SpringBoot选择自有bean优先加载实现方法

 class DemoApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
  @Override
  public void initialize(ConfigurableApplicationContext applicationContext) {
      applicationContext.addBeanFactoryPostProcessor(new DemoBeanDefinitionRegistryPostProcessor());
  }
}

public class DemoBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
  // from BeanDefinitionRegistryPostProcessor interface
  @Override
  public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
// 重点在这里，这里可以把自己的 想要提起 实现的 或者初始化的 bean  加到这里
beanDefinitionRegistry.registerBeanDefinition("DemoService",new RootBeanDefinition(DemoService.class));
  }
  // from BeanDefinitionRegistryPostProcessor interface
  @Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
  }
// from PriorityOrdered  interface
  @Override
  public int getOrder() {
  // 排在 ConfigurationClassPostProcessor 之前即可
      return Ordered.LOWEST_PRECEDENCE - 1;
  }
}

public class TestService {
    // 存放系统配置
    private static Map<String, String> GLOBAL_CONF = new HashMap<>();
    @PostConstruct
    public void init() {
        // 先做初始化 GLOBAL_CONF 或者其他 IO操作
        // GLOBAL_CONF.put(key, value);
    }
    //其他 bean 通过这个方法获得系统配置
    public static String getGlobalConfig(String key) {
        return GLOBAL_CONF.get(key);
    }
}

public class DemoBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, 
PriorityOrdered, 
ApplicationContextInitializer<ConfigurableApplicationContext> {
    /**
     *  第二步： 注册 自己的 bean
     *
     * @param beanDefinitionRegistry
     */
    // from BeanDefinitionRegistryPostProcessor interface
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
        beanDefinitionRegistry.registerBeanDefinition("TestService",new RootBeanDefinition(TestService.class));
    }
    // from BeanDefinitionRegistryPostProcessor interface
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
    }
// from PriorityOrdered  interface
    @Override
    public int getOrder() {
        return Ordered.LOWEST_PRECEDENCE - 1;
    }
    /**
     *  第一步 先注册 到 configurableApplicationContext 中
     *
     * @param configurableApplicationContext
     */
    // from ApplicationContextInitializer  interface
    @Override
    public void initialize(ConfigurableApplicationContext configurableApplicationContext) {
        configurableApplicationContext.addBeanFactoryPostProcessor(new DemoBeanDefinitionRegistryPostProcessor());
    }
}