Connect to Redis
Overview
Caching is a common technique to improve the performance of any application. Frequently accessed data can be cached, so avoid repeated, expensive database/third-party service calls. Varieties of caching solutions are available in the market, and Redis is one of them and a popular one.
What Is Redis?
The official definition of Redis from its website
Redis is an open-source, in-memory data store used by millions of developers as a database, cache, streaming engine, and message broker.
Let's understand each capability.
- In-memory data store - By default, Redis keeps data in memory through key-value pairs.
- Database - Redis can be used as a persistence database. By default, Redis keep information in memory; however, it can also be configured to store the information in the physical disk.
- Caching - This capability of Redis is used widely. Its primary intent was to use it as a highly available distributed cache.
- Streaming engine - The stream data type enables high-rate data ingestion, messaging, event sourcing, and notifications.
- Message broker - Redis can be used as a message broker to implement the pub-sub architecture.
Redis has many capabilities but it is traditionally used as cache.
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Spring Boot Redis Project Setup
Spring boot offers simple integration with Redis using starters and application.properties configuration. It also offers a RedisRepository just like JpaRepository to perform operations on the Redis store.
Dependencies
We need two dependencies to work with Redis.
- Spring Redis abstraction
- Java client for Redis
Alternatively, you can use starter dependency will bring jedis along with it.
The above starter dependency comes with a default configuration which can be overridden using the application.properties configuration.
Configuring Redis
By default, Redis runs on your system on host localhost and port 6379. The starter-data-redis comes with the same default configuration; therefore, no need for extra configuration.
If you use a configuration other than the default, it can be provided using properties spring.redis.*. For example, if your Redis instance runs on port 6000, you need to specify a port in the application configuration.
Defining the Model
Let's use an Intern entity and perform operations on it.
Note - The annotation on top is @RedisHash, which marks Objects as aggregate roots to be stored in a Redis.
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Defining the Repository
To interact with Redis and the Intern entity, we have a repository not different from regular CrudRepository. Behind the scene, spring takes care of where to fetch information from.
CrudRepository comes with a basic CRUD method, as the name suggests. Now we can perform different operations on the Redis.
Creating a new Redis cache entry
InternRepository#save method will create a new entry in the Redis store.
Updating the existing Cache entry
No special methods are available to update the cache entry. InternRepository#save will update the entry if it already exists in the Redis store.
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Clearing Cache
To delete entries from the Redis store, use the method InternReposotory#deleteById.
Conclusion
- Redis is a key-value database used widely across the industry.
- Redis can be used as a cache, database, pub-sub, and streaming engine.
- Spring boot offers spring-boot-starter-data-redis dependency to simplify integration.
- Redis model uses @RedisHash annotation to mark as a Redis entity.
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