SpringBoot启动流程
我们从SpringBoot的主方法的run方法进去一探究竟
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run方法进去以后做了两件事
- 创建SpringApplication类
- 执行run方法。
public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
return new SpringApplication(sources).run(args);
}创建SpringApplication对象
调用initialize(sources)方法创建对象private void initialize(Object[] sources) {
//保存主配置类
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));
}
//判断当前应用是不是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,配置类可以是多个。
this.mainApplicationClass = deduceMainApplicationClass();
}//这样将SpringApplication对象创建出来运行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);
//prepareEnvironment中:listeners.environmentPrepared(environment);
//创建环境完成后回调SpringApplicationRunListener.environmentPrepared();表示环境准备完成
Banner printedBanner = printBanner(environment);//打印Spring的图标
context = createApplicationContext();//创建IOC容器,决定创建web的ioc还是普通的ioc
analyzers = new FailureAnalyzers(context);//出现异常做异常分析报告的
//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);
//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);
listeners.finished(context, null);//所有的SpringApplicationRunListener回调finished方法
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);
}
}
关于几个重要的事件回调机制
配置在META-INF/spring.factories
ApplicationContextInitializer
SpringApplicationRunListener
只需要放在ioc容器中
ApplicationRunner
CommandLineRunner
ApplicationContextInitializer
public class HelloApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { |
SpringApplicationRunListener
public class HelloSpringApplicationRunListener implements SpringApplicationRunListener { |
配置让监听器起作用,在(META-INF/spring.factories)文件夹下进行配置,没有这个文件夹就在资源文件下新建一个。
\ = |
ApplicationRunner
只需要放在ioc容器中
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CommandLineRunner
只需要放在ioc容器中
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