SpringBoot启动过程源码解析
一、启动配置原理
几个重要的事件回调机制
配置在META-INF/spring.factories
ApplicationContextInitializer
SpringApplicationRunListener
只需要放在ioc容器中
ApplicationRunner
CommandLineRunner
启动流程：断点启动Spring boot应用
1、下一步进入SpringApplication.run()中，此方法分为2个步骤
public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
return new SpringApplication(sources).run(args); //sources为主运行类的信息
}
第一步：创建SpringApplication对象
第二步：运行run(); static ConfigurableApplicationContext run(Object[] sources, String[] args) {
return new SpringApplication(sources).run(args); //sources为主运行类的信息
}
第一步：创建SpringApplication对象
第二步：运行run();1.1 第一步SpringApplication创建
初始化参数，执行SpringApplication()方法
public SpringApplication(Object... sources) {
initialize(sources);
} SpringApplication(Object... sources) {
initialize(sources);
}1.1.1 执行SpringApplication.initialize（）
private void initialize(Object[] sources) {
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));//保存主配置类
}
//判断是否为web应用，通过classLoader判断是否加载的有{ "javax.servlet.Servlet",
"org.springframework.web.context.ConfigurableWebApplicationContext" }
this.webEnvironment = deduceWebEnvironment();
//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer；然后保存起来
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
//从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListener
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();//获取到main方法所在的类
} void initialize(Object[] sources) {
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));//保存主配置类
}
//判断是否为web应用，通过classLoader判断是否加载的有{ "javax.servlet.Servlet",
"org.springframework.web.context.ConfigurableWebApplicationContext" }
this.webEnvironment = deduceWebEnvironment();
//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer；然后保存起来
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
//从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListener
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();//获取到main方法所在的类
}1.1.1.1 创建ApplicationContextInitializer
getSpringFactoriesInstances（）说明： loadFactoryNames()获取需要加载的类
private <T> Collection extends T> getSpringFactoriesInstances(Class<T> type,
Class[] parameterTypes, Object... args) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
// 通过classLoader 从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer集合，
Set<String> names = new LinkedHashSet<String>(
SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes,
classLoader, args, names); //创建实例
AnnotationAwareOrderComparator.sort(instances); //排序
return instances;
} <T> Collection extends T> getSpringFactoriesInstances(Class<T> type,
Class[] parameterTypes, Object... args) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
// 通过classLoader 从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer集合，
Set<String> names = new LinkedHashSet<String>(
SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes,
classLoader, args, names); //创建实例
AnnotationAwareOrderComparator.sort(instances); //排序
return instances;
}
1.1.1.1.1 执行 SpringFactoriesLoader.loadFactoryNames（）
说明：主要执行SpringFactoriesLoader.loadFactoryNames(type, classLoader)，通过classLoader 从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer
//获取ApplicationContextInitializer 保存起来
public static List<String> loadFactoryNames(Class factoryClass, ClassLoader classLoader) {
String factoryClassName = factoryClass.getName();
try {
//获取所有jar下面的META-INF/spring.factories 文件路径
//例如： jar:file:/C:/Users/Administrator/.m2/repository/org/springframework/boot/spring-boot/1.5.10.RELEASE/spring-boot-1.5.10.RELEASE.jar!/META-INF/spring.factories
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));
//读取配置文件中的ApplicationContextInitializer
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);
}
}
public static List<String> loadFactoryNames(Class factoryClass, ClassLoader classLoader) {
String factoryClassName = factoryClass.getName();
try {
//获取所有jar下面的META-INF/spring.factories 文件路径
//例如： jar:file:/C:/Users/Administrator/.m2/repository/org/springframework/boot/spring-boot/1.5.10.RELEASE/spring-boot-1.5.10.RELEASE.jar!/META-INF/spring.factories
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));
//读取配置文件中的ApplicationContextInitializer
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);
}
}
获取的ApplicationContextInitializer
1.1.1.2 创建ApplicationListener
执行setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class)); 和ApplicationContextInitializer操作一样；
从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListener
获取的ApplicationListener 如下：
1.1.1.3 获取配置类main()
从多个配置类中哪个类中有main（）的主配置类
this.mainApplicationClass = deduceMainApplicationClass();private Class deduceMainApplicationClass() {
try {
StackTraceElement[] stackTrace = new RuntimeException().getStackTrace();
for (StackTraceElement stackTraceElement : stackTrace) {
if ("main".equals(stackTraceElement.getMethodName())) { //判断是否包含main方法
return Class.forName(stackTraceElement.getClassName());
}
}
}
catch (ClassNotFoundException ex) {
// Swallow and continue
}
return null;
} Class deduceMainApplicationClass() {
try {
StackTraceElement[] stackTrace = new RuntimeException().getStackTrace();
