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

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