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SpringApplication到底run了什么(下)

04-18 15:54 418浏览
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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;    
}

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);            
    }        
    }    
}
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