mvn报错：No goals have been specified for this build

选择【Run As】-【Maven build】的时候，报：
[INFO] Scanning for projects…[INFO]
[INFO] BUILD FAILURE[INFO]
[INFO] Total time: 0.109s[INFO] Finished at: Wed Apr 13 11:04:20 CST 2011[INFO] Final Memory: 1M/4M[INFO]
ERROR] No goals have been specified for this build. You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>. Available lifecycle phases are: validate, initialize, generate-sources, process-sources, generate-resources,
process-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-site, site, post-site, site-deploy,
pre-clean, clean, post-clean. -> [Help 1][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/NoGoalSpecifiedException 

eclipse安装的maven插件是m2eclipse，在控制台使用命令mvn compile并未报错。后在pom.xml文件<build>标签里面加 上<defaultGoal>compile</defaultGoal>即可。

其实使用命令行时就已经指定了phase，而使用m2eclipse的【Run As】-【Maven build】时并未为其指定goal或phase，所以才报这个错误。