SpringBoot 创建容器

spring 容器的创建对应 SpringApplication 中 run 中调用的 createApplicationContext 方法。这里创建了一个 web 容器，接下就进去 prepareContext 容器准备阶段：

    private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
            SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
        //为容器设置环境
        context.setEnvironment(environment);
        //这里的空实现留给开发者扩展，设置数据转换的ConversionService
        postProcessApplicationContext(context);
        //执行容器中的 Initializers 的 initialize 方法
        applyInitializers(context);
        listeners.contextPrepared(context);
        if (this.logStartupInfo) {
            logStartupInfo(context.getParent() == null);
            logStartupProfileInfo(context);
        }
        // Add boot specific singleton beans
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
        if (printedBanner != null) {
            beanFactory.registerSingleton("springBootBanner", printedBanner);
        }
        if (beanFactory instanceof DefaultListableBeanFactory) {
            ((DefaultListableBeanFactory) beanFactory)
                    .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
        }
        if (this.lazyInitialization) {
            context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
        }
        // 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);
    }

看一下这里的 load 方法,这里主要把我们的启动类作为 Bean 注册到了 Spring 的容器中。

    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();
    }

    /**
     * Load the sources into the reader.
     * @return the number of loaded beans
     */
    int load() {
        int count = 0;
        for (Object source : this.sources) {
            count += load(source);
        }
        return count;
    }

    private int load(Object source) {
        Assert.notNull(source, "Source must not be null");
        if (source instanceof Class<?>) {
            return load((Class<?>) source);
        }
        if (source instanceof Resource) {
            return load((Resource) source);
        }
        if (source instanceof Package) {
            return load((Package) source);
        }
        if (source instanceof CharSequence) {
            return load((CharSequence) source);
        }
        throw new IllegalArgumentException("Invalid source type " + source.getClass());
    }

    private int load(Class<?> source) {
        if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
            // Any GroovyLoaders added in beans{} DSL can contribute beans here
            GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
            load(loader);
        }
        if (isEligible(source)) {
            this.annotatedReader.register(source);
            return 1;
        }
        return 0;
    }

再来看下 contextLoaded 方法，这里将上下文设置到监听器中，同时也把监听器添加到上下文中。最后发布了一个 ApplicationPreparedEvent 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));
    }