启动配置原理

几个重要的事件回调机制

配置在META-INF/spring.facotries

ApplicationContextInitializer

SpringApplicationRunListener

只需要放在ioc容器中

ApplicationRunner

CommandLineRunner

启动流程(Springboot 1.5.9)

1，创建SpringApplication对象

initialize(sources);
private void initialize(Object[] sources) {
    //保存主配置类
    if (sources != null && sources.length > 0) {
        this.sources.addAll(Arrays.asList(sources));
    }
    //判断当前是否一个web应用
    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));
    //从多个配置类中找到有main方法的主配置类
    this.mainApplicationClass = deduceMainApplicationClass();
}

 2，运行run方法

public ConfigurableApplicationContext run(String... args) {
    StopWatch stopWatch = new StopWatch();
    stopWatch.start();
    ConfigurableApplicationContext context = null;
    FailureAnalyzers analyzers = null;
    configureHeadlessProperty();
    //获取SpringApplicationRunListeners；从类路径下META‐INF/spring.factories
    SpringApplicationRunListeners listeners = getRunListeners(args);
    //回调所有的获取SpringApplicationRunListener.starting()方法
    listeners.starting();
    try {
        //封装命令行参数
        ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                args);
        //准备环境
        ConfigurableEnvironment environment = prepareEnvironment(listeners,
                applicationArguments);
        //创建环境完成后回调SpringApplicationRunListener.environmentPrepared()；表示环境准备完成
        Banner printedBanner = printBanner(environment);
        //创建ApplicationContext；决定创建web的ioc还是普通的ioc
        context = createApplicationContext();
        analyzers = new FailureAnalyzers(context);
        //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(context, environment, listeners, applicationArguments,
                printedBanner);
         //prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded（）；
        //s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);
         //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);
    }
}

3，事件监听机制

配置在META-INF/spring.factories

ApplicationContextInitializer

public class HelloApplicationContextInitializer implements
        ApplicationContextInitializer<ConfigurableApplicationContext> {
    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        System.out.println("ApplicationContextInitializer...initialize..."+applicationContext);
    }
}

SpringApplicationRunListener

public class HelloSpringApplicationRunListener implements SpringApplicationRunListener {
    //必须有的构造器
    public HelloSpringApplicationRunListener(SpringApplication application, String[] args){
    }
    @Override
    public void starting() {
        System.out.println("SpringApplicationRunListener...starting...");
    }
    @Override
    public void environmentPrepared(ConfigurableEnvironment environment) {
        Object o = environment.getSystemProperties().get("os.name");
        System.out.println("SpringApplicationRunListener...environmentPrepared.."+o);
    }
    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener...contextPrepared...");
    }
    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener...contextLoaded...");
    }
    @Override
    public void finished(ConfigurableApplicationContext context, Throwable exception) {
        System.out.println("SpringApplicationRunListener...finished...");
    }
}

配置（META-INF/spring.factories）

org.springframework.context.ApplicationContextInitializer=\
com.atguigu.springboot.listener.HelloApplicationContextInitializer
org.springframework.boot.SpringApplicationRunListener=\
com.atguigu.springboot.listener.HelloSpringApplicationRunListener

只需要放在ioc容器中

ApplicationRunner

@Component
public class HelloApplicationRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.println("ApplicationRunner...run....");
    }
}

CommandLineRunner

@Component
public class HelloCommandLineRunner implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("CommandLineRunner...run..."+ Arrays.asList(args));
    }
}