Java8 Map+函数式接口 实现策略者模式实例

    // 定义函数式接口
    @FunctionalInterface
    interface MapFunction {
        R apply(A a, B b, C c, D d, E e, F f);
    }

    /**
     * 定义的策略map
     */
    private Map> ruleMap;

    // 策略map初始化
    @PostConstruct
    public void combineTargetRuleInit() {
        ruleMap.put(CombineTargetRuleEnum.RECENT.getCode(), (deviceId, tableName, fieldName, startDate, endDate, isFirst) -> combineTargetRuleService.getRecentValue(deviceId, tableName, fieldName, startDate, endDate, isFirst));
        ruleMap.put(CombineTargetRuleEnum.FARTHEST.getCode(), (deviceId, tableName, fieldName, startDate, endDate, isFirst) -> combineTargetRuleService.getFarthestValue(deviceId, tableName, fieldName, startDate, endDate, isFirst));
        ruleMap.put(CombineTargetRuleEnum.AVG.getCode(), (deviceId, tableName, fieldName, startDate, endDate, isFirst) -> combineTargetRuleService.getAvgValue(deviceId, tableName, fieldName, startDate, endDate));
        ruleMap.put(CombineTargetRuleEnum.MAX.getCode(), (deviceId, tableName, fieldName, startDate, endDate, isFirst) -> combineTargetRuleService.getMaxValue(deviceId, tableName, fieldName, startDate, endDate));
        ruleMap.put(CombineTargetRuleEnum.MIN.getCode(), (deviceId, tableName, fieldName, startDate, endDate, isFirst) -> combineTargetRuleService.getMinValue(deviceId, tableName, fieldName, startDate, endDate));
    }



    /**
     * 实现业务逻辑
     */
    private IndicatorEntityDTO getRelatedTargetValue(Date keyTargetTime, CombineTargetEntity combineTargetEntity,
                                                     Integer deviceId) {
        // 获取时间范围内的所有数据，如果主指标先到，时间范围则取主指标之后，如果后到，时间范围则取主指标之前
        String fieldName = DataConversionUtil.humpToUnderline(combineTargetEntity.getRelatedTarget());
        String tableName = Constant.DFS_RECORD_DEVICE_ + fieldName;
        // 如果开始和结束时间都为0，则取最新的一条数据，否则按配置的时间单位参数进行查询
        if (combineTargetEntity.getStart() == 0 && combineTargetEntity.getEnd() == 0) {
            return indicatorService.getNewVal(tableName, fieldName, deviceId);
        } else {
            String startDate = null;
            String endDate = null;
            int start = combineTargetEntity.getFirst() ? combineTargetEntity.getStart() : -combineTargetEntity.getEnd();
            int end = combineTargetEntity.getFirst() ? combineTargetEntity.getEnd() : -combineTargetEntity.getStart();
            switch (combineTargetEntity.getUnit()) {
                case Constant.HOUR:
                    startDate = DateUtil.format(DateUtil.addHour(keyTargetTime, start), DateUtil.DATETIME_FORMAT);
                    endDate = DateUtil.format(DateUtil.addHour(keyTargetTime, end), DateUtil.DATETIME_FORMAT);
                    break;
                case Constant.MINUTE:
                    startDate = DateUtil.format(DateUtil.addMin(keyTargetTime, start), DateUtil.DATETIME_FORMAT);
                    endDate = DateUtil.format(DateUtil.addMin(keyTargetTime, end), DateUtil.DATETIME_FORMAT);
                    break;
                case Constant.SECOND:
                    startDate = DateUtil.format(DateUtil.addSec(keyTargetTime, start), DateUtil.DATETIME_FORMAT);
                    endDate = DateUtil.format(DateUtil.addSec(keyTargetTime, end), DateUtil.DATETIME_FORMAT);
                    break;
                default:
                    break;
            }
            // 时间范围内的数据根据规则进行数据绑定
            return ruleMap.get(combineTargetEntity.getStrategy()).apply(deviceId, tableName, fieldName, startDate, endDate, combineTargetEntity.getFirst());
        }
    }

注解说明：

@FunctionalInterface

@PostConstruct


详解：
 策略模式之Map+函数式接口