If I create default empty based on no archetype Maven project in Eclipse, it will be based on J2SE-1.5.
Maven
Eclipse
J2SE-1.5
@axtavt is right, add source level configuration to your project. But do not configure maven-compiler-plugin, simply put this properties into pom.xml.
maven-compiler-plugin
pom.xml
1.7 1.7
After this refresh maven configuration in Eclipse.