Add caching example with Spring Data Redis #256
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Summary of Changes
Hello @rashidi, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request introduces a new, self-contained example project that illustrates the integration of Spring Data Redis for caching within a Spring Boot application. It provides a practical demonstration of configuring Redis as a cache manager and leveraging Spring's @Cacheable annotation on Spring Data JPA repositories, complete with robust testing using Testcontainers.
Highlights
- New Example Module: I've added a new Gradle module named
data-redis-cacheto demonstrate how to implement caching using Spring Data Redis with Spring Boot and Spring Data JPA. - Caching Configuration: The new module includes a
CacheConfigurationclass that enables Spring's caching mechanism and configuresRedisCacheManagerto use Redis as the caching store. - Cacheable Repository Methods: I've applied
@Cacheableannotations tofindAll()andfindById()methods within theCustomerRepositoryto showcase how Spring automatically caches method results, improving performance for repeated queries. - Testcontainers Integration: The example includes comprehensive integration tests using Testcontainers for both PostgreSQL (for the JPA entity) and Redis, ensuring the caching setup works as expected in a realistic environment.
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Code Review
The code changes introduce a new module demonstrating caching with Spring Data Redis. The review includes fixes for the Customer entity's equals and hashCode methods to prevent NullPointerExceptions and ensure correctness with collections. Improvements to the test implementation for better robustness and maintainability have also been suggested.
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| @Override | ||
| public final boolean equals(Object o) { | ||
| return o instanceof Customer another && this.id.equals(another.id); |
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This implementation will throw a NullPointerException if this.id is null, which is the case for a new entity before it's persisted. You should add a null-check for the id before calling .equals() on it to prevent this.
| return o instanceof Customer another && this.id.equals(another.id); | |
| return o instanceof Customer another && id != null && id.equals(another.id); |
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| @Override | ||
| public int hashCode() { | ||
| return id.hashCode(); |
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This hashCode implementation will throw a NullPointerException if id is null. Furthermore, for JPA entities with generated IDs, the hash code will change after the entity is persisted. This can cause issues if the entity is stored in a HashSet or as a key in a HashMap.
A common and safer practice is to use a constant hash code that doesn't depend on the generated ID, ensuring the hash code is stable throughout the entity's lifecycle.
| return id.hashCode(); | |
| return getClass().hashCode(); |
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| @Bean | ||
| public RedisCacheManager cacheManager(RedisConnectionFactory connectionFactory) { | ||
| return RedisCacheManager.create(connectionFactory); |
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The RedisCacheManager.create() method has been deprecated since Spring Framework 6.1. It's recommended to use the builder pattern, which provides more flexibility for configuration.
| return RedisCacheManager.create(connectionFactory); | |
| return RedisCacheManager.builder(connectionFactory).build(); |
| @DisplayName("Given the method name is configured as the cache's key Then subsequent retrieval should return the same value as initial retrieval") | ||
| void findAll() { | ||
| var persisted = customers.findAll(); | ||
| var cached = caches.getCache("customers").get("findAll").get(); |
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Directly chaining .get() can lead to a NullPointerException if the cache entry for the key "findAll" does not exist, as caches.getCache("customers").get("findAll") would return null. This can make test failures harder to diagnose.
A more robust approach would be to verify the ValueWrapper is not null before getting its value.
| @DisplayName("Given the cache is configured Then subsequent retrieval with the same key should return the same value as initial retrieval") | ||
| void findById() { | ||
| var persisted = customers.findById(1L).get(); | ||
| var cached = caches.getCache("customerById").get(1L).get(); |
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Directly chaining .get() can lead to a NullPointerException if the cache entry for the key 1L does not exist, as caches.getCache("customerById").get(1L) would return null. This can make test failures harder to diagnose.
A more robust approach would be to verify the ValueWrapper is not null before getting its value.
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