for (StackTraceElement stackTraceElement : stackTrace) {
if ("main".equals(stackTraceElement.getMethodName())) { //判断是否包含main方法
return Class.forName(stackTraceElement.getClassName());
}
}
}
catch (ClassNotFoundException ex) {
// Swallow and continue
}
return null;
}1.1.1.4 初始化结束
画圈为initialize（）方法执行保存结果，和webEnvironment
QQ截图
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1.2 SpringApplication.run()方法
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch(); //开始起止的监听
stopWatch.start();
ConfigurableApplicationContext context = null; //声明IOC容器
FailureAnalyzers analyzers = null;
configureHeadlessProperty();//awt 相关，省略
//获取SpringApplicationRunListeners；从类路径下META-INF/spring.factories
//得到一个org.springframework.boot.context.event.EventPublishingRunListener
SpringApplicationRunListeners listeners = getRunListeners(args);
//回调所有的获取SpringApplicationRunListener.starting()方法
listeners.starting(); //启动
try {
//封装命令行参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
//准备环境
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
Banner printedBanner = printBanner(environment); //控制台打印Spring banner图标
//创建ApplicationContext；决定创建web的ioc还是普通的ioc
context = createApplicationContext();
analyzers = new FailureAnalyzers(context); //做异常处理报告用
//准备上下文环境;将environment保存到ioc中；而且applyInitializers()；
//applyInitializers()：回调之前保存的所有的ApplicationContextInitializer的initialize方法
//回调所有的SpringApplicationRunListener的contextPrepared()；
//prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded（）；
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
//刷新容器；ioc容器初始化（如果是web应用还会创建嵌入式的Tomcat）；Spring注解版
//扫描，创建，加载所有组件的地方；（配置类，组件，自动配置）
refreshContext(context); //IOC创建完成
//从ioc容器中获取所有的ApplicationRunner和CommandLineRunner进行回调
//ApplicationRunner先回调，CommandLineRunner再回调
afterRefresh(context, applicationArguments);
//所有的SpringApplicationRunListener回调finished方法
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
//整个SpringBoot应用启动完成以后返回启动的ioc容器；
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers, ex);
throw new IllegalStateException(ex);
}
} ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch(); //开始起止的监听
stopWatch.start();
ConfigurableApplicationContext context = null; //声明IOC容器
FailureAnalyzers analyzers = null;
configureHeadlessProperty();//awt 相关，省略
//获取SpringApplicationRunListeners；从类路径下META-INF/spring.factories
//得到一个org.springframework.boot.context.event.EventPublishingRunListener
SpringApplicationRunListeners listeners = getRunListeners(args);
//回调所有的获取SpringApplicationRunListener.starting()方法
listeners.starting(); //启动
try {
//封装命令行参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
//准备环境
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
Banner printedBanner = printBanner(environment); //控制台打印Spring banner图标
//创建ApplicationContext；决定创建web的ioc还是普通的ioc
context = createApplicationContext();
analyzers = new FailureAnalyzers(context); //做异常处理报告用
//准备上下文环境;将environment保存到ioc中；而且applyInitializers()；
//applyInitializers()：回调之前保存的所有的ApplicationContextInitializer的initialize方法
//回调所有的SpringApplicationRunListener的contextPrepared()；
//prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded（）；
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
//刷新容器；ioc容器初始化（如果是web应用还会创建嵌入式的Tomcat）；Spring注解版
//扫描，创建，加载所有组件的地方；（配置类，组件，自动配置）
refreshContext(context); //IOC创建完成
//从ioc容器中获取所有的ApplicationRunner和CommandLineRunner进行回调
//ApplicationRunner先回调，CommandLineRunner再回调
afterRefresh(context, applicationArguments);
//所有的SpringApplicationRunListener回调finished方法
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
//整个SpringBoot应用启动完成以后返回启动的ioc容器；
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers, ex);
throw new IllegalStateException(ex);
}
}1.2.1 获取环境prepareEnvironment（）
private ConfigurableEnvironment prepareEnvironment(
SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// 创建 或者 配置 the 环境
ConfigurableEnvironment environment = getOrCreateEnvironment();
// 配置环境
configureEnvironment(environment, applicationArguments.getSourceArgs());
//创建环境完成后回调SpringApplicationRunListener.environmentPrepared()；表示环境准备完成
listeners.environmentPrepared(environment);
if (!this.webEnvironment) {
environment = new EnvironmentConverter(getClassLoader())
.convertToStandardEnvironmentIfNecessary(environment);
}
return environment;
}
ConfigurableEnvironment prepareEnvironment(
SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// 创建 或者 配置 the 环境
ConfigurableEnvironment environment = getOrCreateEnvironment();
// 配置环境
configureEnvironment(environment, applicationArguments.getSourceArgs());
//创建环境完成后回调SpringApplicationRunListener.environmentPrepared()；表示环境准备完成
listeners.environmentPrepared(environment);
if (!this.webEnvironment) {
environment = new EnvironmentConverter(getClassLoader())
.convertToStandardEnvironmentIfNecessary(environment);
}
return environment;
}
1.2.2 准备上下文环境 prepareContext（）
private void prepareContext(ConfigurableApplicationContext context,
ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments, Banner printedBanner) {
