pom.xml中引入依赖版本号省略问题

1. 靠前位置设置了版本属性

   <properties>
       <tomcat.version>9.0.63</tomcat.version>
   </properties>
   
   <dependencyManagement>
       <dependencies>
       	<dependency>
           	<groupId>org.apache.tomcat</groupId>
           	<artifactId>tomcat-jdbc</artifactId>
           	<version>${tomcat.version}</version>
         	</dependency>
   	</dependencies>
   </dependencyManagement>
   

2. 继承了父依赖中的版本属性

   <dependencies>
   	<dependency>
   		<groupId>org.springframework.boot</groupId>
   		<artifactId>spring-boot-starter-web</artifactId>
   	</dependency>
   </dependencies>