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Spring Cache Redis Implementation

Working example to show Spring Boot Cache integration with Redis using Redisson client.

  • Redis is an in-memory data structure store implementing a distributed, in-memory key-value database with optional durability. It can be used as a database, cache or as a message broker.

  • Redisson is a Redis client for Java. Redisson constitutes an in-memory data grid that offers distributed Java objects and services backed by Redis. It's distributed in-memory data model allows sharing of domain objects and services across applications and servers.

Spring Boot Redis Cache Maven Configuration

We can use spring-boot-starter-data-redis maven artifact provided by Spring boot to integrate Redis with spring boot project.

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

In order to use Redisson client, we have to include below dependencies.

<dependency>
	<groupId>org.redisson</groupId>
	<artifactId>redisson-spring-boot-starter</artifactId>
	<version>3.12.4</version>
</dependency>

Spring Boot Redis Configuration

Redisson supports both Spring Cache and JCache implementation. Example for both implementation has been provided below.

spring.cache.type property defines the type of implementation to load.

  • spring.cache.type=redis - Loads Spring Cache implementation. (Default)
  • spring.cache.type=jcache - Loads JCache implementation.

Implementation

Spring Implementation

Redisson provides Redis based Spring Cache implementation made according to Spring Cache specification. Each Cache instance has two important parameters: ttl and maxIdleTime and stores data infinitely if they are not defined or equal to 0.

Set below property to load this config.
spring.cache.type=redis

RedisCacheConfig provides the configuration for beans required for cache.

  • Creates RedissonClient after reading redis-<profile>.yml file.
    @Bean(destroyMethod = "shutdown")
    public RedissonClient redissonClient() throws IOException {
    	String configFileName = "redis-" + activeProfile + ".yml";
    	File resourceURL = ResourceUtils.getFile("classpath:" + configFileName);
    	Config config = Config.fromYAML(resourceURL);
    	redisson = Redisson.create(config);
    	return redisson;
    }
  • Loads cache config and creates CacheManager from cache-config-<activeProfile>.yml file.
    @Bean
    public CacheManager cacheManager(RedissonClient redissonClient) throws IOException {
    	String configFileName = "cache-config-" + activeProfile + ".yml";
    	return new RedissonSpringCacheManager(redissonClient, "classpath:/" + configFileName);
    }
JCache API (JSR-107) implementation

Redisson provides an implementation of JCache API (JSR-107) for Redis.

Set below property to load this config.
spring.cache.type=jcache

RedisJCacheConfig provides the configuration for beans required for cache.

  • RedissonClient remains same as above implementation.
  • In order to define different cache and ttl we have to add them to application.yml file under application.cache key.

Sample yml files are available in the resources folder.

@EnableCaching in Spring Boot

The @EnableCaching annotation triggers a post-processor that inspects every Spring bean for the presence of caching annotations on public methods. If such an annotation is found, a proxy is automatically created to intercept the method call and handle the caching behavior accordingly. The post-processor handles the @Cacheable, @CachePut and @CacheEvict annotations. CacheConfig - Config class to enable caching. (annotated with @EnableCaching to enable caching)

To handle all type of exceptions while caching, we can define an implementation of CacheErrorHandler. In current example, we have defined AppCacheErrorHandler which just logs the exception while caching and continue the processing. Typically, failing to retrieve an object from the cache with a given id can be managed as a cache miss by not throwing back such exception.

@Cacheable annotation

The @Cacheable annotation can be applied at method level. When applied at method level, then the annotated method’s return value is cached with key as the method parameter. You can use other params such as cacheName, cacheManager, conditions with it.

Below code cache the response of method findUserById to usersCache as per ttl defined in properties file. Also, unless property makes sure that null response is not cached.

@Cacheable(value = "usersCache", key="#id",  unless = "#result == null")
public User findUserById(Long id) {
	LOGGER.info("Getting user with id {}", id);
	return userRepository.findById(id).orElse(null);
}
@CachePut - Updating Cache

Cache values should also update whenever their actual objects value are updated. This can be done using @CachePut annotation:

@CachePut(value = "usersCache", key = "#user.id")
public User updateUser(User user) {
    LOGGER.info("Updating user with ID {}", user.getId());
    return userRepository.save(user);
}
@CacheEvict - Deleting Cache
@CacheEvict(value = "usersCache", key = "#id")
public void deleteUser(Long id) {
	LOGGER.info("Deleting user with id {}", id);
	userRepository.deleteById(id);
}

Build JAR

  1. Change to project directory and open command line.
  2. Run below command. This will generate jar file in target folder.
    mvn clean install
  3. Execute below command to run the jar java -jar -Dspring.profiles.active=dev target/spring-cache-1.0.0.jar

Test Application

curl http://localhost:8080/user/1

Hit the above url twice and check in IDE console, method invocation should happen only once.

Also, you validate redis by login to redis-cli and running command keys *usersCache*