修改

.idea/modules.xml

@@ -4,7 +4,6 @@
     <modules>
       <module fileurl="file://$PROJECT_DIR$/demo/demo.iml" filepath="$PROJECT_DIR$/demo/demo.iml" />
       <module fileurl="file://$PROJECT_DIR$/firstproject.iml" filepath="$PROJECT_DIR$/firstproject.iml" />
-      <module fileurl="file://$PROJECT_DIR$/firstproject.iml" filepath="$PROJECT_DIR$/firstproject.iml" />
     </modules>
   </component>
 </project>

demo/src/main/java/com/example/demo/Dao/paymentMapper.java

@@ -1,6 +1,5 @@
 package com.example.demo.Dao;
 
-import com.example.demo.bean.Manager;
 import com.example.demo.bean.Repayment;
 import org.apache.ibatis.annotations.Insert;
 import org.apache.ibatis.annotations.Mapper;

demo/src/main/java/com/example/demo/DemoApplication.java

@@ -1,6 +1,5 @@
 package com.example.demo;
 
-import org.mybatis.spring.annotation.MapperScan;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;