网上搜到的以前版本的都是更改Registry...，勾选compiler.automake.allow.when.app.running，然后新版的IDEA的Registry...里没有这个选项，最后找到了解决方案，亲测有效,链接如下：
pom.xml里添加下面所有的即可pom.xml在<project>标签内添加：<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.6.4</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
<configuration>
<fork>true</fork>
<addResources>true</addResources>
</configuration>
</plugin>
</plugins>
</build>子项目pom.xml在<dependencie>标签内添加，注意要在父项目xml里定义版本：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>preferences... -> Compiler
preferences... -> Advanced Settings -> Allow auto-make to start even if developed application is currently running
