Redis Cache in Java (with Spring Boot)

Redis is a high-performance, in-memory key-value store often used for caching in Java applications. When integrated with Spring Boot, it becomes very easy to use with annotations like @Cacheable, @CachePut, and @CacheEvict.

🔧 Step-by-Step: Using Redis Cache in Java (Spring Boot)

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✅ 1. Add Maven Dependency (spring-boot-starter-data-redis)

xml
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

You may also need:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>

And for embedded Redis during testing (optional):

xml
<dependency>
    <groupId>it.ozimov</groupId>
    <artifactId>embedded-redis</artifactId>
    <version>0.7.2</version>
</dependency>

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✅ 2. Enable Caching in Main Class

@SpringBootApplication
@EnableCaching
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

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✅ 3. Configure Redis in application.properties

properties

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

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✅ 4. Example Entity and Repository

Entity (e.g., Department.java):

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Department implements Serializable {
    private Long id;
    private String name;
    private String code;
}

Repository:

@Repository
public class DepartmentRepository {

    private Map<Long, Department> departmentMap = new HashMap<>();

    public Department findById(Long id) {
        simulateSlowService();
        return departmentMap.get(id);
    }

    private void simulateSlowService() {
        try {
            Thread.sleep(3000); // simulate DB call
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

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✅ 5. Cache Logic with @Cacheable

@Service
public class DepartmentService {

    @Autowired
    private DepartmentRepository repository;

    @Cacheable(value = "departments", key = "#id")
    public Department getDepartmentById(Long id) {
        return repository.findById(id);
    }

    @CacheEvict(value = "departments", key = "#id")
    public void deleteDepartment(Long id) {
        // deletion logic here
    }

    @CachePut(value = "departments", key = "#department.id")
    public Department updateDepartment(Department department) {
        // update logic here
        return department;
    }
}

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✅ 6. Redis Console

Make sure Redis is running:

bash

redis-server

You can view keys via:

bash

redis-cli
127.0.0.1:6379> KEYS *

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✅ Sample Behavior

1. First call to getDepartmentById(1) → takes 3 seconds (simulated)

2. Next call → instant (from Redis cache)

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✅ Summary

Annotation	Purpose
@Cacheable	Caches the result of a method call
@CachePut	Updates the cache after method call
@CacheEvict	Removes entry from cache
@EnableCaching	Enables Spring’s cache abstraction