1.

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

2.

3.

4.

-------------------------------------------

報錯：

Error:Maven Resources Compiler: Maven project configuration required for module 'spring-devtool' isn't available. Compilation of Maven projects is supported only if external build is started from an IDE.