maven3 依赖的升级 （强制）

[WARNING] Missing POM for org.apache.mahout.hadoop:hadoop-core:jar:0.20.2
[WARNING] An error occurred during dependency resolution.
    Failed to retrieve org.apache.mahout.hadoop:hadoop-core-0.20.2
Caused by: Failure to find org.apache.mahout.hadoop:hadoop-core:jar:0.20.2 in http://localhost:8080/nexus/content/groups/public/ was cached in the local reposit
ory, resolution will not be reattempted until the update interval of public-repo has elapsed or updates are forced

Try downloading the file manually from the project website.

 我在用hadoop时出现了以上异常（前提我刚把maven2.2 升级成maven3）。

原因是我之前用的是hadoop0.20.1 现在想换成 0.20.2 版本

细读了下worning 信息，发现maven3 必须强制  -U 来强制jar 升级  否则会吃先这样的警告。

于是乎 执行 mvn eclipse:eclipse -U  便下载了0.20.2 版本的jar。