Redis Notifications in Java

What are Redis Notifications?

Redis is an open source, in-memory data structure store that can implement NoSQL databases, caches, and message brokers. Redis is used for many different high-performance, mission-critical applications, which means availability, security, and observability are crucial.

In support of these goals, Redis provides notifications to inform users about specific events that occur within a Redis server. Notifications provide real-time alerts that something unusual has happened within a Redis database. For example, an important entry may have been modified due to a security breach or developer error.

Users can subscribe to a pub/sub channel to receive events that affect their Redis client. For example, you can be notified when keys are created, deleted, expired, or evicted (removed for memory reasons). These are known as keyspace notifications. Redis notifications can also assist with monitoring and logging, such as by sending alerts when clients disconnect or when a server configuration changes.

How to Activate Redis Notifications

Before you can use Redis notifications, they need to be activated using the notify-keyspace-events setting in your Redis configuration file (usually called redis.conf).

For example, you can enable Redis keyspace notifications from the Redis command line using the following command:

redis-cli config set notify-keyspace-events KEA

Here, KEA indicates you want to receive all Redis keyspace notifications. You can also alter this command to receive specific types of notifications. For example, KElhe indicates that you only want to receive keyspace notifications about list commands (e.g., adding or removing elements from a list), hash commands (e.g., modifying the value of a hash), and expired keys.

How to Get Redis Notifications in Java

Redis has a wide range of use cases, but it also comes with a number of caveats that you should be aware of. For example, the base version of Redis isn't compatible with the Java programming language. Instead, Java developers who want to use Redis with Java can use a third-party Redis Java framework, such as Redisson.

Redisson is a Redis Java client that dramatically lowers the learning curve for Java developers using Redis. The Redisson library comes with implementations of many familiar Java data structures, services, and components, helping Java developers get started with Redis right away. For example, Redisson includes data structures such as RList, RSet, RMap, and RBinaryStream that implement these Java constructs in Redis.

To get Redis notifications in Java, Redisson allows you to bind listeners to these objects. For example, developers can bind a ListAddListener to an RList object, receiving a notification when a new element is added to the list. Below is a code snippet that illustrates how to bind different types of listeners to an RMap object. These listeners will be notified when the object is deleted or expired, respectively:

RMap map = redisson.getMap("anyMap");

int listenerId = map.addListener(new DeletedObjectListener() {
    public void onDeleted(String name) {
         // ...

int listenerId = map.addListener(new ExpiredObjectListener() {
    public void onExpired(String name) {
         // ...

Listeners can also be removed from an object as follows:


To learn more about how to receive Redis notifications in Java or for more advantages of the Redisson library, check out the Redisson documentation.

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