Java 确保某个Bean类被最后执行的几种实现方式

			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
			}

//如下是第一层自定义的BeanDefinitionRegistryPostProcessor BEAN，内部再注册真正用于替换BEAN目的NewBeanDefinitionRegistryPostProcessor BEAN
//author:zuowenjun
@Component
public class FirstDynamicBeanPostProcessor implements BeanDefinitionRegistryPostProcessor {
 @Override
 public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
 BeanDefinitionBuilder beanDefinitionBuilder=BeanDefinitionBuilder.genericBeanDefinition(NewBeanDefinitionRegistryPostProcessor.class);
beanDefinitionRegistry.registerBeanDefinition("newBeanDefinitionRegistryPostProcessor",beanDefinitionBuilder.getBeanDefinition());
 System.out.printf("【%1$tF %1$tT.%1$tL】%s,FirstDynamicBeanPostProcessor.postProcessBeanDefinitionRegistry%n", new Date());
 }

 @Override
 public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
 System.out.printf("【%1$tF %1$tT.%1$tL】%s,FirstDynamicBeanPostProcessor.postProcessBeanFactory%n", new Date());
 }
}

//用于将原依赖的问题Bean替换为同名的新的适配器Bean(下文中所有替换方式最终都要使用该类)
public class NewBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
 @Override
 public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
 System.out.printf("【%1$tF %1$tT.%1$tL】%s,NewBeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry%n",new Date());
 boolean isContainsSpecialBean = ((DefaultListableBeanFactory) beanDefinitionRegistry).containsBean("old问题Bean名称");
 if (isContainsSpecialBean) {
 beanDefinitionRegistry.removeBeanDefinition("old问题Bean名称");
 BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(DemoCompentB.class);
 beanDefinitionBuilder.addConstructorArgValue(((DefaultListableBeanFactory) beanDefinitionRegistry).getBean(NewBeanAdapter.class)); //NewBeanAdapter为继承自old问题Bean的装饰者、适配器类
 AbstractBeanDefinition beanDefinition = beanDefinitionBuilder.getBeanDefinition();
 beanDefinition.setPrimary(true);
 beanDefinitionRegistry.registerBeanDefinition("old问题Bean名称", beanDefinition);
 }

 }

 @Override
 public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
 System.out.printf("【%1$tF %1$tT.%1$tL】%s,NewBeanDefinitionRegistryPostProcessor.postProcessBeanFactory%n",new Date());
 }
}

	private static void sortPostProcessors(List<?> postProcessors, ConfigurableListableBeanFactory beanFactory) {
		Comparator<Object> comparatorToUse = null;
		if (beanFactory instanceof DefaultListableBeanFactory) {
			comparatorToUse = ((DefaultListableBeanFactory) beanFactory).getDependencyComparator();
		}
		if (comparatorToUse == null) {
			comparatorToUse = OrderComparator.INSTANCE;
		}
		postProcessors.sort(comparatorToUse);
	}

//如下是invokeBeanFactoryPostProcessors方法片段：
sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);

@Component
 public static class FirstBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered
 , BeanFactoryAware {

 private BeanFactory beanFactory;

 @Override
 public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
 this.beanFactory=beanFactory;
 }

 @Override
 public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
 ((DefaultListableBeanFactory) beanFactory).setDependencyComparator(new OrderComparator(){
 @Override
 protected int getOrder(Object obj) {
  if (obj instanceof NewBeanDefinitionRegistryPostProcessor){ //如果是NewBeanDefinitionRegistryPostProcessor则将它的排序序号设置为最大
  return Integer.MAX_VALUE;
  }
  return super.getOrder(obj)-1; //其余的全部设为比它小1
 }
 });
 System.out.printf("【%1$tF %1$tT.%1$tL】%s,FirstBeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry%n", new Date());
 }

 @Override
 public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
 System.out.printf("【%1$tF %1$tT.%1$tL】%s,FirstBeanDefinitionRegistryPostProcessor.postProcessBeanFactory%n", new Date());
 }

 @Override
 public int getOrder() {
 return 0;//确保
 }
 }

 public static class BeansImportSelector implements DeferredImportSelector {
 @Override
 public String[] selectImports(AnnotationMetadata importingClassMetadata) {
 return new String[]{NewBeanDefinitionRegistryPostProcessor.class.getName()};
 }
 }

@Configuration
@Import(BeansImportSelector.class)
public class BeansConfig {
 
}

@Component
public class OldBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor,Order {
 
 @Override
 public int getOrder() {
 return 100;
 }
 
 ...
}

@Component
public class NewBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor,Order {
 
 @Override
 public int getOrder() {
 return 101;//只需序号在OldBeanDefinitionRegistryPostProcessor.getOrder之后即可
 }
 
 ...
}