Hot deploy with STS (Eclipse) is not possible

When developing with STS, dev tools are built with maven for hot deployment. At that time, even though [dev tools] is written next to the project name, hot deployment is not performed even if it is saved when the code is modified.

What should I do? The following is a part of the description in pom.xml.

`pom.xml`


 <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-devtools</artifactId>
   <scope>runtime</scope>
   <optional>true</optional>
 </dependency>

The version of STS is Spring Tool Suite 4 for Eclipse

Thank you.