这个问题很简单，网上也有很多的答案。以下是报错的信息：

[INFO] Scanning for projects...
[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[ERROR] 'packaging' with value 'jar' is invalid. Aggregator projects require 'pom' as packaging. @ line 10, column 16
@
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR]
[ERROR]   The project cn.xxx:1.0-SNAPSHOT (E:\das-code\spring-cloud-demo\pom.xml) has 1 error
[ERROR]     'packaging' with value 'jar' is invalid. Aggregator projects require 'pom' as packaging. @ line 10, column 16
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/ProjectBuildingException

原因分析

其原因是：当多个父-子结构的maven工程使用maven package打包的时候， 父节点module不能把packaging 声明为jar，应当声明为pom，表明这是一个pom工程，不生成jar，只管理工程结构。

解决办法

将父类pom.xml中的

<packaging>jar</packaging>

改为：

<packaging>pom</packaging>

注意：子module仍然需要声明为jar，因为子module是实质执行代码指令的module。