Spring与SpringBoot对Environment的初始化过程事件发布对比

青旅半醒 2024-04-17 05:22 32阅读 0赞

### 概述： ###

Spring在初始化environment过程中没有发布有关environment的事件，而SpringBoot会在准备好environment的时候就发布一个applicationEnvPreparedEnvent。但Spring可以发布ContextRefreshedEvent、ContextStartedEvent、ContextStoppedEvent、ContextClosedEvent。

### 文章目录 ###

*   *   *  概述：
         *   *  Spring
             *  SpringBoot

#### Spring ####

HttpServletBean.init：创建environment

public final void init() throws ServletException {
    
       // Set bean properties from init parameters.
       PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
       if (!pvs.isEmpty()) {
          try {
             BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
             ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
             //1.创建environment，注册ResourceEditor
              bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
             initBeanWrapper(bw);
             bw.setPropertyValues(pvs, true);
          }
          catch (BeansException ex) {
             if (logger.isErrorEnabled()) {
                logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
             }
             throw ex;
          }
       }
    
       // Let subclasses do whatever initialization they like.
       initServletBean();
    }

1.创建environment

public ConfigurableEnvironment getEnvironment() {
    		if (this.environment == null) {
                //返回一个StandardServletEnvironment
    			this.environment = createEnvironment();
    		}
    		return this.environment;
    	}
    
    	protected ConfigurableEnvironment createEnvironment() {
    		return new StandardServletEnvironment();
    	}

FrameworkServlet.configureAndRefreshWebApplicationContext：可以配置environment

protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
    		if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
    			// The application context id is still set to its original default value
    			// -> assign a more useful id based on available information
    			if (this.contextId != null) {
    				wac.setId(this.contextId);
    			}
    			else {
    				// Generate default id...
    				wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
    						ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
    			}
    		}
    
    		wac.setServletContext(getServletContext());
    		wac.setServletConfig(getServletConfig());
    		wac.setNamespace(getNamespace());
    		wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));
    
    		ConfigurableEnvironment env = wac.getEnvironment();
    		if (env instanceof ConfigurableWebEnvironment) {
                //配置environment
    			((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
    		}
    
    		postProcessWebApplicationContext(wac);
    		applyInitializers(wac);
    		wac.refresh();
    	}

#### SpringBoot ####

创建好了SpringApplication—>创建environment，context

public ConfigurableApplicationContext run(String... args) {
       StopWatch stopWatch = new StopWatch();
       stopWatch.start();
       ConfigurableApplicationContext context = null;
       Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
       configureHeadlessProperty();
        //初始化SpringApplicationRunListener
       SpringApplicationRunListeners listeners = getRunListeners(args);
        //发布ApplicationStartedEvent
       listeners.starting();
       try {
          ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                args);
           //1.准备environment,发布ApplicationEnvironmentPreparedEvent
          ConfigurableEnvironment environment = prepareEnvironment(listeners,
                applicationArguments);
          configureIgnoreBeanInfo(environment);
           //打印Banner
          Banner printedBanner = printBanner(environment);
           //创建ApplicationContext
          context = createApplicationContext();
          exceptionReporters = getSpringFactoriesInstances(
                SpringBootExceptionReporter.class,
                new Class[] { ConfigurableApplicationContext.class }, context);
           //装配ApplicationContext
          prepareContext(context, environment, listeners, applicationArguments,
                printedBanner);
           //refresh（）
          refreshContext(context);
          afterRefresh(context, applicationArguments);
          stopWatch.stop();
          if (this.logStartupInfo) {
             new StartupInfoLogger(this.mainApplicationClass)
                   .logStarted(getApplicationLog(), stopWatch);
          }
           //发布ApplicationStartedEvent
          listeners.started(context);
          callRunners(context, applicationArguments);
       }
       catch (Throwable ex) {
          handleRunFailure(context, ex, exceptionReporters, listeners);
          throw new IllegalStateException(ex);
       }
    
       try {
          listeners.running(context);
       }
       catch (Throwable ex) {
          handleRunFailure(context, ex, exceptionReporters, null);
          throw new IllegalStateException(ex);
       }
       return context;
    }

1.准备environment,发布ApplicationEnvironmentPreparedEvent

private ConfigurableEnvironment prepareEnvironment(
          SpringApplicationRunListeners listeners,
          ApplicationArguments applicationArguments) {
       // 1.1获取environment
       ConfigurableEnvironment environment = getOrCreateEnvironment();
        //1.2为environment配置ConversionService，properties，profiles
       configureEnvironment(environment, applicationArguments.getSourceArgs());
        //1.3发布ApplicationEnvironmentPreparedEvent
       listeners.environmentPrepared(environment);
       bindToSpringApplication(environment);
       if (!this.isCustomEnvironment) {
          environment = new EnvironmentConverter(getClassLoader())
                .convertEnvironmentIfNecessary(environment, deduceEnvironmentClass());
       }
       ConfigurationPropertySources.attach(environment);
       return environment;
    }

1.1获取environment

private ConfigurableEnvironment getOrCreateEnvironment() {
       if (this.environment != null) {
          return this.environment;
       }
       switch (this.webApplicationType) {
       case SERVLET:
               //返回一个StandardServletEnvironment
          return new StandardServletEnvironment();
       case REACTIVE:
          return new StandardReactiveWebEnvironment();
       default:
          return new StandardEnvironment();
       }
    }