「黑马点评」十、附近商户

GEO 数据结构

Geolocation 代表地理坐标，以下为常见坐标

练习 Redis GEO

添加以下信息
- 北京南站 116.378248 39.865275
- 北京站 116.42803 39.903738
- 北京西站 116.322287 39.893729
计算北京西站到北京站的距离
搜索天安门 116.397904 39.909005 附近 10km 内的所有火车站，并按照距离升序排列

添加命令 GEOADD key longitude latitude member [longitude latitude member] 示例 GEOADD g1 116.378248 39.865275 bjn 116.42803 39.903738 bjz 116.322287 39.893729 bjx

实际上观察 Redis 可以发现 GEO 底层使用的是 ZSET，value 即为 member，经纬度转换成数字存储为 score；add 到顺序也是，先 score/geo 后 value/member

距离命令 GEODIST key member1 member2 示例 GEODIST g1 bjn bjx [m/km]

搜索命令 GEOSEARCH key FROMLONLAT longitude latitude BYRADIUS radius m/km WITHDIST 示例 GEOSEARCH g1 FROMLONLAT 116.397904 39.909005 BYRADIUS 10 km WITHDIST

哈希：将经纬度转化为二进制再对应成 hash 命令 GEOHASH key member 示例 GEOHASH g1 bjz

导入店铺位置到 Redis

按照商户类型分组，以 typeId 作为 key 存入 GEO 集合

演示了如何利用 java 代码，将数据库的商户一次性按类型分组导入到 Redis

@Test
void loadShopData() {
    // 1.查询店铺信息
    List<Shop> list = shopService.list();
    // 2.把店铺分组，按照typeId分组，typeId一致的放到一个集合
    Map<Long, List<Shop>> map = list.stream().collect(Collectors.groupingBy(Shop::getTypeId));
    // 3.分批完成写入Redis
    for (Map.Entry<Long, List<Shop>> entry : map.entrySet()) {
        // 3.1.获取类型id
        Long typeId = entry.getKey();
        String key = SHOP_GEO_KEY + typeId;
        // 3.2.获取同类型的店铺的集合
        List<Shop> value = entry.getValue();
        List<RedisGeoCommands.GeoLocation<String>> locations = new ArrayList<>(value.size());
        // 3.3.写入redis GEOADD key 经度 纬度 member
//            for(Shop shop : value){ // 这样要建立 value.size() 次连接，慢
//                stringRedisTemplate.opsForGeo().add(key,new Point(shop.getX(),shop.getY()),shop.getId().toString()) ;
//            }
        for (Shop shop : value) {
            locations.add(new RedisGeoCommands.GeoLocation<>(
                    shop.getId().toString(),
                    new Point(shop.getX(), shop.getY())
            ));
        }
        stringRedisTemplate.opsForGeo().add(key, locations);
    }
}

附近商户实现

获取附近商户：GET /api/shop/of/type?&typeId={typeId}&current={currentPage}&x={longitude}&y={latitude}

注意这里批量查询 shop 也需要 order by filed('id', ids)，保证按照距离最近的顺序返回

这里 Redis 使用的命令只能设置 radius，并且能限制查询个数 limit，但是无法跳过 from，所以手动截取分页，利用 steam 流 skip(from)

这里要注意哪怕 list 不为空，跳过了 from 个也可能为空，所以需要做判断

@GetMapping("/of/type")
public Result<List<Shop>> queryShopByType(
        @RequestParam("typeId") Integer typeId,
        @RequestParam(value = "current", defaultValue = "1") Integer current,
        @RequestParam(value = "x", required = false) Double x,
        @RequestParam(value = "y", required = false) Double y
) {
    return Result.success(shopService.queryShopByType(typeId, current, x, y));
}

@Override
public List<Shop> queryShopByType(Integer typeId, Integer current, Double x, Double y) {
    if (x == null || y == null) {
        int offset = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
        List<Shop> shopList = shopMapper.selectByType(typeId, offset, SystemConstants.DEFAULT_PAGE_SIZE);
        return shopList;
    }
    int from = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
    int end = current * SystemConstants.DEFAULT_PAGE_SIZE;
    String key = RedisConstants.SHOP_GEO_KEY + typeId;
    GeoResults<RedisGeoCommands.GeoLocation<String>> result = stringRedisTemplate.opsForGeo() // GEOSEARCH key BYLONLAT x y BYRADIUS 10 km WITHDIST
        .search(
            key, 
            GeoReference.fromCoordinate(x, y),
            new Distance(5000),
            RedisGeoCommands.GeoSearchCommandArgs.newGeoSearchArgs().includeDistance().limit(end)
        );
    if (result == null) {
        return Collections.emptyList();
    }
    List<GeoResult<RedisGeoCommands.GeoLocation<String>>> list = result.getContent();
    if (list.size() <= from) {
        return Collections.emptyList();
    }
    List<Long> ids = new ArrayList<>(end - from);
    Map<String, Distance> distanceMap = new HashMap<>(end - from);
    list.stream().skip(from).forEach(geoResult -> {
        String shopIdStr = geoResult.getContent().getName();
        ids.add(Long.valueOf(shopIdStr));
        Distance distance = geoResult.getDistance();
        distanceMap.put(shopIdStr, distance);
    });
    List<Shop> shops = shopMapper.selectShopByIds(ids);
    shops.forEach(shop -> {
        shop.setDistance(distanceMap.get(shop.getId().toString()).getValue());
    });
    return shops;
}