SpringApplication到底run了什么（下）

Java学习录

发布于 2019-09-26 14:34:50

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发布于 2019-09-26 14:34:50

在上篇文章中SpringApplication到底run了什么（上）中，我们分析了下面这个run方法的前半部分，本篇文章继续开工

public ConfigurableApplicationContext run(String... args) {
           //。。。
        //接上文继续
		configureIgnoreBeanInfo(environment);
		Banner printedBanner = printBanner(environment);
		context = createApplicationContext();
		exceptionReporters = getSpringFactoriesInstances(
				SpringBootExceptionReporter.class,
				new Class[] { ConfigurableApplicationContext.class }, context);
		prepareContext(context, environment, listeners, applicationArguments,
				printedBanner);
		refreshContext(context);
		afterRefresh(context, applicationArguments);
		stopWatch.stop();
		if (this.logStartupInfo) {
			new StartupInfoLogger(this.mainApplicationClass)
					.logStarted(getApplicationLog(), stopWatch);
		}
		listeners.started(context);
		callRunners(context, applicationArguments);
	}
	catch (Throwable ex) {
		handleRunFailure(context, listeners, exceptionReporters, ex);
		throw new IllegalStateException(ex);
	}
	listeners.running(context);
	return context;
}

获取系统属性spring.beaninfo.ignore

private void configureIgnoreBeanInfo(ConfigurableEnvironment environment) {
		if (System.getProperty(
				CachedIntrospectionResults."spring.beaninfo.ignore") == null) {
			Boolean ignore = environment.getProperty("spring.beaninfo.ignore",
					Boolean.class, Boolean.TRUE);
			System.setProperty(CachedIntrospectionResults."spring.beaninfo.ignore",
					ignore.toString());
		}
	}

但是这个属性的作用还真不知道。。

打印banner
根据当前环境创建ApplicationContext

protected ConfigurableApplicationContext createApplicationContext() {
		Class<?> contextClass = this.applicationContextClass;
		if (contextClass == null) {
			try {
				switch (this.webApplicationType) {
				case SERVLET:
					contextClass = Class.forName(DEFAULT_WEB_CONTEXT_CLASS);
					break;
				case REACTIVE:
					contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
					break;
				default:
					contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
				}
			}
			catch (ClassNotFoundException ex) {
				throw new IllegalStateException(
						"Unable create a default ApplicationContext, "
								+ "please specify an ApplicationContextClass",
						ex);
			}
		}
		return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
	}

基于咱们的Servlet环境，所以创建的ApplicationContext为AnnotationConfigServletWebServerApplicationContext

加载SpringBootExceptionReporter，这个类里包含了SpringBoot启动失败后异常处理相关的组件

private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,
			Class<?>[] parameterTypes, Object... args) {
		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
		Set<String> names = new LinkedHashSet<>(
				SpringFactoriesLoader.loadFactoryNames(type, classLoader));
		List<T> instances = createSpringFactoriesInstances(type, parameterTypes,
				classLoader, args, names);
		AnnotationAwareOrderComparator.sort(instances);
		return instances;
	}

10 prepareContext 这一块还是比较长的

private void prepareContext(ConfigurableApplicationContext context,
        ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
        ApplicationArguments applicationArguments, Banner printedBanner) {
    context.setEnvironment(environment);
    postProcessApplicationContext(context);
    applyInitializers(context);
    listeners.contextPrepared(context);
    if (this.logStartupInfo) {
        logStartupInfo(context.getParent() == null);
        logStartupProfileInfo(context);
    }

    context.getBeanFactory().registerSingleton("springApplicationArguments",
            applicationArguments);
    if (printedBanner != null) {
        context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
    }

    // Load the sources
    Set<Object> sources = getAllSources();
    Assert.notEmpty(sources, "Sources must not be empty");
    load(context, sources.toArray(new Object[0]));
    listeners.contextLoaded(context);
}

1. 第一行，将context中相关的environment全部替换


public void setEnvironment(ConfigurableEnvironment environment) {
    super.setEnvironment(environment);            // 设置context的environment
    this.reader.setEnvironment(environment);    // 实例化context的reader属性的conditionEvaluator属性
    this.scanner.setEnvironment(environment);    // 设置context的scanner属性的environment属性
}

2. 上下文后处理


protected void postProcessApplicationContext(ConfigurableApplicationContext context) {
    if (this.beanNameGenerator != null) {
        context.getBeanFactory().registerSingleton(
                AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR,
                this.beanNameGenerator);
    }
    if (this.resourceLoader != null) {
        if (context instanceof GenericApplicationContext) {
            ((GenericApplicationContext) context)
                    .setResourceLoader(this.resourceLoader);
        }
        if (context instanceof DefaultResourceLoader) {
            ((DefaultResourceLoader) context)
                    .setClassLoader(this.resourceLoader.getClassLoader());
        }
    }
}

