I appears to me that the latest jdbc4 driver is compiled with a wrong
class file format.
unzip -q -c postgresql-9.4-1201.jdbc41.jar org/postgresql/PGStatement.class | od -t x1u1 -N 10
0000000 ca fe ba be 00 00 00 33 00 23
202 254 186 190 0 0 0 51 0 35
The above is OK.
unzip -q -c postgresql-9.4-1201.jdbc4.jar org/postgresql/PGStatement.class | od -t x1u1 -N 10
0000000 ca fe ba be 00 00 00 33 00 23
202 254 186 190 0 0 0 51 0 35
That should be "50" instead of "51".
As a result, loading this driver with Java 1.6.0 results in
java.lang.UnsupportedClassVersionError: org/postgresql/Driver : Unsupported major.minor version 51.0
