SpringBoot启动过程
-
创建 SpringApplication
-
保存一些信息。
-
判定当前应用的类型。ClassUtils。Servlet
-
bootstrappers：初始启动引导器（List
）：去spring.factories文件中找 org.springframework.boot.Bootstrapper -
找 ApplicationContextInitializer；去spring.factories找 ApplicationContextInitializer
-
List<ApplicationContextInitializer<?>> initializers
-
找 ApplicationListener ；应用监听器。去spring.factories找 ApplicationListener
-
List<ApplicationListener<?>> listeners
-
-
运行 SpringApplication
-
1. StopWatch
-
2. 记录应用的启动时间
-
3. 创建引导上下文（Context环境）createBootstrapContext()
- 获取到所有之前的 bootstrappers 挨个执行 intitialize() 来完成对引导启动器上下文环境设置
-
4. 让当前应用进入****headless模式。java.awt.headless
-
5. 获取所有 RunListener（运行监听器）【为了方便所有Listener进行事件感知】
-
getSpringFactoriesInstances 去spring.factories找 SpringApplicationRunListener.
**遍历** **SpringApplicationRunListener 调用 starting 方法；** -
相当于通知所有感兴趣系统正在启动过程的人，项目正在 starting。
-
-
6. 保存命令行参数；ApplicationArguments
-
准备环境 prepareEnvironment（）;
- 返回或者创建基础环境信息对象。StandardServletEnvironment
- 配置环境信息对象。- 读取所有的配置源的配置属性值。
-
绑定环境信息
- 监听器调用 listener.environmentPrepared()；通知所有的监听器当前环境准备完成 -
7. 打印Banner图
-
8. 创建IOC容器（createApplicationContext（））
- 根据项目类型（Servlet）创建容器，
- 当前会创建 AnnotationConfigServletWebServerApplicationContext
-
9. 准备ApplicationContext IOC容器的基本信息 prepareContext()
-
保存环境信息
-
IOC容器的后置处理流程。
-
应用初始化器；applyInitializers；
-
遍历所有的 ApplicationContextInitializer 。调用 initialize.。来对ioc容器进行初始化扩展功能
- 遍历所有的 listener 调用 contextPrepared。EventPublishRunListenr；通知所有的监听器contextPrepared
-
所有的监听器 调用 contextLoaded。通知所有的监听器 contextLoaded；
-
-
10. 刷新IOC容器。refreshContext
- 创建容器中的所有组件（Spring注解）
-
11. 容器刷新完成后工作？afterRefresh
-
12. StopWatch会显示用了多久
- 所有监听 器 调用 listeners.started(context); 通知所有的监听器 started
-
13 调用所有runners；callRunners()
-
获取容器中的 ApplicationRunner
- 获取容器中的 CommandLineRunner
- 合并所有runner并且按照@Order进行排序
- 遍历所有的runner。调用 run 方法 -
如果以上有异常，
- 调用Listener 的 failed
-
调用所有监听器的 running 方法 listeners.running(context); 通知所有的监听器 running
-
running如果有问题。继续通知 failed 。调用所有 Listener 的 failed；通知所有的监听器 failed
常见的5个重要的类
/**
* @author WGR
* @create 2021/3/8 -- 13:25
*/
public class MyApplicationContextInitializer implements ApplicationContextInitializer {
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
System.out.println("MyApplicationContextInitializer ....initialize.... ");
}
}
/**
* @author WGR
* @create 2021/3/8 -- 13:29
*/
public class MyApplicationListener implements ApplicationListener {
@Override
public void onApplicationEvent(ApplicationEvent event) {
System.out.println("MyApplicationListener.....onApplicationEvent...");
}
}
/**
* @author WGR
* @create 2021/3/8 -- 13:32
*/
@Component
public class MyApplicationRunner implements ApplicationRunner {
@Override
public void run(ApplicationArguments args) throws Exception {
System.out.println("MyApplicationRunner....run....");
}
}
/**
* @author WGR
* @create 2021/3/8 -- 13:33
*/
@Component
public class MyCommandLineRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("MyCommandLineRunner....run....");
}
}
/**
* @author WGR
* @create 2021/3/8 -- 13:30
*/
public class MySpringApplicationRunListener implements SpringApplicationRunListener {
private final SpringApplication application;
public MySpringApplicationRunListener(SpringApplication application, String[] args) {
this.application = application;
}
@Override
public void starting(ConfigurableBootstrapContext bootstrapContext) {
System.out.println("MySpringApplicationRunListener....starting....");
}
@Override
public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext, ConfigurableEnvironment environment) {
