一、程序入口
1.1、静态方法
//直接调用run方法
ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
内部实现：
public static ConfigurableApplicationContext run(Object source, String... args) {
return run(new Object[] { source }, args);
}
查看run
public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
return new SpringApplication(sources).run(args);
}
故等效于实例化，后调用。同1.2
1.2、实例化SpringApplication，调用run方法
//实例化SpringApplication然后调用run方法
SpringApplication application = new SpringApplication(App.class);
ConfigurableApplicationContext context = application.run(args);
查看实现
public SpringApplication(Object... sources) {
initialize(sources);
}
查看initialize
@SuppressWarnings({ "unchecked", "rawtypes" })
private void initialize(Object[] sources) {
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));
}
this.webEnvironment = deduceWebEnvironment();
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();
}
二、运行流程分析
2.1、【new SpringApplication(App.class);初始化】
1、将source添加到set：中：this.sources.addAll(Arrays.asList(sources));
2、判断是不是web环境this.webEnvironment = deduceWebEnvironment();
private boolean deduceWebEnvironment() {
for (String className : WEB_ENVIRONMENT_CLASSES) {
if (!ClassUtils.isPresent(className, null)) {
return false;
}
}
return true;
}
内部
private static final String[] WEB_ENVIRONMENT_CLASSES = { "javax.servlet.Servlet","org.springframework.web.context.ConfigurableWebApplicationContext" };
3、加载所有classpath下面的META-INF/spring.factoriesd的ApplicationContextInitializer, getSpringFactoriesInstances(ApplicationContextInitializer.class)
将所有的ApplicationContextInitializer放置到：private List<ApplicationContextInitializer<?>> initializers;中：
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
4、listener同3一致
加载所有classpath下面的META-INF/spring.factories的ApplicationListener, getSpringFactoriesInstances(ApplicationListener.class)
将所有的ApplicationListener放置到：private List<ApplicationListener<?>> listeners;中：
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
5、推断main方法所在的类
是this.mainApplicationClass = deduceMainApplicationClass();
2.2、【run方法】
6、开始执行run方法
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
analyzers = new FailureAnalyzers(context);
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
refreshContext(context);
afterRefresh(context, applicationArguments);
listeners.finished(context, null);
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);
}
}
时间监视器
StopWatch stopWatch = new StopWatch();
stopWatch.start();
stopWatch.stop();
7、设置java.awt.headless系统变量
ConfigurableApplicationContext context = null;
configureHeadlessProperty();
注意：新增FailureAnalyzers analyzers = null;
是为了失败分析调试时使用
FailureAnalyzers analyzers = null;
analyzers = new FailureAnalyzers(context);
8、加载所有classpath下面的META-INF/spring.factories，SpringApplicationRunListeners
执行所有SpringApplicationRunListeners的所有started方法
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
作用：SpringApplicationRunListeners是Springboot扩展点。
用来在执行过程中，不同的时间点来进行发送事件通知的。
9、实例化ApplicationArguments参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
10、创建ConfigurableEnvironment
ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
内部
private ConfigurableEnvironment prepareEnvironment(
SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment();
configureEnvironment(environment, applicationArguments.getSourceArgs());
listeners.environmentPrepared(environment);
if (!this.webEnvironment) {
environment = new EnvironmentConverter(getClassLoader())
.convertToStandardEnvironmentIfNecessary(environment);
}
return environment;
}
创建：ConfigurableEnvironment environment = getOrCreateEnvironment();
配置：configureEnvironment(environment, applicationArguments.getSourceArgs());
主要是把run方法的参数配置到environment
监听：listeners.environmentPrepared(environment);
执行所有SpringApplicationRunListeners的所有environmentPrepared方法
非web环境转换
if (!this.webEnvironment) {
environment = new EnvironmentConverter(getClassLoader())
.convertToStandardEnvironmentIfNecessary(environment);
}
11、打印Banner：Banner printedBanner = printBanner(environment);
12、创建ConfigurableApplicationContext：context = createApplicationContext();
protected ConfigurableApplicationContext createApplicationContext() {
Class<?> contextClass = this.applicationContextClass;
if (contextClass == null) {
try {
contextClass = Class.forName(this.webEnvironment
? DEFAULT_WEB_CONTEXT_CLASS : DEFAULT_CONTEXT_CLASS);
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Unable create a default ApplicationContext, "
+ "please specify an ApplicationContextClass",
ex);
}
}
return (ConfigurableApplicationContext) BeanUtils.instantiate(contextClass);
}
如果是WEB环境，实例化：org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext
否则实例化：org.springframework.context.annotation.AnnotationConfigApplicationContext
13、准备context：prepareContext(context, environment, listeners, applicationArguments,printedBanner);
内部
private void prepareContext(ConfigurableApplicationContext context,
ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments, Banner printedBanner) {
context.setEnvironment(environment);
postProcessApplicationContext(context);
applyInitializers(context);
listeners.contextPrepared(context);
if (this.logStartupInfo) {
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
} // Add boot specific singleton beans
context.getBeanFactory().registerSingleton("springApplicationArguments",
applicationArguments);
if (printedBanner != null) {
context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
} // Load the sources
Set<Object> sources = getSources();
Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[sources.size()]));
listeners.contextLoaded(context);
}
a、设置setEnvironment
b、后置调用：postProcessApplicationContext(context);
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());
}
}
}
如果beanNameGenerator不为空，就把beanNameGenerator对象注入到context里面去，、
同样如果resourceLoader不为空，就设置：setResourceLoader、setClassLoader
c、回调所有的ApplicationContextInitializer：applyInitializers
@SuppressWarnings({ "rawtypes", "unchecked" })
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);
}
}
d、执行所有SpringApplicationRunListeners的contextPrepared方法：listeners.contextPrepared(context);
e、日志输出
f、依次向Spring容器中注入springApplicationArguments、Banners对象
context.getBeanFactory().registerSingleton("springApplicationArguments",
applicationArguments);
if (printedBanner != null) {
context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
}
g、将所有的source加载到context中，类似于初始化一个AnnotationConfigApplicationContext然后将所有的容器注入
Set<Object> sources = getSources();
Assert.notEmpty(sources, "Sources must not be empty");
load(context, sources.toArray(new Object[sources.size()]));
h、执行所有SpringApplicationRunListeners的contextLoaded方法：listeners.contextLoaded(context);
14、执行refreshContext(context);方法，并且判断调用registerShutdownHook
private void refreshContext(ConfigurableApplicationContext context) {
refresh(context);
if (this.registerShutdownHook) {
try {
context.registerShutdownHook();
}
catch (AccessControlException ex) {
// Not allowed in some environments.
}
}
}
15、afterRefresh(context, applicationArguments);回调，获取容器中所有的ApplicationRunner、CommandLineRunner接口，然后排序，依次调用
protected void afterRefresh(ConfigurableApplicationContext context,
ApplicationArguments args) {
callRunners(context, args);
} 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);
}
}
} private void callRunner(ApplicationRunner runner, ApplicationArguments args) {
try {
(runner).run(args);
}
catch (Exception ex) {
throw new IllegalStateException("Failed to execute ApplicationRunner", ex);
}
} private void callRunner(CommandLineRunner runner, ApplicationArguments args) {
try {
(runner).run(args.getSourceArgs());
}
catch (Exception ex) {
throw new IllegalStateException("Failed to execute CommandLineRunner", ex);
}
}
16、执行所有SpringApplicationRunListeners的finished方法：listeners.finished(context, null);;
17、结束，如果出现问题将使用日志handleRunFailure