1.springboot启动流程

SpringBoot版本：2.1.2.RELEASE

1.maven

 <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.2.RELEASE</version>
 </parent>

 　 <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

2.主程序入口,两种方式

• 　　SpringApplication.run(Application.class);
• 　　new SpringApplication(Application.class).run(args);可以通过设置springApplication的defaultProperties等属性，设置一些配置参数信息

  2.1. 初始化springApplication对象

　　　　

　　　　listeners.starting();  　　EventPublishingRunListener

　　　　发布一个ApplicationStartingEvent事件

• • 　LoggingApplicationListener
  • 　BackgroundPreinitializer
  •    DelegatingApplicationListener
  •    LiquibaseServiceLocatorApplicationListener

  2.2. 准备环境变量 Environment

　　2.2.1.org.springframework.boot.SpringApplication#prepareEnvironment

　　　　　　 org.springframework.boot.SpringApplication#getOrCreateEnvironment　　　　　　　　　

new StandardServletEnvironment() ->new StandardEnvironment() ->new AbstractEnvironment()

public AbstractEnvironment() {
        this.propertyResolver = new PropertySourcesPropertyResolver(this.propertySources);
        this.customizePropertySources(this.propertySources);
    }

#StandardServletEnvironment
 protected void customizePropertySources(MutablePropertySources propertySources) {
        propertySources.addLast(new StubPropertySource("servletConfigInitParams"));
        propertySources.addLast(new StubPropertySource("servletContextInitParams"));
        if (JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()) {
            propertySources.addLast(new JndiPropertySource("jndiProperties"));
        }

        super.customizePropertySources(propertySources);
    }

#StandardEnvironment
protected void customizePropertySources(MutablePropertySources propertySources) {
        propertySources.addLast(new MapPropertySource("systemProperties", this.getSystemProperties()));
        propertySources.addLast(new SystemEnvironmentPropertySource("systemEnvironment", this.getSystemEnvironment()));
    }

 此时，environment中的propertySources包含servletConfigInitParams，servletContextInitParams，jndiProperties（存在的话,spring.properties中配置spring.jndi.ignore=true，且...待定），systemProperties，systemEnvironment

　　　　　　org.springframework.boot.SpringApplication#configureEnvironment

 protected void configurePropertySources(ConfigurableEnvironment environment, String[] args) {
        MutablePropertySources sources = environment.getPropertySources();
        if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {
            sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties));
        }

        if (this.addCommandLineProperties && args.length > 0) {
            String name = "commandLineArgs";
            if (sources.contains(name)) {
                PropertySource<?> source = sources.get(name);
                CompositePropertySource composite = new CompositePropertySource(name);
                composite.addPropertySource(new SimpleCommandLinePropertySource("springApplicationCommandLineArgs", args));
                composite.addPropertySource(source);
                sources.replace(name, composite);
            } else {
                sources.addFirst(new SimpleCommandLinePropertySource(args));
            }
        }

    }

　　　　　　org.springframework.boot.SpringApplicationRunListeners#environmentPrepared

　　　　　　发布一个ApplicationEnvironmentPreparedEvent

　　　

1. ConfigServerBootstrapApplicationListener

   private PropertySource<?> propertySource = new MapPropertySource("configServerClient", Collections.singletonMap("spring.cloud.config.enabled", "false"));
   
   public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
           ConfigurableEnvironment environment = event.getEnvironment();
           if (!environment.resolvePlaceholders("${spring.cloud.config.enabled:false}").equalsIgnoreCase("true") && !environment.getPropertySources().contains(this.propertySource.getName())) {
               environment.getPropertySources().addLast(this.propertySource);
           }
   
       }
   

2.  BootstrapApplicationListener
3.  LoggingSystemShutdownListener
4.  ConfigFileApplicationListener
5.  AnsiOutputApplicationListener
6.  LoggingApplicationListener
7.  BackgroundPreinitializer
8.  ClasspathLoggingApplicationListener
9.  DelegatingApplicationListener
10.  FileEncodingApplicationListener

　　

  2.3. 初始化ApplicatonContext

　　　　　org.springframework.boot.SpringApplication#createApplicationContext

　　　　　创建一个AnnotationConfigApplicationContext

　　　　　org.springframework.boot.SpringApplication#prepareContext

　　　　　发布一个ApplicationContextInitializedEvent

　　　　　org.springframework.boot.SpringApplication#refreshContext

　　　　    发布一个ContextRefreshedContext，初始化所有的Bean