This is how I got 1.7 to work with Eclipse. I hope it helps.
- I Downloaded the latest OpenJDK 1.7 universal (32/64 bits) JDK
from Mac OS/X branch from http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html - copied the jdk to /Library/Java/JavaVirtualMachines/ next to the
default 1.6.0 one - In Eclipse > Preferences > Java > Installed JREs you add a new one, of type MacOS X VM, and set the home as /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home and
name Java SE 7 (OpenJDK) - Click Finish
- Set the added JRE as default
that should be it 🙂