JAVA8-Predicate functions use

JAVA8-Predicate functions use

The main explanation

Predicate accepts an input parameter and returns a boolean result. The interface comprises a plurality of default methods to be combined into other complex Predicate logic (such as: and, or, not). Interface parameters may be used to verify the request, determine whether there are changes to the new and old data update operation. add- and, or- or, negate- non

Title common method

1. Analyzing boolean test (T t);

Real scene

General check request parameters, determines whether to change the data

    public class CommonUtils {
    //参数校验
    public static <T> void checkParams(T t, Map<String, Predicate<T>> map) {
        if (isNotEmpty(map)) {
            map.entrySet().forEach(r -> {
                if (r.getValue().test(t))
                    throw new PandaException(PandaCodes.BAD_PARAM, r.getKey());
            });
        }
    }
    //数据变更校验
    public static <T> boolean checkDataIsChange(T t, List<Predicate<T>> list) {
        if (isNotEmpty(list)) {
            return list.stream().anyMatch(r -> r.test(t));
        }
        return false;
    }
}

Such as: parameter calibrating

private Map<String,Predicate<SkuPlatPriceVo>> getCheckParamRules() {
    Map<String, Predicate<SkuPlatPriceVo>> map = new HashMap<>();
        map.put("平台现价需要为0-无穷大", r -> r.getPlatePrice() < 0);
        map.put("平台的platform不能为空", r -> ParamChecker.isBlank(r.getPlatform()));
    return map
}
//校验页面传入的skuPlatPriceVo参数：CommonUtils.checkParams(skuPlatPriceVo,getCheckParamRules());

Such as: data change check

private List<Predicate<SkuPlatPriceVo>> getCheckDataIsChangeRules(PcCustomPriceDTO oldData) {
        List<Predicate<SkuPlatPriceVo>> list = new ArrayList<>();
        list.add(r -> oldData.getPrice() != null && r.getPlatePrice() != oldData.getPrice());
        list.add(r -> oldData.getRebate() != null && r.getRebate() != oldData.getRebate());
        return list;
}

//校验页面传入的更新操作skuPlatPriceVo数据是否需要发生变更要执行数据库update操作
if(CommonUtils.checkDataIsChange(skuPlatPriceVo,getCheckDataIsChangeRules(dto))){
    //数据库数据更新
}