在默认情况下，如何配置Maven来使用JDK6，但需要的是JDK7 ?

I have both JDK 1.6 and 1.7 installed on my system (Linux, under the /opt directory). I've added the bin directory for JDK 1.6 in my path, so that's the version of Java used by default.I have both JDK 1.6 and 1.7 installed on my sys