A utility for assembling SQL conditional clause
Usage 1.
FilterHelper helper = new FilterHelper(); helper .and("x", 1) .and("y", 2); helper.clearFilter();
==> returns sql: "x = '1' AND y = '2'"
Usage 2.
FilterHelper helper = new FilterHelper(); helper .and("x", 1) .and("y", 2) .begin() .and("a", 0) .or("a", Operator.IS_NULL) .end() .and("z", 3); helper.clearFilter();
==> returns sql: "x = '1' AND y = '2' AND (a = '0' OR a IS NULL) AND z = '3'"