System.out.println("MySpringApplicationRunListener....environmentPrepared....");
}
@Override
public void contextPrepared(ConfigurableApplicationContext context) {
System.out.println("MySpringApplicationRunListener....contextPrepared....");
}
@Override
public void contextLoaded(ConfigurableApplicationContext context) {
System.out.println("MySpringApplicationRunListener....contextLoaded....");
}
@Override
public void started(ConfigurableApplicationContext context) {
System.out.println("MySpringApplicationRunListener....started....");
}
@Override
public void running(ConfigurableApplicationContext context) {
System.out.println("MySpringApplicationRunListener....running....");
}
@Override
public void failed(ConfigurableApplicationContext context, Throwable exception) {
System.out.println("MySpringApplicationRunListener....failed....");
}
}
注意：如果MySpringApplicationRunListener类没有构造器的话，会报下面这个错
运行的周期如下：
MyApplicationListener.....onApplicationEvent...
MySpringApplicationRunListener....starting....
MyApplicationListener.....onApplicationEvent...
MySpringApplicationRunListener....environmentPrepared....
. ____ _ __ _ _
/\ / ___'_ __ _ _(_)_ __ __ _
( ( )\___ | '_ | '_| | '_ / _` |
\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.4.2)
MyApplicationContextInitializer ....initialize....
MyApplicationListener.....onApplicationEvent...
MySpringApplicationRunListener....contextPrepared....
2021-03-08 13:47:46.528 INFO 7736 --- [ main] com.dalianpai.admin.AdminApplication : Starting AdminApplication using Java 1.8.0_131 on WGR-PC with PID 7736 (E:IdeaSpacedemospring-boot-admin argetclasses started by asus in E:IdeaSpacedemo)
2021-03-08 13:47:46.532 INFO 7736 --- [ main] com.dalianpai.admin.AdminApplication : No active profile set, falling back to default profiles: default
MyApplicationListener.....onApplicationEvent...
MySpringApplicationRunListener....contextLoaded....
2021-03-08 13:47:48.519 INFO 7736 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8888 (http)
2021-03-08 13:47:48.528 INFO 7736 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-03-08 13:47:48.528 INFO 7736 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.41]
2021-03-08 13:47:48.622 INFO 7736 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2021-03-08 13:47:48.622 INFO 7736 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1969 ms
2021-03-08 13:47:48.871 INFO 7736 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2021-03-08 13:47:48.972 WARN 7736 --- [ main] ion$DefaultTemplateResolverConfiguration : Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)
2021-03-08 13:47:49.366 INFO 7736 --- [ main] o.s.b.a.e.web.EndpointLinksResolver : Exposing 2 endpoint(s) beneath base path '/actuator'
2021-03-08 13:47:49.403 INFO 7736 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8888 (http) with context path ''
MyApplicationListener.....onApplicationEvent...
MyApplicationListener.....onApplicationEvent...
2021-03-08 13:47:49.417 INFO 7736 --- [ main] com.dalianpai.admin.AdminApplication : Started AdminApplication in 3.504 seconds (JVM running for 6.046)
MyApplicationListener.....onApplicationEvent...
MyApplicationListener.....onApplicationEvent...
MySpringApplicationRunListener....started....
MyApplicationRunner....run....
MyCommandLineRunner....run....
MyApplicationListener.....onApplicationEvent...
MyApplicationListener.....onApplicationEvent...
MySpringApplicationRunListener....running....