先 autowired
autowired 之后再执行
package com.example.demo; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.stereotype.Component; import javax.annotation.PostConstruct; @Component class A { void print() { System.out.println("A"); } } @Component class B { @Autowired A a; @PostConstruct void init() { a.print(); } } @SpringBootApplication public class DemoApplication { @Autowired B b; public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } } 文章来源: https://blog.csdn.net/YYecust/article/details/88846203