SpringBoot启动配置原理
https://cloud.tencent.com/developer/article/1802822?from=article.detail.1449134
# SpringBoot启动配置原理
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
启动流程:
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();
}
![](https://ask.qcloudimg.com/http-save/7517959/b1xvkx24rv.png?imageView2/2/w/1620)
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));
}
}