If you are using c3p0 for db connection pooling and also using Java 6, be sure to use version c3p0-0.9.5-pre8, no the latest version c3p0-0.9.5-pre9. Starting from version c3p0-0.9.5-pre9, c3p0 interface com.mchange.v2.c3p0.PooledDataSource extends from Java 7's java.lang.AutoClosable, so c3p0 c3p0-0.9.5-pre9 cannot run on Java 6. See source code 0.9.5-pre9 and 0.9.5-pre8 for the difference.