Spring启动过程分析

发表于 | 更新于 | 分类于 ，

AbstractApplicationContext#refresh

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        prepareRefresh();
    
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
        prepareBeanFactory(beanFactory);
        
        try {
            postProcessBeanFactory(beanFactory);
            invokeBeanFactoryPostProcessors(beanFactory);
            registerBeanPostProcessors(beanFactory);
            initMessageSource();
            initApplicationEventMulticaster();
            onRefresh();
            registerListeners();
            finishBeanFactoryInitialization(beanFactory);
            finishRefresh();
        }
        catch (BeansException ex) {
            destroyBeans();
            cancelRefresh(ex);
            throw ex;
        }
    }
}

1. prepareRefresh()

  • 设置启动时间startupDate为当前毫秒值
  • 启动标志active为true
  • 执行子类重载方法:AbstractRefreshableWebApplicationContext#initPropertySources, 将当前应用的servletContext和servletConfig添加到属性源
  • 执行 AbstractEnvironment#validateRequiredProperties, 确保必要属性非空

2. obtainFreshBeanFactory()

主要作用: 创建BeanFactory, 加载BeanDefinition.
内部主要调用AbstractRefreshableApplicationContext#refreshBeanFactory, 定义如下

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
protected final void refreshBeanFactory() throws BeansException {
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    try {
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        beanFactory.setSerializationId(getId());
        customizeBeanFactory(beanFactory);
        loadBeanDefinitions(beanFactory);
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

createBeanFactory()通过new DefaultListableBeanFactory创建了Bean工厂, 也就是Spring默认的工厂类是DefaultListableBeanFactory
customizeBeanFactory实际是调用的子类重载的方法AbstractRefreshableApplicationContext#customizeBeanFactory, 该方法内是配置Bean工厂的allowBeanDefinitionOverriding和allowCircularReferences属性
loadBeanDefinitions()方法用来加载BeanDefinition, 实际调用的是子类重载的方法AbstractXmlApplicationContext#loadBeanDefinitions(DefaultListableBeanFactory)

3. prepareBeanFactory(beanFactory)

主要作用: 配置Bean工厂, 将内部的一些类ignore或注册为可依赖的, 主要调用ConfigurableListableBeanFactory#ignoreDependencyInterface 和 ConfigurableListableBeanFactory#registerResolvableDependency.

4. postProcessBeanFactory(beanFactory)

实际调用子类重载方法AbstractRefreshableWebApplicationContext#postProcessBeanFactory. 该方法主要:

  • 向Bean工厂添加ServletContextAwareProcessorBean后置处理器
  • 配置Bean工厂, 忽略ServletConfigAware和ServletContextAware接口依赖

5. invokeBeanFactoryPostProcessors(beanFactory)

调用所有的BeanFactoryPostProcessor, myBatis的MapperScannerConfigurer就是在此刻向Bean工厂注入了Mapper接口的BeanDefinition, 这个BeanDefinition都是工厂类, 最终调用MapperFactoryBean生成实现类.

6. registerBeanPostProcessors(beanFactory)

将Bean工厂里的BeanPostProcessor类型的Bean先实例化, 然后通过ConfigurableBeanFactory#addBeanPostProcessor将这些Bean存到beanPostProcessors属性里

7. initMessageSource()

初始化MessageSource, 该类主要是为系统提供国际化支持, 可以输出不同语言的提示信息

8. initApplicationEventMulticaster()

初始化Spring事件多播器, 默认创建一个SimpleApplicationEventMulticaster实例

9. onRefresh()

给AbstractApplicationContext的子类一个参与refresh的机会, 其中AbstractRefreshableWebApplicationContext#onRefresh初始化了主题资源

10. registerListeners()

将保存在容器中的事件监听器ApplicationListener对象注册到Spring事件多播器中

11. finishBeanFactoryInitialization(beanFactory)

实例化容器中剩余的单例Bean

12. finishRefresh()

初始化生命周期处理器, 默认实例化DefaultLifecycleProcessor, 并发布容器刷新时间ContextRefreshedEvent

13. destroyBeans()

清空容器中保存bean的相关属性

14. cancelRefresh(ex)

设置启动标志为false