<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>${spring-boot.version}</version>
            <type>pom</type><!--BOM 文件以 POM 形式存在的,它不包含实际的代码,只包含了各种依赖的版本声明-->
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>