Retrieve existing key-value pair present in Redis using Redisson

Question

I want to fetch existing key value pair from redis using redisson. The issue is that I did not enter that key value pair through redisson, and I am not able to find any function from documentation to fetch existing key and value present as a string.

Answer 1

We can get all existing key from redis cache by using redisson client in the following way..

1.Add mvn dependency in your project pom.xml.

            <dependency>
                <groupId>org.redisson</groupId>
                <artifactId>redisson</artifactId>
                <version>3.16.3</version>
            </dependency>
    

Now create RedisConfig class to create connection with redis server by using redisson client

public class RedisConfig{
            private static final Logger logger  = LoggerFactory.getLogger(RedisConfig.class);
            @Autowired
            CacheManager cacheManager;
            @Value("${spring.redis.port}")
            private String redisPort;
            @Value("${spring.redis.host}")
            private String redisHost;
            @Value("${spring.redis.password}")
            private String password;
        
            @Bean
            public RedissonClient getRedissonClient() {
                    Config config = new Config();
                    String address="redis://"+redisHost+":"+redisPort;
                    config.useSingleServer().setAddress(address)
                            .setPassword(password);
                    RedissonClient client = Redisson.create(config);
                    return client;
            }
        }
        

Now suppose you want to access all the keys of your cache(By CacheName) then create another function

public Iterator<String>getKeysByCacheName(String cacheName){
                RedissonClient client = getRedissonClient();
                RKeys keys = client.getKeys();
                Iterator<String> allKeys = keys.getKeysByPattern(cacheName+"*").iterator();
                return allKeys;
            }
    

Here * is access all the keys. Now use the below code to get all keys with there values.

Iterator<String> allKeys = redisConfig.getKeysByCacheName("CacheName");
                    while (allKeys.hasNext()) {
                        String key = allKeys.next().split("::")[1];
                        Student student = (Student ) cacheManager.getCache("CacheName").get(key).get();
                        if (student !=null)
                            System.out.println("Cached Student Object is "+student );
}

Similarly to set/add cache you can use

cacheManager.getCache("CacheName").put("Key",Student);