How do you handle cache expiration in Spring Boot?

Table of Contents

• Introduction
  • 1. Cache Expiration with TTL in Spring Boot
  • 2. Cache Expiration Using EhCache
    • Example: Setting Cache Expiration with EhCache
  • 3. Cache Expiration with Redis
    • Example: Setting Cache Expiration with Redis
  • 4. Cache Expiration Using Caffeine
    • Example: Setting Cache Expiration with Caffeine
  • 5. Manual Cache Eviction
    • Example: Using @CacheEvict for Cache Expiration
  • 6. Combining Cache Expiration with Cache Refresh
    • Example: Refreshing Cache After Expiration
• 7. Conclusion

Introduction

In Spring Boot applications, caching is a powerful mechanism to improve performance by storing method results in memory. However, one key challenge is ensuring that the cache does not serve stale or outdated data. Cache expiration, or time-to-live (TTL), is a technique used to automatically remove or refresh cached data after a certain period. This ensures that the cache remains consistent with the underlying data store.

Spring Boot provides several ways to handle cache expiration, including setting a TTL for cached data, manually evicting expired entries, and integrating with distributed caching systems like Redis. In this guide, we’ll explore various methods for managing cache expiration in Spring Boot.

1. Cache Expiration with TTL in Spring Boot

Spring Boot’s caching abstraction allows you to configure cache expiration through different caching providers. While Spring itself doesn't provide direct support for TTL, most caching solutions like EhCache, Redis, or Caffeine offer built-in support for cache expiration. These providers allow you to set the TTL for each cache entry, ensuring that expired data is automatically removed from the cache.

Let’s go over a few approaches to configure cache expiration in Spring Boot.

2. Cache Expiration Using EhCache

EhCache is a widely-used in-memory cache provider that integrates seamlessly with Spring Boot. To configure cache expiration with EhCache, you need to define the expiration policy in the ehcache.xml configuration file or programmatically.

Example: Setting Cache Expiration with EhCache

1. Add the EhCache dependency to **pom.xml**:

2. Configure EhCache in **ehcache.xml**:

3. Enable EhCache in your Spring Boot application:

In this example:

• We set the TTL of the cache to 10 seconds using the <ttl> tag in ehcache.xml.
• After 10 seconds, any cache entries in productsCache will automatically expire.

3. Cache Expiration with Redis

When using Redis as a cache provider, handling expiration is straightforward because Redis supports key expiration natively. You can configure TTL for cache entries either through Spring configuration or by setting a specific TTL in method-level annotations.

Example: Setting Cache Expiration with Redis

1. Add Redis dependencies to **pom.xml**:

2. Configure Redis Cache with TTL in **application.properties**:

This configuration will set a TTL of 10 seconds for all cache entries managed by Redis.

3. Use **@Cacheable** with Redis Cache Expiration:

In this example:

• The cache entries will expire automatically after the TTL (10 seconds).
• Redis takes care of evicting expired keys, so there is no need for manual cache removal.

4. Cache Expiration Using Caffeine

Caffeine is another popular caching provider that can be used with Spring Boot. It supports various expiration policies, including size-based eviction and time-based expiration (TTL).

Example: Setting Cache Expiration with Caffeine

1. Add Caffeine dependency to **pom.xml**:

2. Configure Cache Expiration with Caffeine in **CacheConfig.java**:

In this example:

• Caffeine is configured with a TTL of 10 seconds (expireAfterWrite).
• Cached entries will be evicted after 10 seconds of inactivity.

5. Manual Cache Eviction

In some cases, you might need more control over cache expiration and manually trigger cache eviction. Spring provides the @CacheEvict annotation to manually remove entries from the cache.

Example: Using @CacheEvict for Cache Expiration

In this example:

• Whenever a product is updated, the cache for that specific product is evicted using @CacheEvict.

6. Combining Cache Expiration with Cache Refresh

In some cases, you may want to refresh cached values when they expire. This can be achieved by combining cache expiration with cache refresh strategies using annotations like @Cacheable and @CachePut.

Example: Refreshing Cache After Expiration

In this setup:

• The @Cacheable annotation will automatically cache the result, and after it expires, the @CachePut annotation ensures the cache is updated with fresh data.

7. Conclusion

Handling cache expiration is crucial to maintaining cache consistency and ensuring that your application doesn't serve stale data. In Spring Boot, you can manage cache expiration in several ways, depending on the caching provider you're using (EhCache, Redis, Caffeine, etc.).

By configuring TTL, using manual eviction strategies, and leveraging the Spring Cache abstraction, you can ensure that your cache remains fresh, efficient, and aligned with your backend data. Proper cache expiration not only improves performance but also ensures that your application serves the most up-to-date information to users.