What is the @CachePut annotation in Spring Boot, its principle, and how to use it
Introduction
In Spring Boot, the @CachePut annotation is one of the annotations for caching and is used to update data in the cache. Compared with the @Cacheable annotation, the @CachePut annotation can be used to update the data in the cache, not just read the data in the cache. In this article, we will introduce the role, principle and how to use the @CachePut annotation.
The role of @CachePut annotation
The @CachePut annotation is one of the annotations used to update the cache in Spring Boot. When using the @CachePut annotation, you need to place the annotation on the method that needs to update the cache. This annotation will tell Spring Boot to update the return value of the method to the cache after the method is executed.
In Spring Boot, the @CachePut annotation is used to update the data in the cache. When the method is called, Spring Boot will first check if the data already exists in the cache. If the data exists in the cache, the data in the cache will be updated as the return value of the method; if the data does not exist in the cache, the return value of the method will be added to the cache.
Principle of @CachePut annotation
In Spring Boot, the @CachePut annotation is implemented through the AOP (aspect-oriented programming) mechanism. Specifically, the @CachePut annotation is implemented through Spring Boot's cache interceptor. When the annotated method is called, Spring Boot's cache interceptor will intercept the method and update the cache according to the properties specified in the annotation.
When updating the cache, Spring Boot will first look up whether the data already exists in the cache based on the cache name and cache key. If the data already exists in the cache, the data in the cache will be updated as the return value of the method; if the data does not exist in the cache, the return value of the method will be added to the cache.
It should be noted that the @CachePut annotation does not affect the execution of the method. Even if the update of the cache fails, the method will execute normally. Therefore, when using the @CachePut annotation, it is necessary to ensure that the execution result of the method is consistent with the update result of the cache.
How to use @CachePut annotation
In Spring Boot, using the @CachePut annotation is very simple. You only need to add the @CachePut annotation to the method that needs to update the cache, and the method can be included in the scope of cache management. Here is an example using the @CachePut annotation:
@Service
public class UserService {
@Autowired
private UserRepository userRepository;
@CachePut(value = "userCache", key = "#user.id")
public User saveUser(User user) {
return userRepository.save(user);
}
}
In the above example, the saveUser() method is annotated with @CachePut and specifies the cache name and cache key. When this method is called, Spring Boot will update the return value of the method to the cache, the cache name is userCache, and the cache key is user.id.
It should be noted that the @CachePut annotation must specify the cache name and cache key. If no cache name and cache key are specified, Spring Boot will not be able to determine which cache to update.
In addition to using the @CachePut annotation on the method, you can also use the @CachePut annotation on the class to include all methods in the class within the scope of cache management. Below is an example:
@Service
@CachePut(value = "userCache", keyGenerator = "myKeyGenerator")
public class UserService {
@Autowired
private UserRepository userRepository;
public User saveUser(User user) {
return userRepository.save(user);
}
public User getUserById(Long userId) {
return userRepository.findById(userId).orElse(null);
}
}
In the above example, the UserService class is marked with @CachePut annotation and specifies the cache name and key generator. All methods in this class will therefore be scoped to cache management and use the specified cache name and key generator.
In addition to specifying the cache name and cache key, the @CachePut annotation also supports other attributes, such as conditional expressions, cache managers, etc. Here is an example of @CachePut annotation with attributes:
@Service
public class UserService {
@Autowired
private UserRepository userRepository;
@CachePut(value = "userCache", key = "#user.id", condition = "#user.age > 18")
public User saveUser(User user) {
return userRepository.save(user);
}
}
In the above example, the @CachePut annotation also specifies a conditional expression, that is, only when user.age is greater than 18, the return value of the method will be updated to the cache.
Summarize
The @CachePut annotation is one of the annotations used to update the cache in Spring Boot, and is used to update the return value of the method into the cache. Compared with the @Cacheable annotation, the @CachePut annotation can be used to update the data in the cache, not just read the data in the cache. In this article, we introduced the role, principle and how to use the @CachePut annotation. In actual development, reasonable use of the @CachePut annotation can improve the readability and maintainability of the code, as well as improve the performance and stability of the system.