
//在所有的bean中查找listener bean,然后 注册到广播器中
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//初始化剩余的非懒惰的bean，即初始化非延迟加载的bean
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
//发完成刷新过程，通知声明周期处理器刷新过程，同时发出ContextRefreshEvent通知别人
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}12、应用上下文刷新后置处理
afterRefresh(context, applicationArguments);
//当前方法的代码是空的，可以做一些自定义的后置处理操作
protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) {
}13、停止计时监控类：
计时监听器停止，并统计一些任务执行信息
stopWatch.stop();
public void stop() throws IllegalStateException {
if (this.currentTaskName == null) {
throw new IllegalStateException("Can't stop StopWatch: it's not running");
}
long lastTime = System.nanoTime() - this.startTimeNanos;
this.totalTimeNanos += lastTime;
this.lastTaskInfo = new TaskInfo(this.currentTaskName, lastTime);
if (this.keepTaskList) {
this.taskList.add(this.lastTaskInfo);
}
++this.taskCount;
this.currentTaskName = null;
}14、输出日志记录执行主类名、时间信息
Started StarterApplication in 133.565 seconds (JVM running for 136.989)
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}15、发布应用上下文启动完成事件
触发所有SpringapplicationRunListener监听器的started事件方法，如果启动异常发布异常事件
listeners.started(context);
void started(ConfigurableApplicationContext context) {
for (SpringApplicationRunListener listener : this.listeners) {
listener.started(context);
}
}16、执行所有Runner执行器
执行所有applicationRunner和CommandLineRunner两种运行器
callRunners(context, applicationArguments);
private void callRunners(ApplicationContext context, ApplicationArguments args) {
List<Object> runners = new ArrayList<>();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
for (Object runner : new LinkedHashSet<>(runners)) {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
}
}17、发布应用上下文就绪事件
触发所有springapplicationRunnListener的running事件方法
listeners.running(context);
void running(ConfigurableApplicationContext context) {
for (SpringApplicationRunListener listener : this.listeners) {
listener.running(context);
}
}18、返回应用上下文
return context;
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