一、启动原理
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
SpringApplication.run(主程序类)
– new SpringApplication(主程序类)- • 判断是否web应用
- • 加载并保存所有ApplicationContextInitializer（META-INF/spring.factories），
- • 加载并保存所有ApplicationListener
- • 获取到主程序类
- • 回调所有的SpringApplicationRunListener（META-INF/spring.factories）的starting
- • 获取ApplicationArguments
- • 准备环境&回调所有监听器（ SpringApplicationRunListener ）的environmentPrepared
- • 打印banner信息
- • 创建ioc容器对象（
– AnnotationConfigApplicationContext（普通环境容器）
– run()
- • 准备环境
– 监听器SpringApplicationRunListener回调contextPrepared
– 加载主配置类定义信息
– 监听器SpringApplicationRunListener回调contextLoaded
- • 刷新启动IOC容器；
– 包括从META-INF/spring.factories中获取的所有EnableAutoConfiguration组件
- • 回调容器中所有的ApplicationRunner、CommandLineRunner的run方法
- • 监听器SpringApplicationRunListener回调finished
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();
}
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));
}
}
二、自动配置
• Spring Boot启动扫描所有jar包的META-INF/spring.factories中配置的
EnableAutoConfiguration组件
• spring-boot-autoconfigure.jar\META-INF\spring.factories有启动时需要加载的
EnableAutoConfiguration组件配置
• 配置文件中使用debug=true可以观看到当前启用的自动配置的信息
• 自动配置会为容器中添加大量组件
• Spring Boot在做任何功能都需要从容器中获取这个功能的组件
• Spring Boot 总是遵循一个标准；容器中有我们自己配置的组件就用我们配置的，没有就用自动配
置默认注册进来的组件；