//根據(jù)id查詢美食信息  
public GoodsVO loadGoodsInfoById(Long id) {
  //從redis中拿用戶信息
  Object obj = redisTemplate.opsForValue().get(GOODS_KEY + id);
  if(obj == null) {
      //如果redis中不存在，就從數(shù)據(jù)庫(kù)中獲取
      GoodsVO goods = loadGoodsFromDb(id);
      //將結(jié)果保存到redis中
      redisTemplate.opsForValue().set(GOODS_KEY+id,JSONUtil.toJsonPrettyStr(goods));
      return fileUser;
  }
  return JSONUtil.toBean(obj.toString(), GoodsVO.class);
}

//編輯美食信息
public void modifyGoodsById(GoodsVO goodsVO) throws Exception{
    //刪除緩存
    redisTemplate.delete(GOODS_KEY + goodsVO.getId());
    //更新用戶信息
    goodsMapper.updateById(goodsVO);
    //刪除緩存
    Thread.sleep(1000);
    redisTemplate.delete(GOODS_KEY + goodsVO.getId());
}

//根據(jù)id查詢美食信息  
public GoodsVO loadGoodsInfoById(Long id) {
  //從redis中拿用戶信息
  Object obj = redisTemplate.opsForValue().get(GOODS_KEY + id);
  if(obj == null) {
      //如果redis中不存在，就從數(shù)據(jù)庫(kù)中獲取
      GoodsVO goods = loadGoodsFromDb(id);
      return fileUser;
  }
  return JSONUtil.toBean(obj.toString(), GoodsVO.class);
}
//查詢緩存中沒(méi)有，這時(shí)候就要去數(shù)據(jù)庫(kù)中查詢
public String getGoodInfoFromDb(Long id) {
    //此時(shí)這里要加的鎖和 modifyGoodsById()方法加的應(yīng)該是同一把鎖，這樣才能保證雙寫一致性
    boolean lock = redisLock.tryLock(GOODS_KEY+id);
    if(!lock) {
    	//獲取鎖失敗,嘗試從緩存中獲取
    	Object obj = redisTemplate.opsForValue().get(GOODS_KEY + id);
      if(obj != null){
          return JSONUtil.toBean(obj.toString(), GoodsVO.class);
      }else{
          //直接返回一個(gè)操作頻繁的信息給前端
          throw new GloableException("訪問(wèn)頻繁，請(qǐng)稍后再試");
      }
    }
    try{
        //獲取到鎖了
        //嘗試從緩存中拿
        Object obj = redisTemplate.opsForValue().get(GOODS_KEY + id);
        if(obj != null) {
            return JSONUtil.toBean(obj.toString(), GoodsVO.class);
        }
        //緩存中沒(méi)有，從MySql中拿
        GoodsVO goods = goodsMapper.selectById(id);
        if(goods == null) {
            //為了解決緩存穿透的問(wèn)題
            redisTemplate.opsForValue().set(GOODS_NULL_KEY + id);
            return null;
        }
        //將數(shù)據(jù)庫(kù)查到的數(shù)據(jù)放到緩存中
        redisTemplate.opsForValue().set(GOODS_KEY+id,JSONUtil.toJsonPrettyStr(goods));
        return goods;
    }finally{
       //釋放鎖
       redisLock.unLock(GOODS_KEY+goodsVO.getId());
    }
}

//編輯美食信息
public void modifyGoodsById(GoodsVO goodsVO) throws Exception{
    //嘗試獲取鎖
    boolean lock = redisLock.tryLock(GOODS_KEY+goodsVO.getId());
    if(!lock) {
      	//直接返回一個(gè)操作頻繁的信息給前端
        throw new GloableException("更新數(shù)據(jù)失敗,請(qǐng)稍后再試.....");
    }
    try{
        //獲取到鎖了
        //更新用戶信息
        goodsMapper.updateById(goodsVO);
        //更新完之后，將數(shù)據(jù)庫(kù)最新的數(shù)據(jù)更新到緩存中
        redisTemplate.opsForValue().set(GOODS_KEY+id,JSONUtil.toJsonPrettyStr(goodsVO));
    }finally{
        //釋放鎖
        redisLock.unLock(GOODS_KEY+goodsVO.getId());
    }
}