mvn命令错误提示，BUILD FAILURE

使用的是myeclipse2015 stable2，maven3.3.9，SDk1.7
现在在命令行下执行mvn -v 版本信息正确；
但是直接执行mvn就错误了，信息如下：
C:\Users\dansan>mvn
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.121 s
[INFO] Finished at: 2016-07-09T20:11:49+08:00
[INFO] Final Memory: 5M/152M
[INFO] ------------------------------------------------------------------------
[ERROR] No goals have been specified for this build. You must specify a valid li
fecycle phase or a goal in the format : or <plugin-group-id

:[:]:. Available lifecycle phases are
: validate, initialize, generate-sources, process-sources, generate-resources, p
rocess-resources, compile, process-classes, generate-test-sources, process-test-
sources, generate-test-resources, process-test-resources, test-compile, process-
test-classes, test, prepare-package, package, pre-integration-test, integration-
test, post-integration-test, verify, install, deploy, pre-clean, clean, post-cle
an, pre-site, site, post-site, site-deploy. -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e swit
ch.
[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 rea
d the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/NoGoalSpecifie
dException

这个到底是什么问题，已经在网络上找了好多问题，都没有解决