SoFunction
Updated on 2025-04-14

Detailed explanation of precautions when setting cache keys when using Spring Cache

introduction

In modern web applications, caching is one of the important means to improve system performance and response speed. The Spring framework provides powerful caching support, and the caching function can be easily implemented through annotations such as @Cacheable, @CachePut, @CacheEvict. However, correctly setting the cache key is crucial to ensure the effectiveness and accuracy of the cache. This article will explore some precautions for setting cache keys when using Spring Cache.

1. Basic concepts of cache keys

In Spring Cache, the cache key is a string used to uniquely identify cache entries. When a method is called, Spring generates a unique key value based on the configured cache key and stores it in the cache with the method's return value. The next time the method is called and the same parameter is passed in, Spring will first check whether the corresponding key value exists in the cache. If it exists, it will directly obtain the results from the cache, avoiding repeated calculations.

2. Default cache key generator

If the cache key is not specified explicitly, Spring uses the default cache key generator​​SimpleKeyGenerator​​. The behavior of this generator is as follows:

  • If the method has no parameters, use​​​As a key.
  • If the method has only one parameter, the value of that parameter is used as the key.
  • If the method has multiple parameters, use​SimpleKey​​Object encapsulates all parameters.

This default behavior is sufficient in most cases, but may require custom cache keys in certain specific scenarios.

3. Custom cache key

3.1 Key attributes using @Cacheable annotation

Can be passed​@Cacheable​​Annotated​key​Properties to specify a custom cache key. For example:

@Cacheable(value = "books", key = "#isbn")
public Book findBook(String isbn) {
    // Method logic}

In this example,​#isbn​​Denote method parameters​isbn​The value of ​ will be used as the cache key.

3.2 Using SpEL expressions

Spring Cache supports the use of Spring Expression Language (SpEL) to generate more complex cache keys. For example:

@Cacheable(value = "users", key = "#username + '_' + #age")
public User getUser(String username, int age) {
    // Method logic}

In this example, the cache key is from​username​and​age​​A string spliced ​​by two parameters.

3.3 Using the KeyGenerator interface

If more flexible cache key generation strategy is required, it can be implemented​KeyGenerator​​Interface and register in Spring container. For example:

@Component
public class CustomKeyGenerator implements KeyGenerator {
    @Override
    public Object generate(Object target, Method method, Object... params) {
        StringBuilder sb = new StringBuilder();
        for (Object param : params) {
            (());
        }
        return ();
    }
}

Then specify the customization in the configuration file​KeyGenerator​​：

@Configuration
@EnableCaching
public class CacheConfig {
    @Autowired
    private CustomKeyGenerator customKeyGenerator;
 
    @Bean
    public CacheManager cacheManager() {
        SimpleCacheManager cacheManager = new SimpleCacheManager();
        ((
            new ConcurrentMapCache("books"),
            new ConcurrentMapCache("users")
        ));
        return cacheManager;
    }
 
    @Bean
    public KeyGenerator keyGenerator() {
        return customKeyGenerator;
    }
}

4. Things to note

4.1 Avoid using immutable objects as cache keys

If using immutable objects (such as​String​​) As a cache key, make sure that the values ​​of these objects do not change during cache. Otherwise, it may cause inconsistent cached data.

4.2 Consider the uniqueness and readability of cache keys

The cache key should be unique to ensure that different requests can be mapped to different cache entries correctly. At the same time, proper cache key naming can also help with debugging and maintenance.

4.3 Handling complex types of cache keys

If the method parameters are complex types (such as custom objects), make sure that these objects are implemented​equals​and​hashCode​​Methods so that the caching mechanism can correctly identify and compare them.

4.4 Consider the length of the cache key

Excessively long cache keys can cause performance issues, especially when using distributed caches. Try to keep the cache keys short and representative.

5. Summary

Properly setting the cache key is the key to ensuring the effectiveness of Spring Cache functionality. By rationally using the default cache key generator, custom cache keys, and paying attention to some common pitfalls, the performance and stability of the system can be significantly improved. I hope this article will be helpful to everyone using Spring Cache in actual development. This article introduces in detail the methods and precautions for setting cache keys in Spring Cache, hoping to help developers better understand and use Spring Cache functions. When using Spring Cache, it is very important to properly configure the cache key, which directly affects the cache hit rate and data consistency. Below I will explain how to set the cache key of Spring Cache through several practical application scenarios and provide corresponding sample code.

Scenario 1: Generate cache keys based on method parameters

Suppose there is a service method that querys the user's detailed information based on the user ID. We can generate cache keys based on user ID.

import ;
import ;
 
@Service
public class UserService {
 
    @Cacheable(value = "users", key = "#userId")
    public User getUserById(String userId) {
        // Simulate to obtain user information from the database        return (userId).orElse(null);
    }
}

In this example,​@Cacheable​​Annotated​key​​Properties specify usage method parameters​userId​​As a cache key.

