IOC 容器启动入口

建立测试环境

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public class SpringSourceTest {
    public static void main(String[] args) {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("application.xml");

        MyService myService = context.getBean(MyService.class);
        myService.sayHello();
    }
}

application.xml:

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<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="myService" class="com.example.MyService"/>
</beans>

MyService.java:

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public class MyService {
    public void sayHello() {
        System.out.println("Hello Spring Source!");
    }
}

第一个关键类：ClassPathXmlApplicationContext

入口：

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ApplicationContext context =
    new ClassPathXmlApplicationContext("application.xml");

构造方法里会调用：

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this.refresh();

跟源码看 refresh()

refresh() 定义在 AbstractApplicationContext

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@Override
public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // 1. 准备工作
        prepareRefresh();

        // 2. 获取 BeanFactory
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

        // 3. BeanFactory 的准备工作
        prepareBeanFactory(beanFactory);

        // 4. BeanFactory 的后置处理
        postProcessBeanFactory(beanFactory);

        // 5. 执行 BeanFactoryPostProcessor
        invokeBeanFactoryPostProcessors(beanFactory);

        // 6. 注册 BeanPostProcessor
        registerBeanPostProcessors(beanFactory);

        // 7. 初始化消息源
        initMessageSource();

        // 8. 初始化事件广播器
        initApplicationEventMulticaster();

        // 9. 子类扩展点
        onRefresh();

        // 10. 注册监听器
        registerListeners();

        // 11. 实例化所有非懒加载的单例 Bean
        finishBeanFactoryInitialization(beanFactory);

        // 12. 完成刷新，发布事件
        finishRefresh();
    }
}