1. Introduction

The @CachePut annotation in Spring Framework is used to update the cache without interfering with the method execution. Unlike @Cacheable, which may skip the method execution if the value is already in the cache, @CachePut always executes the method and updates the cache with the result.

2. Use Case

Use @CachePut when:

• You want the method to execute every time (e.g., an update operation).
• You want to update the cache with the method result.

3. Syntax

@CachePut(cacheNames = "cacheName", key = "#id")
public ReturnType methodName(Type id) {
    // logic that updates data
    return updatedValue;
}

4. How It Works

• The method will execute regardless of the cache state.
• The result of the method execution will be placed into the cache.
• Subsequent reads using @Cacheable with the same key can benefit from the updated cache.

5. Example

1. Setup cache in Spring Boot application

Setup cache in Spring Boot application

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

2. Create a service using @CachePut

@Service
public class ProductService {

    private final Map<Long, Product> database = new ConcurrentHashMap<>();

    public ProductService() {
        database.put(1L, new Product(1L, "iPhone", 75000));
    }

    @Cacheable(value = "products", key = "#id")
    public Product getProductById(Long id) {
        System.out.println("Fetching from DB for id: " + id);
        return database.get(id);
    }

    @CachePut(value = "products", key = "#product.id")
    public Product updateProduct(Product product) {
        System.out.println("Updating product in DB and cache: " + product);
        database.put(product.getId(), product);
        return product;
    }
}

3. Sample Controller

@RestController
@RequestMapping("/products")
public class ProductController {

    @Autowired
    private ProductService productService;

    @GetMapping("/{id}")
    public Product getProduct(@PathVariable Long id) {
        return productService.getProductById(id);
    }

    @PutMapping
    public Product updateProduct(@RequestBody Product product) {
        return productService.updateProduct(product);
    }
}

4. Output Behavior

• First call to GET /products/1 → Hits DB and caches result.
• Second call to GET /products/1 → Returns from cache.
• Call PUT /products with updated product → Updates DB and also updates the cache due to @CachePut.
• Next call to GET /products/1 → Returns updated value from the cache.

5. Difference Between @CachePut, @Cacheable, and @CacheEvict

Annotation	Executes Method?	Reads from Cache?	Updates Cache?	When to Use?
@Cacheable	No (if cached)	Yes	No	For reads, to avoid recomputation.
@CachePut	Always	No	Yes	For writes/updates.
@CacheEvict	Optional	No	No (removes)	For deletions, to clear cache.