@Setter
@Getter
@Accessors(chain = true)
@JSONType(naming = PropertyNamingStrategy.SnakeCase)
public class Params {

    private boolean withFields;

    private List<String> verificationIds;
}

@org.junit.Test
    public void test() {
        Params params = new Params()
                .setVerificationIds(Arrays.asList(new String[]{"a", "b"}))
                .setWithFields(true);

        String json = JSON.toJSONString(params);
        log.debug(json);

        params = JSON.parseObject(json, Params.class);
        log.debug(JSON.toJSONString(params));
    }

 - {"verification_ids":["a","b"],"with_fields":true}
 - {"with_fields":true}