java-策略模式的简单应用

我以我在实际项目中的应用举例

场景如下：MQTT收到消息之后，根据不同的标识（operator）去进行不同的处理

1.新建接口MqttCallBackService<T> 

public interface  MqttCallBackService<T> {
　　　//形参的转换方法
    T parseMessageToFunctionParam(JSONObject messageInfo);
　　//统一的处理方法
    void dealMqttMessageData(T jsonMessage);
　　//获取操作标识 作为后续策略key使用，这里因为场景需要才定义的，也可不定义
    String getOperator();

}
2.所有的实现了均应实现MqttCallBackService<T>接口

@Service //心跳处理实现
public class HeartBeatCallBackServiceImpl implements MqttCallBackService<HeartBeatVo> {

    @Autowired
    private DeviceManagerService deviceManagerService;

    @Override
    public HeartBeatVo parseMessageToFunctionParam(JSONObject messageInfo) {
        return JSONUtil.toBean(messageInfo, HeartBeatVo.class);
    }

    @Override
    @Transactional
    public void dealMqttMessageData(HeartBeatVo heartBeatVo) {
        DeviceManagerSaveBo deviceManager = new DeviceManagerSaveBo();
        deviceManager.setDeviceId(heartBeatVo.getFacesluiceId());
        deviceManager.setHeartbeatTime(DateUtil.stringHHmmss2Date(heartBeatVo.getTime()));
        this.deviceManagerService.updateHeartByDeviceId(deviceManager);
    }

    @Override
    public String getOperator() {
        return "HeartBeat";
    }
}

@Service
@Slf4j //下线处理实现
public class OfflineCallBackServiceImpl implements MqttCallBackService<HeartBeatVo> {
    @Override
    public HeartBeatVo parseMessageToFunctionParam(JSONObject messageInfo) {
        return JSONUtil.toBean(messageInfo, HeartBeatVo.class);
    }

    @Override
    public void dealMqttMessageData(HeartBeatVo heartBeatVo) {
        log.info("处理下线开始");
        log.info("设备id为：" + heartBeatVo.getFacesluiceId()+" 下线；下线时间为："+heartBeatVo.getTime());
        log.info("处理下线结束");
    }

    @Override
    public String getOperator() {
        return "Offline";
    }
}

3新建策略管理StrategyFactoryHandler
在此配置策略map

@Component
@Slf4j
public class StrategyFactoryHandler {

    private final Map<String, MqttCallBackService> strategyMaps = new ConcurrentHashMap<>();

    @Autowired //通过@Autowired 注解 可以自动获取到MqttCallBackService的所有实现并成为集合  按我设定的操作对应具体实现类型

    public StrategyFactoryHandler(List<MqttCallBackService> mqttCallBackServices) {
        mqttCallBackServices.forEach(e -> {
            strategyMaps.put(e.getOperator(), e);
        });

        log.debug("strategyMaps初始化：{}", strategyMaps);
    }
　　//根据操作获取具体的实现
    public MqttCallBackService getService(String operate) {
        return strategyMaps.get(operate);
    }

}

4 调用：注入

@Autowired
private StrategyFactoryHandler strategyFactoryHandler;

获取返回消息中的operator ，根据operator 获取实现 ，再调用具体的处理方式进行处理

//String operator = commonVo.getOperator();

String operator = “Offline”;//HeartBeat

MqttCallBackService invokeHandler = strategyFactoryHandler.getService(operator);

JSONObject info = commonVo.getInfo();

//此方法是进行参数的转换

//invokeHandler.parseMessageToFunctionParam(info)
此处调用就会根据具体返回的实现类进行各自的参数处理

invokeHandler.dealMqttMessageData(invokeHandler.parseMessageToFunctionParam(info));

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