项目记录：利用Redis实现缓存以提升查询效率

一、概述

当我们查询所有数据时，如果缓存中没有，则去数据库查询，如果有，直接查缓存的数据就行。注意定期更新缓存数据。

二、主体代码

    private static final String ROOM_SCHEDULES_HASH = "RoomSchedules";@Overridepublic List<RoomSchedule> getAllRoomSchedules()  {BoundHashOperations<String, String, String> hashOps = stringRedisTemplate.boundHashOps(ROOM_SCHEDULES_HASH);if (hashOps.size() == 0) {List<RoomSchedule> roomSchedules = roomScheduleMapper.getAllRoomSchedules();for (RoomSchedule roomSchedule : roomSchedules) {ObjectMapper objectMapper = new ObjectMapper();try {String json = objectMapper.writeValueAsString(roomSchedule);hashOps.put(roomSchedule.getId().toString(), json);} catch (Exception e) {e.printStackTrace();}}stringRedisTemplate.expire(ROOM_SCHEDULES_HASH, 3, TimeUnit.MINUTES);  // 设置有效期为三分钟return roomSchedules;} else {Map<String, String> entries = hashOps.entries();List<RoomSchedule> roomSchedules = new ArrayList<>();for (String json : entries.values()) {try {ObjectMapper objectMapper = new ObjectMapper();RoomSchedule roomSchedule = objectMapper.readValue(json, RoomSchedule.class);roomSchedules.add(roomSchedule);} catch (Exception e) {e.printStackTrace();}}return roomSchedules;}}

BoundHashOperations是绑定键值的方法，意味着之后的操作都是对此键进行操作。

ObjectMapper类提供了一系列json序列化和反序列化的操作。

缓存更新操作是通过设置TTL有效期来实现的。