今日份奇葩bug之Only one AsyncConfigurer may exist（场景：老项目引入公司新组件产生的问题）

项目场景：

相关背景：公司原有的各个服务都是单独自己用啥依赖引用啥依赖，版本之间也都参差不齐，包括一些自定义的一些扩展点。现在公司对一些组件进行了封装同时也对一些类进行了统一实现

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问题描述

bug如下： 从中处理出来就是 Only one AsyncConfigurer may exist

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.scheduling.annotation.ProxyAsyncConfiguration': Injection of autowired dependencies failed; nested exception is java.lang.IllegalStateException: Only one AsyncConfigurer may exist
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:405)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1431)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:619)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:410)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1352)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1195)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:582)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:213)
	at org.springframework.context.support.PostProcessorRegistrationDelegate.registerBeanPostProcessors(PostProcessorRegistrationDelegate.java:258)
	at org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:762)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:567)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:771)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:763)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:438)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:339)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1329)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1318)
	at com.persagy.inventory.InventoryApplication.main(InventoryApplication.java:21)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)
Caused by: java.lang.IllegalStateException: Only one AsyncConfigurer may exist
	at org.springframework.scheduling.annotation.AbstractAsyncConfiguration.setConfigurers(AbstractAsyncConfiguration.java:74)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredMethodElement.inject(AutowiredAnnotationBeanPostProcessor.java:724)
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
	... 32 common frames omitted

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原因分析 + 解决方案：

原先是没有 scanBasePackages这个参数的，具体如下，也没报这个错误：
@SpringBootApplication(scanBasePackages = {“XXX”, “XXX”},exclude = {FlywayAutoConfiguration.class})

通过异常显示去搜索这个类发现是个接口，通过查看下级实现类发现是因为公司所封装的与项目中原有的产生冲突。如此便有思路了，只要去去除其一即可

解决方法：

方法一：保留原有项目中原有的话通过如下注解在启动类上加上即可
@ComponentScan(excludeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, classes = {DefaultAsyncTaskConfig.class}))
含义为排除jar包中某一个具体的类，上方的import需要引入类信息
方法二：删除项目中原有的实现类即可

这是老项目引入公司新建的组件问题。从可持续发展角度来看，在项目初始化的时候最好考虑全面在动手，否则遗留全是坑。尤其是微服务，如果说服务量过多之后之前遗留所产生的问题会逐渐显现。