context.setEnvironment(environment); //给IOC容器赋值environment
postProcessApplicationContext(context); //IOC后置处理，注册了组件
applyInitializers(context); //回调之前保存的所有的ApplicationContextInitializer的initialize方法
listeners.contextPrepared(context);//执行所有Listeners的contextPrepared()方法
if (this.logStartupInfo) { //日志记录
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// 把命令行参数的类applicationArguments 注册到IOC容器
context.getBeanFactory().registerSingleton("springApplicationArguments",
applicationArguments);
if (printedBanner != null) {
//注册打印的banner
context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
}
// 获取主类信息
Set<Object> sources = getSources();
Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[sources.size()]));
//prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded（）；
listeners.contextLoaded(context);
} void prepareContext(ConfigurableApplicationContext context,
ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments, Banner printedBanner) {
context.setEnvironment(environment); //给IOC容器赋值environment
postProcessApplicationContext(context); //IOC后置处理，注册了组件
applyInitializers(context); //回调之前保存的所有的ApplicationContextInitializer的initialize方法
listeners.contextPrepared(context);//执行所有Listeners的contextPrepared()方法
if (this.logStartupInfo) { //日志记录
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// 把命令行参数的类applicationArguments 注册到IOC容器
context.getBeanFactory().registerSingleton("springApplicationArguments",
applicationArguments);
if (printedBanner != null) {
//注册打印的banner
context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
}
// 获取主类信息
Set<Object> sources = getSources();
Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[sources.size()]));
//prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded（）；
listeners.contextLoaded(context);
}
1.2.2.1 准备上下文环境 applyInitializers（）
getInitializers() ；获取到之前获取的ApplicationContextInitializer 实例，执行initialize（）方法
protected void applyInitializers(ConfigurableApplicationContext context) {
for (ApplicationContextInitializer initializer : getInitializers()) {
Class requiredType = GenericTypeResolver.resolveTypeArgument(
initializer.getClass(), ApplicationContextInitializer.class);
Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");
initializer.initialize(context);
}
} void applyInitializers(ConfigurableApplicationContext context) {
for (ApplicationContextInitializer initializer : getInitializers()) {
Class requiredType = GenericTypeResolver.resolveTypeArgument(
initializer.getClass(), ApplicationContextInitializer.class);
Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");
initializer.initialize(context);
}
}
1.2.3 刷新容器refreshContext(context);
刷新容器；ioc容器初始化（如果是web应用还会创建嵌入式的Tomcat）；Spring注解版 扫描，创建，加载所有组件的地方；（配置类，组件，自动配置）
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 准备此上下文以进行刷新。
prepareRefresh();
// 告诉子类刷新内部bean工厂。
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//准备使用这个beanFatory
//配置工厂的标准上下文特性，
//*如上下文的类加载器和后置处理器。
prepareBeanFactory(beanFactory);
try {
// 允许在上下文子类中对bean工厂进行后处理。
postProcessBeanFactory(beanFactory);
// 调用工厂处理器在上下文中注册为bean。
invokeBeanFactoryPostProcessors(beanFactory);
// 注册bean处理器，拦截bean创建。
registerBeanPostProcessors(beanFactory);
// 初始化此上下文的消息源。
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
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();
}
}
} void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 准备此上下文以进行刷新。
prepareRefresh();
// 告诉子类刷新内部bean工厂。
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//准备使用这个beanFatory
//配置工厂的标准上下文特性，
//*如上下文的类加载器和后置处理器。
prepareBeanFactory(beanFactory);
try {
// 允许在上下文子类中对bean工厂进行后处理。
postProcessBeanFactory(beanFactory);
// 调用工厂处理器在上下文中注册为bean。
invokeBeanFactoryPostProcessors(beanFactory);
// 注册bean处理器，拦截bean创建。
registerBeanPostProcessors(beanFactory);
// 初始化此上下文的消息源。
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
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();
}
}
}1.2.4 调用SpringApplication.afterRefresh（）
afterRefresh(context, applicationArguments);
protected void afterRefresh(ConfigurableApplicationContext context,
ApplicationArguments args) {
callRunners(context, args);
}
//获取ApplicationRunner 和 CommandLineRunner 并会调
private void callRunners(ApplicationContext context, ApplicationArguments args) {
List<Object> runners = new ArrayList<Object>();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
for (Object runner : new LinkedHashSet<Object>(runners)) {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
}
} void afterRefresh(ConfigurableApplicationContext context,
ApplicationArguments args) {
callRunners(context, args);
}
//获取ApplicationRunner 和 CommandLineRunner 并会调
private void callRunners(ApplicationContext context, ApplicationArguments args) {
List<Object> runners = new ArrayList<Object>();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
for (Object runner : new LinkedHashSet<Object>(runners)) {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
}
}Springboot整合例子：https://github.com/spring-projects/spring-boot/tree/master/spring-boot-samples