这一块默认beanNameGenerator和resourceLoader都是空的，只有当我们自定义这两个对象时才会把容器内的bean替换 3. 执行所有的ApplicationContextInitializer的initialize方法


protected void applyInitializers(ConfigurableApplicationContext context) {
    for (ApplicationContextInitializer initializer : getInitializers()) {
        Class<?> requiredType = GenericTypeResolver.resolveTypeArgument(
                initializer.getClass(), ApplicationContextInitializer.class);
        Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");
        initializer.initialize(context);
    }
}

4. `listeners.contextPrepared(context)`这是个空方法，没有实现，一个Spring的扩展点
5. 打印profile
6. 注册bean：`springApplicationArguments`
7. 发布事件

public void contextLoaded(ConfigurableApplicationContext context) {
		for (ApplicationListener<?> listener : this.application.getListeners()) {
			if (listener instanceof ApplicationContextAware) {
				((ApplicationContextAware) listener).setApplicationContext(context);
			}
			context.addApplicationListener(listener);
		}
		this.initialMulticaster.multicastEvent(
				new ApplicationPreparedEvent(this.application, this.args, context));
	}

这里不仅发布了ApplicationPreparedEvent事件，还往实现了ApplicationContextAware接口的监听器中注入了context容器 8. load，其实就是创建了一个BeanDefinitionLoader对象

protected void load(ApplicationContext context, Object[] sources) {
		if (logger.isDebugEnabled()) {
			logger.debug(
					"Loading source " + StringUtils.arrayToCommaDelimitedString(sources));
		}
		BeanDefinitionLoader loader = createBeanDefinitionLoader(
				getBeanDefinitionRegistry(context), sources);
		if (this.beanNameGenerator != null) {
			loader.setBeanNameGenerator(this.beanNameGenerator);
		}
		if (this.resourceLoader != null) {
			loader.setResourceLoader(this.resourceLoader);
		}
		if (this.environment != null) {
			loader.setEnvironment(this.environment);
		}
		loader.load();
	}

容器的初始化refreshContext 这个方法最后还是调用的AbstractApplicationContext类的refresh方法，由于篇幅过长这里就不展开了，感兴趣的同学可以参考这篇文章：基于注解的SpringIOC源码解析

public void refresh() throws BeansException, IllegalStateException {
   synchronized (this.startupShutdownMonitor) {
      // 记录容器的启动时间、标记“已启动”状态、检查环境变量
      prepareRefresh();
      // 初始化BeanFactory容器、注册BeanDefinition
      ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
      // 设置 BeanFactory 的类加载器，添加几个 BeanPostProcessor，手动注册几个特殊的 bean
      prepareBeanFactory(beanFactory);
      try {
         // 扩展点
         postProcessBeanFactory(beanFactory);
         // 调用 BeanFactoryPostProcessor 各个实现类的 postProcessBeanFactory(factory) 方法
         invokeBeanFactoryPostProcessors(beanFactory);
         // 注册 BeanPostProcessor 的实现类
         registerBeanPostProcessors(beanFactory);
         // 初始化MessageSource
         initMessageSource();
         // 初始化事件广播器
         initApplicationEventMulticaster();
         // 扩展点
         onRefresh();
         // 注册事件监听器
         registerListeners();
         // 初始化所有的 singleton beans
         finishBeanFactoryInitialization(beanFactory);
         // 广播事件
         finishRefresh();
      }
      catch (BeansException ex) {
         if (logger.isWarnEnabled()) {
            logger.warn("Exception encountered during context initialization - " +
                  "cancelling refresh attempt: " + ex);
         }
         // 销毁已经初始化的的Bean
         destroyBeans();
         // 设置 'active' 状态
         cancelRefresh(ex);
         throw ex;
      }
      finally {
         // 清除缓存
         resetCommonCaches();
      }
   }
}

afterRefresh 这里没有任何实现，Spring留给我们的扩展点
停止之前启动的计时装置，然后发送ApplicationStartedEvent事件
调用系统中ApplicationRunner以及CommandLineRunner接口的实现类，关于这两个接口的使用可以参考我的这篇文章：Java项目启动时执行指定方法的几种方式

private void callRunners(ApplicationContext context, ApplicationArguments args) {
		List<Object> runners = new ArrayList<>();
		runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
		runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
		AnnotationAwareOrderComparator.sort(runners);
		for (Object runner : new LinkedHashSet<>(runners)) {
			if (runner instanceof ApplicationRunner) {
				callRunner((ApplicationRunner) runner, args);
			}
			if (runner instanceof CommandLineRunner) {
				callRunner((CommandLineRunner) runner, args);
			}
		}
	}