新建的项目导入了：spring-boot-starter-parent
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.7.1</version> <relativePath/> <!-- lookup parent from repository --> </parent>
spring-boot-starter-parent又依赖了：spring-boot-dependencies
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-dependencies</artifactId> <version>2.7.1</version> </parent>
spring-boot-dependencies里对使用的依赖版本进行了默认的配置：
<properties> <activemq.version>5.16.5</activemq.version> <antlr2.version>2.7.7</antlr2.version> </properties>
主程序类：@SpringBootApplication
