SpringBoot学习笔记(三) 自动装配原理

最新推荐文章于 2024-12-02 23:52:23 发布

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最新推荐文章于 2024-12-02 23:52:23 发布 · 489 阅读

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本文分析SpringBoot自动装配原理，它源于Spring，省去简单模式下xml配置文件的繁琐。通过源码解读，介绍从run方法进入，逐步深入到各个关键方法，分析如何从spring.factories中加载XXXAutoConfigration，以及将其注册为Bean的过程，最后完成自动装配。

继SpringBoot学习笔记(二) 整合redis+mybatis+Dubbo，本篇文章我们开始分析SpringBoot的自动装配原理。

概述

前面已经介绍了Spring的加载过程，经历扫描配置文件--收集beanName--实例化bean这几步，SpringBoot同样如此，源于Spring，高于Spring，省去了”简单模式(特殊场景如多数据源引入,需要额外的单独配置)下xml配置文件的繁琐过程。下面让我们来揭秘SpringBoot的自动装配原理。

源码解读

1.先从run方法进入，

public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

2.进入到run方法中

public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {
        return run(new Class[]{primarySource}, args);
    }

3.最后点到这里

4.继续深入

private void refreshContext(ConfigurableApplicationContext context) {
        this.refresh((ApplicationContext)context);
        if (this.registerShutdownHook) {
            try {
                context.registerShutdownHook();
            } catch (AccessControlException var3) {
                ;
            }
        }

    }

5.进入到refresh

protected void refresh(ConfigurableApplicationContext applicationContext) {
        applicationContext.refresh();
    }

6.继续进入方法

org.springframework.context.support.AbstractApplicationContext#refresh

public void refresh() throws BeansException, IllegalStateException {
        Object var1 = this.startupShutdownMonitor;
        synchronized(this.startupShutdownMonitor) {
            this.prepareRefresh();
            ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
            this.prepareBeanFactory(beanFactory);

            try {
                this.postProcessBeanFactory(beanFactory);
                this.invokeBeanFactoryPostProcessors(beanFactory);  //看这里
                this.registerBeanPostProcessors(beanFactory);
                this.initMessageSource();
                this.initApplicationEventMulticaster();
                this.onRefresh();
                this.registerListeners();
                this.finishBeanFactoryInitialization(beanFactory);
                this.finishRefresh();
            } catch (BeansException var9) {
                if (this.logger.isWarnEnabled()) {
                    this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9);
                }

                this.destroyBeans();
                this.cancelRefresh(var9);
                throw var9;
            } finally {
                this.resetCommonCaches();
            }

        }
    }

7.进入到invokeBeanFactoryPostProcessors方法内部

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        //这里
       PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, this.getBeanFactoryPostProcessors());
        if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean("loadTimeWeaver")) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }
    }

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

     sortPostProcessors(currentRegistryProcessors, beanFactory);

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