011-Spring Boot 运行流程分析SpringApplication.run

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