获取设备最大的最近连接时间。改为在数据库里排序好后返回给系统，缓存时间修改为2分钟

--DeviceDao.java 修改方法返回值
--DeviceDao.xml 修改sql，在数据库里排序返回
--DeviceServiceImpl.java 修改缓存时间为2分钟

main/manager-api/src/main/java/xiaozhi/modules/device/dao/DeviceDao.java

@@ -16,6 +16,6 @@ public interface DeviceDao extends BaseMapper<DeviceEntity> {
      * @param agentId 智能体id
      * @return
      */
-    List<Date> getAllLastConnectedAtByAgentId(String agentId);
+    Date getAllLastConnectedAtByAgentId(String agentId);
 
 }

main/manager-api/src/main/java/xiaozhi/modules/device/service/impl/DeviceServiceImpl.java

@@ -260,12 +260,9 @@ public class DeviceServiceImpl extends BaseServiceImpl<DeviceDao, DeviceEntity>
         if (cachedDate != null) {
             return cachedDate;
         }
-        List<Date> list = deviceDao.getAllLastConnectedAtByAgentId(agentId);
-        Date maxDate = Collections.max(list, Comparator.comparing(Date::getTime));
-        // 将结果存入Redis, 存储设备最近最后连接时间，和设备数量
-        redisUtils.set(RedisKeys.getAgentDeviceCountById(agentId), list.size(), 60);
+        Date maxDate = deviceDao.getAllLastConnectedAtByAgentId(agentId);
         if (maxDate != null) {
-            redisUtils.set(RedisKeys.getAgentDeviceLastConnectedAtById(agentId), maxDate, 60);
+            redisUtils.set(RedisKeys.getAgentDeviceLastConnectedAtById(agentId), maxDate, 60 * 2);
         }
         return maxDate;
     }

main/manager-api/src/main/resources/mapper/device/DeviceDao.xml

@@ -3,6 +3,10 @@
 <mapper namespace="xiaozhi.modules.device.dao.DeviceDao">
     <!-- 获取此智能体全部设备的最后连接时间 -->
     <select id="getAllLastConnectedAtByAgentId" resultType="java.util.Date">
-        SELECT last_connected_at FROM ai_device WHERE agent_id = #{agentId}
+        SELECT last_connected_at FROM ai_device
+        WHERE
+            agent_id = #{agentId}
+        order by
+            last_connected_at desc limit 0,1
     </select>
 </mapper>