导入eclipse有Unbound classpath variable: 'M2_REPO报错的解决方法

Eclipse maven of the project reported in Unbound classpath variable: 'M2_REPO /**/***/***. jar' 

But in fact the jar is present in my local machine's directory , oh MAVEN: 

C: / Documents and Settings / administrator /. M2 / repository / ** / *** / ***. jar 

Description sure M2_REPO Eclipse not recognize this parameter, so it needs to add: 

Eclipse-> Windows-> Preferences-> java-> Build Path-> Classpath Variables 

new one, name of course M2_REPO, attributes selected folder, 

Point to C: / Documents and Settings / administrator /. M2 / repository