Redis HMGET
is commonly used when there's a need to retrieve multiple field values of a Hash object in a single command. This comes in handy when you have to fetch multiple related data points stored as fields in a Redis hash.
In Java, you often use Jedis, a popular Redis client, to interact with Redis. Here's an example:
import redis.clients.jedis.Jedis; public class App { public static void main(String[] args) { //Connecting to Redis server on localhost Jedis jedis = new Jedis("localhost"); // Set fields in the hash jedis.hset("user:1001", "name", "John"); jedis.hset("user:1001", "email", "john@example.com"); // Get multiple fields from the hash List<String> result = jedis.hmget("user:1001", "name", "email"); System.out.println(result); // output: [John, john@example.com] } }
In this code, we first connect to the Redis server using Jedis. We then set a couple of fields in a hash identified by the key "user:1001". Using HMGET
, we can retrieve the values of the specified fields in one command.
HMGET
.HMGET
, ensure that the fields you're trying to get actually exist - the command will return null for any non-existing fields.HMGET
: Remember that HMGET
is used for retrieving values from a hash, not for setting them.Q: What happens if the specified key does not exist?
A: If the provided key doesn't exist, Redis HMGET
will return 'nil' for every field specified in the command.
Q: Can I use HMGET
to get fields from multiple hashes at once?
A: No, you can't. HMGET
only works with one hash at a time. If you want to fetch data from multiple hashes, you'll have to use multiple commands or a transaction.
Dragonfly is fully compatible with the Redis ecosystem and requires no code changes to implement.