ApplicationContextInitializer是在springboot启动过程(refresh方法前)调用,主要是在ApplicationContextInitializer中initialize方法中拉起了ConfigurationClassPostProcessor这个类(我在springboot启动流程中有描述)，通过这个processor实现了beandefinition。

ApplicationContextInitializer实现的3种方式：

首先创建一个实现ApplicationContextInitializer的类：

public class MyApplicationContextInitializer implements ApplicationContextInitializer {
    @Override
    public void initialize(ConfigurableApplicationContext configurableApplicationContext) {
        System.out.println("My ApplicationContextInitializer ...");
    }
}

1. 使用spring.factories

1. 在resources目录下创建META-INF文件夹

2. 创建spring.factories

   org.springframework.context.ApplicationContextInitializer=\
   com.mxiaoy.springbootstarterdemo.initializer.MyApplicationContextInitializer

   2. application.properties添加配置

3. 直接application.properties

   context.initializer.classes = com.mxiaoy.springbootstarterdemo.initializer.MyApplicationContextInitializer

   3. 直接通过add方法

    public static void main(String[] args) {
   //        SpringApplication.run(SpringBootStarterDemoApplication.class, args);
        SpringApplication springApplication = new SpringApplication(SpringBootStarterDemoApplication.class);
        // 添加实现了ApplicationContextInitializer的自定义类
        springApplication.addInitializers(new MyApplicationContextInitializer());
        springApplication.run(args);
    }