spring boot+mybatis报错mapper无法注入

搭建spring boot项目时启动出现的问题，先来看异常片段：

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-06-04 09:32:21.462 ERROR 18900 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

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APPLICATION FAILED TO START
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Description:

Field userMapper in com.drefore.demozw.admin.service.TestOneService required a bean of type 'com.drefore.demozw.mapper.UserMapper' that could not be found.

The injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.Autowired(required=true)

Action:

Consider defining a bean of type 'com.drefore.demozw.mapper.UserMapper' in your configuration.

提示mapper未找到无法注入

在网上搜索了一圈有说项目结构的问题，application入口类应该放在 mapper同级目录下，可是我的目录结构没问题，可能别的地方适用，在我这只好另找办法，最后在application入口类上添加该注解解决问题

@MapperScan("mapper文件夹路径")