Scenario 2: Generate compound cache keys based on multiple parameters

Suppose there is a service method that query order details based on the user ID and the order ID. We can generate a composite cache key based on these two parameters.

import ;
import ;
 
@Service
public class OrderService {
 
    @Cacheable(value = "orders", key = "#userId + '_' + #orderId")
    public Order getOrderDetails(String userId, String orderId) {
        // Simulate to get order details from the database        return (userId, orderId).orElse(null);
    }
}

In this example, the key attribute of the @Cacheable annotation specifies a string composed of userId and orderId as the cache key.

Scenario 3: Generate complex cache keys using SpEL expressions

Suppose there is a service method that queries the user's shopping cart information based on the user object. We can use SpEL expressions to generate cache keys.

import ;
import ;
 
@Service
public class ShoppingCartService {
 
    @Cacheable(value = "shoppingCarts", key = "# + '_' + #")
    public ShoppingCart getShoppingCart(User user) {
        // Simulate to obtain shopping cart information from the database        return (()).orElse(null);
    }
}

In this example,​@Cacheable​​Annotated​key​​Properties use SpEL expressions, specifying the user object.​id​and​email​​The string composed of attributes is used as a cache key.

Things to note

  1. Uniqueness of cache keys: Ensure that the generated cache key is unique in a specific cache area to avoid conflicts between different data.
  2. The simplicity of cache keys: Try to make the cache keys short and readable, making them easy to debug and maintain.
  3. Performance of cache keys: Avoid using overly complex SpEL expressions to generate cache keys to avoid affecting performance.
  4. Security of cache keys: If the cache key contains sensitive information (such as user ID), make sure that this information is not leaked in the log or monitoring.

Through the above examples and notes, I hope you can better understand and apply the cache key settings in Spring Cache. When using Spring Cache,​CacheKey​Generation of ​is a very important aspect, which determines the uniqueness of cached data. Spring Cache uses a simple one by default​KeyGenerator​to generate cache keys, but sometimes you need to customize this process to meet specific needs. Here are some things to do about how to set up and use​CacheKey​Notes, including related code examples:

1. Default Key Generator

Spring Cache is used by default​SimpleKeyGenerator​to generate cache keys. If the method has no parameters, it returns an empty​SimpleKey​Object; if the method has a parameter, it will use the parameter directly as the key; if there are multiple parameters, it will encapsulate these parameters into one​SimpleKey​Object.

public class SimpleKeyGenerator implements KeyGenerator {
    @Override
    public Object generate(Object target, Method method, Object... params) {
        if ( == 0) {
            return ;
        }
        if ( == 1) {
            Object param = params[0];
            if (param != null && !().isArray()) {
                return param;
            }
        }
        return new SimpleKey(params);
    }
}

2. Custom Key Generator

If you need more complex key generation logic, you can implement it​​KeyGenerator​​Interface custom key generator. For example, you might want to generate keys based on a combination of method names and parameter values.

import ;
import ;
 
public class CustomKeyGenerator implements KeyGenerator {
    @Override
    public Object generate(Object target, Method method, Object... params) {
        StringBuilder sb = new StringBuilder();
        (()).append(":");
        for (Object param : params) {
            (()).append(":");
        }
        return ();
    }
}

3. Use a custom Key generator in configuration

You can specify the use of custom ones in Spring's configuration file​KeyGenerator​​。

<beans xmlns="/schema/beans"
       xmlns:xsi="http:///2001/XMLSchema-instance"
       xmlns:cache="/schema/cache"
       xsi:schemaLocation="/schema/beans
           /schema/beans/
           /schema/cache
           /schema/cache/">
 
    <bean  class=""/>
 
    <cache:annotation-driven key-generator="customKeyGenerator"/>
</beans>

4. Specify keys using @Cacheable annotation

You can also​@Cacheable​​The key generation logic is directly specified in the annotation.

import ;
import ;
 
@Service
public class UserService {
 
    @Cacheable(value = "users", key = "#userId + '_' + #userName")
    public User getUser(String userId, String userName) {
        // Simulate to obtain user information from the database        return new User(userId, userName);
    }
}

In this example, the cache key will be from​userId​and​userName​​combination generation.

5. Things to note

  • Uniqueness of keys: Make sure the generated keys are unique and avoid cache conflicts.
  • Performance considerations: Complex key generation logic may affect performance, so try to keep the key generation logic simple and efficient.
  • Serialization: If using distributed caches (such as Redis), make sure that the generated keys can be correctly serialized and deserialized.
  • Security: Avoid including sensitive information such as user passwords in the keys.

Through the above introduction and examples, you can better understand and use the​​ in Spring Cache​CacheKey​​Settings to optimize your application performance.

The above is a detailed explanation of the precautions for setting cache keys when using Spring Cache. For more information about setting cache keys in Spring Cache, please pay attention to my other related articles!