example.createCriteria().andIntegerfieldEqualTo(5);
int rows = mapper.updateByExample(record, example);
assertEquals(1, rows);
example.clear();
example.createCriteria().andIntegerfieldEqualTo(22);
List<Fieldsonly> answer = mapper.selectByExample(example);
assertEquals(1, answer.size());
record = answer.get(0);
assertNull(record.getDoublefield());