Redis as cache provider in Spring Boot

Introduction

Redis helps your Spring Boot app remember data quickly. It stores data in memory so your app can get it fast without waiting for slow databases.

You want to speed up repeated data requests in your app.

You need to reduce load on your main database by caching results.

You want to store session data or user preferences temporarily.

You want to share cached data between multiple app instances.

You want a simple way to improve app performance with minimal code changes.

Syntax

Spring Boot

spring.cache.type=redis
spring.redis.host=localhost
spring.redis.port=6379

@EnableCaching
@Configuration
public class CacheConfig {

  @Bean
  public RedisCacheManager cacheManager(RedisConnectionFactory factory) {
    return RedisCacheManager.builder(factory).build();
  }
}

Set Redis connection details in application.properties or application.yml.

Use @EnableCaching to activate caching in Spring Boot.

Examples

This caches the result of getBookById in Redis under the 'books' cache.

Spring Boot

@Cacheable("books")
public Book getBookById(Long id) {
  // method logic
}

This removes a specific book from the Redis cache when called.

Spring Boot

@CacheEvict(value = "books", key = "#id")
public void removeBookFromCache(Long id) {
  // method logic
}

This updates the cached book data after modifying it.

Spring Boot

@CachePut(value = "books", key = "#book.id")
public Book updateBook(Book book) {
  // method logic
  return book;
}

Sample Program

This Spring Boot app uses Redis to cache book titles. The first call to getBookTitleById waits 3 seconds, but later calls return instantly from cache.

Spring Boot

package com.example.cache;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.stereotype.Service;

@SpringBootApplication
@EnableCaching
public class CacheApplication {

  public static void main(String[] args) {
    SpringApplication.run(CacheApplication.class, args);
  }

  @Configuration
  static class CacheConfig {
    @Bean
    public RedisCacheManager cacheManager(RedisConnectionFactory factory) {
      return RedisCacheManager.builder(factory).build();
    }
  }

  @Bean
  public CommandLineRunner demo(BookService bookService) {
    return args -> {
      System.out.println("Calling getBookTitleById(1) first time...");
      String result1 = bookService.getBookTitleById(1L);
      System.out.println("Result: " + result1);
      System.out.println("Calling getBookTitleById(1) second time...");
      String result2 = bookService.getBookTitleById(1L);
      System.out.println("Result: " + result2);
    };
  }

  @Service
  static class BookService {

    @Cacheable("books")
    public String getBookTitleById(Long id) {
      simulateSlowService();
      return "Book Title " + id;
    }

    private void simulateSlowService() {
      try {
        Thread.sleep(3000); // simulate delay
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
      }
    }
  }
}

Important Notes

Make sure Redis server is running locally or update host/port accordingly.

Cached data stays in Redis until expired or evicted.

Use @Cacheable on methods that return data you want to cache.

Summary

Redis stores data in memory for fast access in Spring Boot apps.

Use @EnableCaching and RedisCacheManager to enable Redis caching.

Annotate methods with @Cacheable to cache their results automatically.