启动时错误如下：

org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [com.xxx.xx.BootApplication]; nested exception is org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name ‘userController’ for bean class [com.xxx.xx.controller.web.UserController] conflicts with existing, non-compatible bean definition of same name and class [com.xxx.xx.controller.api.UserController]
at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:189) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:319) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:236) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:280) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:96) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:707) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:533) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) [spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) [spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:405) [spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.7.RELEASE.jar:2.3.7.RELEASE]
at com.xxx.xx.BootApplication.main(BootApplication.java:14) [classes/:na]
Caused by: org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name ‘userController’ for bean class [com.xxx.xx.controller.web.UserController] conflicts with existing, non-compatible bean definition of same name and class [com.xxx.xx.controller.api.UserController]
at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.checkCandidate(ClassPathBeanDefinitionScanner.java:349) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.doScan(ClassPathBeanDefinitionScanner.java:287) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ComponentScanAnnotationParser.parse(ComponentScanAnnotationParser.java:132) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:296) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:250) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:207) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:175) ~[spring-context-5.2.12.RELEASE.jar:5.2.12.RELEASE]
… 14 common frames omitted

Process finished with exit code 1

解决：

上面意思是，加载注解的Bean时有同名类，因此不被允许。
错误信息也列出了同名类的具体位置：[com.xxx.xx.controller.api.UserController]，[com.xxx.xx.controller.web.UserController]，将其中一个文件名和类名改名即可，这是springboot常见的错误。