CODEWITHSUNDEEP
javaredislettuce
tcfritchman
tcfritchman

Reputation: 77

How do you initialize the MapScanCursor in Lettuce Redis client library?

I am trying to do an HSCAN using Lettuce's synchronous commands. The problem is that I can't figure out the correct way of initializing the MapScanCursor. I've had no success with the constructor, and MapScanCursor.INITIAL gives type ScanCursor (no luck casting that to MapScanCursor either).

Here is an example:

RedisClient redisClient = RedisClient.create("redis://" + url + ":" + port);
RedisHashCommands<String, String> redisCommands = redisClient.connect().sync();
List<String> fields = new LinkedList<>();

MapScanCursor<String, String> scanCursor = ?

do {
    scanCursor = redisCommands.hscan(key, scanCursor);
    fields.addAll(scanCursor.getMap().keySet());
} while (!scanCursor.isFinished());

How should I initialize "scanCursor"?

Upvotes: 0

Views: 1554

Answers (1)

mp911de
mp911de

Reputation: 18129

You have two options:

To answer your question, initialize scanCursor with just hscan(key).

MapScanCursor<String, String> scanCursor = null;

do {
    if (scanCursor == null) {
        scanCursor = redisCommands.hscan(key);
    } else {
        scanCursor = redisCommands.hscan(key, scanCursor);
    }
    fields.addAll(scanCursor.getMap().keySet());
} while (!scanCursor.isFinished());

Alternatively, you can use ScanIterator (see Lettuce 4.4) which is an Iterator and covers the complexity of Redis SCAN usage:

ScanIterator<KeyValue<String, String>> iterator = ScanIterator.hscan(redisCommands, key);

while (iterator.hasNext()) {

    KeyValue<String, String> next = iterator.next();
    // …
}

Update

Updated the do…while-based approach according to tcfritchman's comment.

Upvotes: 1

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