public static ConfigurableApplicationContext run(Object[] sources, String[] args) {
return new SpringApplication(sources).run(args);
}
1、启动流程:
1、创建SpringApplication对象(new SpringApplication(sources))
通过构造器调用initialize(sources);方法
public SpringApplication(Object... sources) {
initialize(sources);
}
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();
}
①setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class)):
从类路径下的META-INF/spring.factories中拿到配置的所有ApplicationContextInitializer
例子:
方法执行完成后,拿到的所有的Initializers:
②setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));:
从类路径下META-INF/spring.factories拿到配置的所有ApplicationListener
例子:方法执行完成后,拿到的所有的Listener:
2、运行run方法(.run(args))
run方法:
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//声明一个ioc容器
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();
//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);
//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);
}
}
步骤的解析:
1)、SpringApplicationRunListeners listeners = getRunListeners(args);:
获取SpringApplicationRunListeners,从类路径下META-INF/spring.factories
2)、listeners.starting();
回调所有的SpringApplicationRunListener.starting()方法
3)、new DefaultApplicationArguments(args);
封装命令行参数
4)、prepareEnvironment(listeners,applicationArguments);
创建环境完成后回调SpringApplicationRunListener.environmentPrepared();表示环境准备完成
5)、printBanner(environment);
打印spring图标
6)、createApplicationContext();
创建ApplicationContext,决定创建web的ioc还是普通的ioc
7)、prepareContext(context, environment, listeners, applicationArguments,printedBanner);
准备上下文环境,将environment保存到ioc中,而且调用了applyInitializers();
① applyInitializers();
回调之前保存的所有的ApplicationContextInitializer的initialize()方法
然后回调SpringApplicationRunListener.contextPrepared(context);方法,
运行到最后一步回调SpringApplicationRunListener.contextLoaded(context);方法
8)、 refreshContext(context);
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)
9)、 afterRefresh(context, applicationArguments);
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
10)、listeners.finished(context, null);
所有的SpringApplicationRunListener回调finished()方法
11)、 return context;
整个spring boot应用启动完成后,返回ioc容器
2、事件监听机制
在spring boot应用启动中有几个重要的事件回调机制
1.配置在META-INF/spring.factories
1)ApplicationContextInitializer
public class HelloApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
System.out.println("HelloApplicationContextInitializer.........initialize" + applicationContext);
}
}
2)SpringApplicationRunListener(必须要有一个(SpringApplication application, String[] args)参数的构造器,否则会出错)
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("HelloSpringApplicationRunListener...starting");
}
@Override
public void environmentPrepared(ConfigurableEnvironment environment) {
System.out.println("HelloSpringApplicationRunListener...environmentPrepared");
}
@Override
public void contextPrepared(ConfigurableApplicationContext context) {
System.out.println("HelloSpringApplicationRunListener...contextPrepared");
}
@Override
public void contextLoaded(ConfigurableApplicationContext context) {
System.out.println("HelloSpringApplicationRunListener...contextLoaded");
}
@Override
public void finished(ConfigurableApplicationContext context, Throwable exception) {
System.out.println("HelloSpringApplicationRunListener...finished");
}
}
在META-INF中的spring.factories中配置
org.springframework.context.ApplicationContextInitializer=\
com.it.springboot.listener.HelloApplicationContextInitializer
org.springframework.boot.SpringApplicationRunListener=\
com.it.springboot.listener.HelloSpringApplicationRunListener
2.只需要放在ioc容器中
1)、ApplicationRunner
@Component
public class HelloApplicationRunner implements ApplicationRunner {
@Override
public void run(ApplicationArguments args) throws Exception {
System.out.println("HelloApplicationRunner....run");
}
}
2)、CommandLineRunner
@Component
public class HelloCommandLineRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("HelloCommandLineRunner....run");
}
}