幾個重要的事件回調機制
配置在 META-INF/spring.factories
- ApplicationContextInitializer
- SpringApplicationRunListener
只需要放在 IOC 容器中
- ApplicationRunner
- CommandLineRunner
啓動流程:
1、創建 SpringApplication 對象
initialize(sources);
private void initialize(Object[] sources) {
//保存主配置類
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));
}
//判斷當前是否一個web應用
this.webEnvironment = deduceWebEnvironment();
//從類路徑下找到META-INF/spring.factories配置的所有ApplicationContextInitializer;然後保存起來
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
//從類路徑下找到ETA-INF/spring.factories配置的所有ApplicationListener
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
//從多個配置類中找到有main方法的主配置類
this.mainApplicationClass = deduceMainApplicationClass();
}
2、運行 run 方法
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
configureHeadlessProperty();
//獲取SpringApplicationRunListeners;從類路徑下META-INF/spring.factories
SpringApplicationRunListeners listeners = getRunListeners(args);
//回調所有的獲取SpringApplicationRunListener.starting()方法
listeners.starting();
try {
//封裝命令行參數
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
//準備環境
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
//創建環境完成後回調SpringApplicationRunListener.environmentPrepared();表示環境準備完成
Banner printedBanner = printBanner(environment);
//創建ApplicationContext;決定創建web的ioc還是普通的ioc
context = createApplicationContext();
analyzers = new FailureAnalyzers(context);
//準備上下文環境;將environment保存到ioc中;而且applyInitializers();
//applyInitializers():回調之前保存的所有的ApplicationContextInitializer的initialize方法
//回調所有的SpringApplicationRunListener的contextPrepared();
//
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
//prepareContext運行完成以後回調所有的SpringApplicationRunListener的contextLoaded();
//刷新容器;ioc容器初始化(如果是web應用還會創建嵌入式的Tomcat);
//掃描,創建,加載所有組件的地方;(配置類,組件,自動配置)
refreshContext(context);
//從ioc容器中獲取所有的ApplicationRunner和CommandLineRunner進行回調
//ApplicationRunner先回調,CommandLineRunner再回調
afterRefresh(context, applicationArguments);
//所有的SpringApplicationRunListener回調finished方法
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
//整個SpringBoot應用啓動完成以後返回啓動的ioc容器;
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers, ex);
throw new IllegalStateException(ex);
}
}