在springboot启动后，容器刷新前加入新的bean、或者class

实现 自定义的包扫描。

public class CustomComponentScan implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, EnvironmentAware {

    private ResourceLoader resourceLoader;
    private Environment environment;
    @Override
    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }
    @Override
    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }

    @Override
    public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) {
		// 可以写死或者从 environment 中获取要加载的 jar 路径，可以是本地的可以是网络的
        URL[] urls = new URL[]{...};

        // 注入 系统classloader,这样才能扫描到，并且类加载器能找到class，不会classnotfound
        try {
            Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
            if (!method.isAccessible()) {
                method.setAccessible(true);
            }
            for (URL url : urls) {
                method.invoke(resourceLoader.getClassLoader(), url);
            }
        } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
            throw new RuntimeException(e);
        }

        // 扫描 bean定义
        int scan = new ClassPathBeanDefinitionScanner(beanDefinitionRegistry, true, environment, resourceLoader)
                .scan("这里是要扫描的包名，比如：com.demo.xxx");
    }
}

在启动类中引入

@SpringBootApplication
// 引入
@Import(CustomComponentScan.class)
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}