SpringApplication实例化

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
    this.resourceLoader = resourceLoader;
    Assert.notNull(primarySources, "PrimarySources must not be null");
    this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
    //根据classpath下面的类来推断当前是哪种类型的应用，非web应用，web应用，还是reactive应用
    this.webApplicationType = WebApplicationType.deduceFromClasspath();
    //从META-INF/spring.factories配置文件中加载ApplicationContextInitializer初始化器
    setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
    //从META-INF/spring.factories配置文件中加载ApplicationListener监听器
    setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    //推断主程序类
    this.mainApplicationClass = deduceMainApplicationClass();
}

SpringApplication.run

public ConfigurableApplicationContext run(String... args) {
    StopWatch stopWatch = new StopWatch();
    stopWatch.start();
    ConfigurableApplicationContext context = null;
    Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
    configureHeadlessProperty();
    //获取事件监听器，在后续的特定节点中发布事件让监听器监听到，参考：https://qigangzhong.github.io/2019/12/17/spring-event/
    SpringApplicationRunListeners listeners = getRunListeners(args);
    listeners.starting();
    try {
        ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
        //获取环境信息，此处解析application.properties文件
        ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
        configureIgnoreBeanInfo(environment);
        Banner printedBanner = printBanner(environment);
        context = createApplicationContext();
        exceptionReporters = getSpringFactoriesInstances(
                SpringBootExceptionReporter.class,
                new Class[] { ConfigurableApplicationContext.class }, context);
        prepareContext(context, environment, listeners, applicationArguments,
                printedBanner);
        refreshContext(context);
        afterRefresh(context, applicationArguments);
        stopWatch.stop();
        if (this.logStartupInfo) {
            new StartupInfoLogger(this.mainApplicationClass)
                    .logStarted(getApplicationLog(), stopWatch);
        }
        listeners.started(context);
        callRunners(context, applicationArguments);
    }
    catch (Throwable ex) {
        handleRunFailure(context, ex, exceptionReporters, listeners);
        throw new IllegalStateException(ex);
    }

    try {
        listeners.running(context);
    }
    catch (Throwable ex) {
        handleRunFailure(context, ex, exceptionReporters, null);
        throw new IllegalStateException(ex);
    }
    return context;
}

SpringApplicationRunListener

获取事件监听器，在后续的特定节点中发布事件让监听器监听到，参考：SpringApplicationRunListener

prepareEnvironment

private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) {
    // Create and configure the environment
    ConfigurableEnvironment environment = getOrCreateEnvironment();
    configureEnvironment(environment, applicationArguments.getSourceArgs());
    listeners.environmentPrepared(environment);
    bindToSpringApplication(environment);
    if (!this.isCustomEnvironment) {
        environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment, deduceEnvironmentClass());
    }
    ConfigurationPropertySources.attach(environment);
    return environment;
}

environment有三种类型

  • StandardServletEnvironment
  • StandardEnvironment
  • StandardReactiveWebEnvironment

Environment.png

参考