spring启动.png

1.加载启动class类

AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(MainConfig.class);

2.三步

public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
    // 父类构造方法创建DefaultListableBeanFactory
    // 一步：创建AnnotatedBeanDefinitionReader与ClassPathBeanDefinitionScanner
    this();
    // 二步：注册componentClasses
    this.register(componentClasses);
    // 三步：上下文刷新
    this.refresh();
}

3.this方法

public AnnotationConfigApplicationContext() {
    StartupStep createAnnotatedBeanDefReader = this.getApplicationStartup().start("spring.context.annotated-bean-reader.create");
    // 注解BeanDefinition读取器：用来读取被注解的bean
    // 1.赋值beanNameGenerator：beanName生成器
    // 2.赋值scopeMetadataResolver：解释scope注解值
    // 3.赋值BeanDefinitionRegistry：注册bean定义
    // 4.赋值conditionEvaluator，用于@Conditional注解
    // 5.赋值AnnotationAwareOrderComparator（解析order注解）/ContextAnnotationAutowireCandidateResolver（解析lazy注解）
    // 6.设置BeanDefinitionHolder，设置六个处理器，用于解析class文件
    // -->org.springframework.context.annotation.internalConfigurationAnnotationProcessor  Configuration annotation processor
    // -->org.springframework.context.annotation.internalAutowiredAnnotationProcessor  Autowired annotation processor
    // -->org.springframework.context.annotation.internalCommonAnnotationProcessor  管理managed JSR-250 注解处理器
    // -->org.springframework.context.annotation.internalPersistenceAnnotationProcessor  JPA
    // -->org.springframework.context.event.internalEventListenerProcessor  @EventListener
    // -->org.springframework.context.event.internalEventListenerFactory 管理EventListenerFactory
    this.reader = new AnnotatedBeanDefinitionReader(this);
    createAnnotatedBeanDefReader.end();
    // ClassPath BeanDefinition扫描器:指定路径下的所有class逐一排查，符合的class封装成BeanDefinition
    // 1.注册默认的注解过滤器，支持Component/JSR-250 ManagedBean/JSR-330 Named
    // 2.赋值resourcePatternResolver，格式解析
    // 3.赋值metadataReaderFactory,
    this.scanner = new ClassPathBeanDefinitionScanner(this);
}

4.register(componentClasses)

public void register(Class<?>... componentClasses) {
    for (Class<?> componentClass : componentClasses) {
        registerBean(componentClass);
    }
}

public void registerBean(Class<?> beanClass) {
    doRegisterBean(beanClass, null, null, null, null);
}

private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name,
            @Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier,
            @Nullable BeanDefinitionCustomizer[] customizers) {
    // 启动类变成注解BeanDefinition，里面会把启动类的注解信息封装起来。
    AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass);
    // condition注解
    if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
        return;
    }
    // 支持jdk1.8 supplier
    abd.setInstanceSupplier(supplier);
    // 解释scope注解
    ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
    abd.setScope(scopeMetadata.getScopeName());
    // 生成beanName FooBah会变成fooBah X会变成x，但是URL会变成URL
    String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
    // 解析lazy注解，放入beanDefinition
    AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
    if (qualifiers != null) {
        for (Class<? extends Annotation> qualifier : qualifiers) {
            if (Primary.class == qualifier) {
                abd.setPrimary(true);
            }
            else if (Lazy.class == qualifier) {
                abd.setLazyInit(true);
            }
            else {
                abd.addQualifier(new AutowireCandidateQualifier(qualifier));
            }
        }
    }
    if (customizers != null) {
        for (BeanDefinitionCustomizer customizer : customizers) {
            customizer.customize(abd);
        }
    }

    BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
    // 检查是否需要使用动态代理，使用了动态代理则返回代理BeanDefinition,里面封装了被增强的对象
    definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
    // 放入容器的beanDefinitionMap<beanName, beanDefinition>与beanDefinitionNames<beanName>中
    // 别名与beanName绑定
    BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
}

5.refresh();

public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
            // Prepare this context for refreshing.
            // 1.closed设置为false，active设置为true
            // 2.模板方法initPropertySources，初始化配置，这里啥也没干
            // 3.校验一些必须的参数
            // 4.初始化早期的事件监听器和事件
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            // 提供beanFactory，用于注册bean
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            // 给beanFactory设置classloader，spel表达式解析器
            // 类型转换器
            // 添加ApplicationContextAwareProcessor，处理XXXAware
            // 忽略XXXAware自动注入
            // 添加一些基础的注册依赖对象
            // 添加ApplicationListenerDetector，后置处理器，发现监听器(ApplicationListener)
            // 利用beanFactory提前注册一些单例bean：environment/systemProperties/systemEnvironment
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                // 模板方法，留给子类使用
                postProcessBeanFactory(beanFactory);

                StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
                // Invoke factory processors registered as beans in the context.
                // 添加BeanDefinitionRegistryPostProcessor ConfigurationAnnotationProcessor，执行postProcessBeanDefinitionRegistry方法
                // 执行通过ConfigurationAnnotationProcessor加载进来的BeanFactoryPostProcessors
                // 解析@Configuration class，里面会扫面所有含有Component/PropertySources/PropertySource/ComponentScans/ComponentScan
                // /Import/ImportResourceBean/注解的类（收集材料）
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                // 解析BeanPostProcessor，前面放置的AutowiredAnnotationProcessor/CommonAnnotationProcessor与
                // ApplicationContextAwareProcessor/ApplicationListenerDetector/ImportAwareBeanPostProcessor
                registerBeanPostProcessors(beanFactory);
                beanPostProcess.end();

                // Initialize message source for this context.
                // 初始化国际化资源
                initMessageSource();

                // Initialize event multicaster for this context.
                // 初始化事件播放器
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                // 模板方法
                onRefresh();

                // Check for listener beans and register them.
                // 注册监听器（把监听器绑定到多播器上面）
                // 发布一些早期的事件
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                // 初始化非懒加载的bean
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset 'active' flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // Reset common introspection caches in Spring's core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
                contextRefresh.end();
            }
    }
}