简单且实用的本地缓存（国庆day2）

1 整体流程

2 代码实现

2.1 查询的整体实现代码

/** * 获取记录等级列表 * * @param businessId 租户id * @return List<RecordLevelParam> */ @Transactional(rollbackFor = Exception.class) public List<RecordLevelParam> getRecordLevelList(String businessId) { synchronized (lock) { //1 该租户首次查询，初始化本地缓存 if (!localStorage.containsKey(businessId)) { initialRecordLevelCache(businessId); } try { boolean isUpdate = checkUpdate(businessId); if (isUpdate) { updateRecordLevelCache(businessId); } } catch (Exception e) { } Map<Integer, RecordLevelParam> recordLevelParamMap = localStorage.get(businessId); List<RecordLevelParam> recordLevelParams = new ArrayList<>(); for (Map.Entry<Integer, RecordLevelParam> entity : recordLevelParamMap.entrySet()) { recordLevelParams.add(entity.getValue()); } return recordLevelParams; } }

2.1.1 初始化缓存

/** * 初始化等级缓存 * * @param businessId 租户id */ private void initialRecordLevelCache(String businessId) { synchronized (lock) { //1 从数据中查询等级信息 List<RecordLevelParam> list = prepareRecordLevelParam(businessId); Map<Integer, RecordLevelParam> businessMap = new HashMap<>(list.size()); //2 将等级信息保存到本地 if (list != null && list.size() > 0) { list.forEach(recordLevelParam -> businessMap.put(recordLevelParam.getLevel(), recordLevelParam)); localStorage.put(businessId, businessMap); } else { localStorage.put(businessId, new HashMap<>()); } //3 获取当前租户修改等级的时间戳 Long timeStamp = (Long) redisManager.hget(RECORD_LEVEL_REDIS_HASH_KEY, businessId); Long now = System.currentTimeMillis(); if (null == timeStamp) { redisManager.hset(RECORD_LEVEL_REDIS_HASH_KEY, businessId, now); RECORD_LEVEL_CACHE_STAMP.put(businessId, now); } else { RECORD_LEVEL_CACHE_STAMP.put(businessId, timeStamp); } } }

2.1.2 是否更新本地缓存

/** * 是否更新本地缓存 * * @param businessId 租户id * @throws Exception 异常 */ private boolean checkUpdate(String businessId) throws Exception { Long redisStamp = (Long) redisManager.hget(RECORD_LEVEL_REDIS_HASH_KEY, businessId); Long cashStamp = RECORD_LEVEL_CACHE_STAMP.get(businessId); if (null == cashStamp) { throw new Exception("unfind： " + businessId); } //redis 时间戳大，数据新，需要更新内存 return redisStamp > cashStamp; }

2.1.3 从缓存中获取数据

Map<Integer, RecordLevelParam> recordLevelParamMap = localStorage.get(businessId); List<RecordLevelParam> recordLevelParams = new ArrayList<>(); for (Map.Entry<Integer, RecordLevelParam> entity : recordLevelParamMap.entrySet()) { recordLevelParams.add(entity.getValue()); }

2.2 修改的整体实现代码

@Transactional(rollbackFor = Exception.class) public void updateBusinessLevel(String businessId, Integer recordLevel) throws Exception { // 更新缓存信息 if (localStorage.containsKey(businessId)) { int level = recordLevel; localStorage.get(businessId).put(level, getRecordLevelByBusinessId(businessId, level)); Long now = System.currentTimeMillis(); redisManager.hset(RECORD_LEVEL_REDIS_HASH_KEY, businessId, now); RECORD_LEVEL_CACHE_STAMP.put(businessId, now); } }