SpringBoot扩展点

1. ApplicationContextInitializer

1.1. ConfigurationWarningsApplicationContextInitializer

    @Override
    public void initialize(ConfigurableApplicationContext context) {  
        context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor(getChecks()));
    }

1.2. ContextIdApplicationContextInitializer

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        ContextId contextId = getContextId(applicationContext);
        applicationContext.setId(contextId.getId());
        applicationContext.getBeanFactory().registerSingleton(ContextId.class.getName(), contextId);
    }

1.3. DelegatingApplicationContextInitializer

    @Override
    public void initialize(ConfigurableApplicationContext context) {
        ConfigurableEnvironment environment = context.getEnvironment();
        List<Class<?>> initializerClasses = getInitializerClasses(environment);
        if (!initializerClasses.isEmpty()) {
            applyInitializerClasses(context, initializerClasses);
        }
    }

1.4. RSocketPortInfoApplicationContextInitializer

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        applicationContext.addApplicationListener(new Listener(applicationContext));
    }

1.5. ServerPortInfoApplicationContextInitializer

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        applicationContext.addApplicationListener(this);
    }

1.6. SharedMetadataReaderFactoryContextInitializer

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        applicationContext.addBeanFactoryPostProcessor(new CachingMetadataReaderFactoryPostProcessor());
    }

1.7. ConditionEvaluationReportLoggingListener

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        this.applicationContext = applicationContext;
        applicationContext.addApplicationListener(new ConditionEvaluationReportListener());
        if (applicationContext instanceof GenericApplicationContext) {
            // Get the report early in case the context fails to load
            this.report = ConditionEvaluationReport.get(this.applicationContext.getBeanFactory());
        }
    }

2. ApplicationListener

2.1. ClearCachesApplicationListener

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        ReflectionUtils.clearCache();
        clearClassLoaderCaches(Thread.currentThread().getContextClassLoader());
    }

2.2. ParentContextCloserApplicationListener

    @Override
    public void onApplicationEvent(ParentContextAvailableEvent event) {
        maybeInstallListenerInParent(event.getApplicationContext());
    }

2.3. CloudFoundryVcapEnvironmentPostProcessor

    @Override
    public void onApplicationEvent(ApplicationPreparedEvent event) {
        logger.switchTo(CloudFoundryVcapEnvironmentPostProcessor.class);
    }

2.4. FileEncodingApplicationListener

2.5. AnsiOutputApplicationListener

    @Override
    public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
        ConfigurableEnvironment environment = event.getEnvironment();
        String desired = environment.getProperty("spring.mandatory-file-encoding");
        if (desired == null) {
            return;
        }
        String encoding = System.getProperty("file.encoding");
        if (encoding != null && !desired.equalsIgnoreCase(encoding)) {
            if (logger.isErrorEnabled()) {
                logger.error("System property 'file.encoding' is currently '" + encoding + "'. It should be '" + desired
                        + "' (as defined in 'spring.mandatoryFileEncoding').");
                logger.error("Environment variable LANG is '" + System.getenv("LANG")
                        + "'. You could use a locale setting that matches encoding='" + desired + "'.");
                logger.error("Environment variable LC_ALL is '" + System.getenv("LC_ALL")
                        + "'. You could use a locale setting that matches encoding='" + desired + "'.");
            }
            throw new IllegalStateException("The Java Virtual Machine has not been configured to use the "
                    + "desired default character encoding (" + desired + ").");
        }
    }

2.6. ConfigFileApplicationListener

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationEnvironmentPreparedEvent) {
            onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
        }
        if (event instanceof ApplicationPreparedEvent) {
            onApplicationPreparedEvent(event);
        }
    }
    private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
        List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();
        postProcessors.add(this);
        AnnotationAwareOrderComparator.sort(postProcessors);
        for (EnvironmentPostProcessor postProcessor : postProcessors) {
            postProcessor.postProcessEnvironment(event.getEnvironment(), event.getSpringApplication());
        }
    }
    List<EnvironmentPostProcessor> loadPostProcessors() {
        //加载了并实例化了
        //org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor
        //org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor
        //org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor
        //org.springframework.boot.reactor.DebugAgentEnvironmentPostProcessor        
        return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class, getClass().getClassLoader());
    }

