缓存简单实现

老翟笔记今日分享的是:缓存简单实现

时间和次数触发更新;有缓存雪崩的情况,更新有更新锁,还是有点并发问题,不适用于高并发,不严谨,简单实现. /*** 有一个更新就可以了,不要都更新 <br/>* 切记：获取锁后在finally里释放该锁！！！否则将导致无法获取到锁来更新缓存。<br/>* eg:<br/>* if(refreshLock.tryLock(1, TimeUnit.SECONDS)){try{}finally{refreshLock.unlock();}}*/private static volatile Lock refreshLock = new ReentrantLock();private Map<String,List<String>> cacheXXobjMap = new Hashtable<String,List<String>>();private volatile boolean isRefreshSuccess = false;private volatile boolean isRefreshing = false;private volatile long refreshDateTime = 0;private volatile int requestCount = 0; private Stirng key = "xxKey";@RequestMapping("/getXXXObjList")@ResponseBodypublic List<String> getXXXObjList(HttpSession session, HttpServletRequest request,@RequestParam Map<String, Object> params) {boolean isrequestTooMuch = requestCount > 100;if(isrequestTooMuch) {requestCount = 0;}requestCount++;//如果刷新时间小于1小时且访问次数小于100且已经刷新完成可以直接从缓存中取,否则从数据库中查询并更新缓存if(System.currentTimeMillis()-refreshDateTime<3600000&&!isrequestTooMuch&&isRefreshSuccess&&!isRefreshing) {return cacheXXobjMap.get(key);}isRefreshing = true;List<Object> objs = new ArrayList<Object>();try {objs = jobService.getXXXObjList(params);try {if (refreshLock.tryLock(500, TimeUnit.MILLISECONDS)) {//更新缓存try {cacheXXobjMap.put(key, objs);} finally {refreshLock.unlock();}refreshDateTime=System.currentTimeMillis();isRefreshSuccess = true;}} catch (InterruptedException e) {e.printStackTrace();}return objs} finally {isRefreshing = false;}}  

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