Maven依赖传递排除指定的依赖关系

应用场景：projectA 依赖projectB, projectB 依赖projectC时

projectA中pom.xml
<groupId>com.cn.projectA</groupId>
<artifactId>projectA</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
	<dependency>
		<groupId>com.cn.projectB</groupId>
		<artifactId>projectB</artifactId>
		<version>1.0B</version>
		<!--方案一：使用execusions排除A与C的依赖  -->
		<exclusions>
			<exclusion>
				<groupId>com.cn.projectC</groupId>
				<artifactId>projectC</artifactId>
			</exclusion>
		</exclusions>
	</dependency>
</dependencies>

projectB中的pom.xml
<groupId>com.cn.projectB</groupId>
	<artifactId>projectB</artifactId>
	<version>1.0B</version>
	<dependencies>
		<dependency>
			<groupId>com.cn.projectC</groupId>
			<artifactId>projectC</artifactId>
			<version>1.0C</version>
			<!--依赖传递选项，默认为false为依赖，ture为不依赖传递
			方案二：通过optional设置自动或手动,排除A与C的依赖
				-->
			<optional>false</optional>
		</dependency>
	</dependencies>
	
	
	projectC的pom.xml
	<groupId>com.cn.projectC</groupId>
	<artifactId>projectC</artifactId>
	<version>1.0C</version>