2.7. DelegatingApplicationListener

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationEnvironmentPreparedEvent) {
            List<ApplicationListener<ApplicationEvent>> delegates = getListeners(
                    ((ApplicationEnvironmentPreparedEvent) event).getEnvironment());
            if (delegates.isEmpty()) {
                return;
            }
            this.multicaster = new SimpleApplicationEventMulticaster();
            for (ApplicationListener<ApplicationEvent> listener : delegates) {
                this.multicaster.addApplicationListener(listener);
            }
        }
        if (this.multicaster != null) {
            this.multicaster.multicastEvent(event);
        }
    }

2.8. ClasspathLoggingApplicationListener

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (logger.isDebugEnabled()) {
            if (event instanceof ApplicationEnvironmentPreparedEvent) {
                logger.debug("Application started with classpath: " + getClasspath());
            }
            else if (event instanceof ApplicationFailedEvent) {
                logger.debug("Application failed to start with classpath: " + getClasspath());
            }
        }
    }

2.9. LoggingApplicationListener

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationStartingEvent) {
            onApplicationStartingEvent((ApplicationStartingEvent) event);
        }
        else if (event instanceof ApplicationEnvironmentPreparedEvent) {
            onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
        }
        else if (event instanceof ApplicationPreparedEvent) {
            onApplicationPreparedEvent((ApplicationPreparedEvent) event);
        }
        else if (event instanceof ContextClosedEvent
                && ((ContextClosedEvent) event).getApplicationContext().getParent() == null) {
            onContextClosedEvent();
        }
        else if (event instanceof ApplicationFailedEvent) {
            onApplicationFailedEvent();
        }
    }

2.10. LiquibaseServiceLocatorApplicationListener

    @Override
    public void onApplicationEvent(ApplicationStartingEvent event) {
        if (ClassUtils.isPresent("liquibase.servicelocator.CustomResolverServiceLocator",
                event.getSpringApplication().getClassLoader())) {
            new LiquibasePresent().replaceServiceLocator();
        }
    }

2.11. BackgroundPreinitializer

    @Override
    public void onApplicationEvent(SpringApplicationEvent event) {
        if (!Boolean.getBoolean(IGNORE_BACKGROUNDPREINITIALIZER_PROPERTY_NAME)
                && event instanceof ApplicationEnvironmentPreparedEvent && multipleProcessors()
                && preinitializationStarted.compareAndSet(false, true)) {
            performPreinitialization();
        }
        if ((event instanceof ApplicationReadyEvent || event instanceof ApplicationFailedEvent)
                && preinitializationStarted.get()) {
            try {
                preinitializationComplete.await();
            }
            catch (InterruptedException ex) {
                Thread.currentThread().interrupt();
            }
        }
    }

2.12. Initializer增加的

2.12.1 ServerPortInfoApplicationContextInitializer

    @Override
    public void onApplicationEvent(WebServerInitializedEvent event) {
        String propertyName = "local." + getName(event.getApplicationContext()) + ".port";
        setPortProperty(event.getApplicationContext(), propertyName, event.getWebServer().getPort());
    }

3. BeanDefinitionRegistryPostProcessor

MapperScannerConfigurer.postProcessBeanDefinitionRegistry方法，用来扫描指定路径下的接口，注册为beanClass为MapperFactoryBean的BeanDefinition

4. ImportBeanDefinitionRegistrar

MapperScannerRegistrar，用来处理@MapperScan的basePackage

5. BeanFactoryPostProcessor

6. ImportSelector

7. BeanPostProcessor

8. FactoryBean