<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-devtools</artifactId>
   <optional>true</optional>
</dependency>
<plugin>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-maven-plugin</artifactId>
   <configuration>
      <fork>true</fork> <!-- 如果没有该配置，devtools不会生效 -->
   </configuration>
</plugin>