二十八、redis的批量查询

批量查询有一种可以像第一张图一样的根据集合key获取集合value的形式，也可以打开通道，批量的进行redis的操作，然后再关闭通道也是一样的道理，就是减少socket的创建开销。

image.png

    /*
     * (non-Javadoc)
     * @see org.springframework.data.redis.core.RedisOperations#executePipelined(org.springframework.data.redis.core.RedisCallback)
     */
    @Override
    public List<Object> executePipelined(RedisCallback<?> action) {
        return executePipelined(action, valueSerializer);
    }

/**
 * Callback interface for Redis 'low level' code. To be used with {@link RedisTemplate} execution methods, often as
 * anonymous classes within a method implementation. Usually, used for chaining several operations together (
 * {@code get/set/trim etc...}.
 *
 * @author Costin Leau
 */
public interface RedisCallback<T> {

    /**
     * Gets called by {@link RedisTemplate} with an active Redis connection. Does not need to care about activating or
     * closing the connection or handling exceptions.
     *
     * @param connection active Redis connection
     * @return a result object or {@code null} if none
     * @throws DataAccessException
     */
    @Nullable
    T doInRedis(RedisConnection connection) throws DataAccessException;
}

在IDEA里面的类redisConnection中点击编辑器菜单的Naviagate的type hierarchy然后就可以看到类的结构：

image.png

下面给出一个实例：

        List<String> redisKeys = new ArrayList<>();
        redisKeys.add("name");
        redisKeys.add("age");
        redisKeys.add("height");
        List<Object> result = redisTemplate.executePipelined(new RedisCallback<String>() {
            @Override
            public String doInRedis(RedisConnection connection) throws DataAccessException {
                StringRedisConnection src = (StringRedisConnection)connection;
                for(String k:redisKeys){
                    src.get(k);
                }
                return null;
            }
        });