32. Caching
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32. Caching

The Spring Framework provides support for transparently adding caching to an application. At its core, the abstraction applies caching to methods, reducing thus the number of executions based on the information available in the cache. The caching logic is applied transparently, without any interference to the invoker.

[Note]Note

Check the relevant section of the Spring Framework reference for more details.

In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method:

import javax.cache.annotation.CacheResult;

import org.springframework.stereotype.Component;

@Component
public class MathService {

    @CacheResult
    public int computePiDecimal(int i) {
        // ...
    }

}
[Note]Note

You can either use the standard JSR-107 (JCache) annotations or Spring’s own caching annotations transparently. We strongly advise you however to not mix and match them.

[Tip]Tip

It is also possible to update or evict data from the cache transparently.

32.1 Supported cache providers

The cache abstraction does not provide an actual store and relies on abstraction materialized by the org.springframework.cache.Cache and org.springframework.cache.CacheManager interfaces. Spring Boot auto-configures a suitable CacheManager according to the implementation as long as the caching support is enabled via the @EnableCaching annotation.

[Tip]Tip

Use the spring-boot-starter-cache “Starter POM” to quickly add required caching dependencies. If you are adding dependencies manually you should note that certain implementations are only provided by the spring-context-support jar.

Spring Boot tries to detect the following providers (in this order):

It is also possible to force the cache provider to use via the spring.cache.type property.

If the CacheManager is auto-configured by Spring Boot, you can further tune its configuration before it is fully initialized by exposing a bean implementing the CacheManagerCustomizer interface. The following set the cache names to use.

@Bean
public CacheManagerCustomizer<ConcurrentMapCacheManager> cacheManagerCustomizer() {
    return new CacheManagerCustomizer<ConcurrentMapCacheManager>() {
        @Override
        public void customize(ConcurrentMapCacheManager cacheManager) {
            cacheManager.setCacheNames(Arrays.asList("one", "two"));
        }
    };
}
[Note]Note

=== In the example above, a ConcurrentMapCacheManager is expected to be configured. If that is not the case, the customizer won’t be invoked at all. You can have as many customizers as you want and you can also order them as usual using @Order or Ordered. ===

32.1.1 Generic

Generic caching is used if the context defines at least one org.springframework.cache.Cache bean, a CacheManager wrapping them is configured.

32.1.2 JCache

JCache is bootstrapped via the presence of a javax.cache.spi.CachingProvider on the classpath (i.e. a JSR-107 compliant caching library). It might happen than more that one provider is present, in which case the provider must be explicitly specified. Even if the JSR-107 standard does not enforce a standardized way to define the location of the configuration file, Spring Boot does its best to accommodate with implementation details.

# Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider
spring.cache.jcache.config=classpath:acme.xml
[Note]Note

Since a cache library may offer both a native implementation and JSR-107 support Spring Boot will prefer the JSR-107 support so that the same features are available if you switch to a different JSR-107 implementation.

There are several ways to customize the underlying javax.cache.cacheManager:

  • Caches can be created on startup via the spring.cache.cache-names property. If a custom javax.cache.configuration.Configuration bean is defined, it is used to customize them.
  • org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizer beans are invoked with the reference of the CacheManager for full customization.
[Tip]Tip

If a standard javax.cache.CacheManager bean is defined, it is wrapped automatically in a org.springframework.cache.CacheManager implementation that the abstraction expects. No further customization is applied on it.

32.1.3 EhCache 2.x

EhCache 2.x is used if a file named ehcache.xml can be found at the root of the classpath. If EhCache 2.x and such file is present it is used to bootstrap the cache manager. An alternate configuration file can be provide a well using:

spring.cache.ehcache.config=classpath:config/another-config.xml

32.1.4 Hazelcast

Spring Boot has a general support for Hazelcast. If a HazelcastInstance has been auto-configured, it is automatically wrapped in a CacheManager.

If for some reason you need a different HazelcastInstance for caching, you can request Spring Boot to create a separate one that will be only used by the CacheManager:

spring.cache.hazelcast.config=classpath:config/my-cache-hazelcast.xml
[Tip]Tip

If a separate HazelcastInstance is created that way, it is not registered in the application context.

32.1.5 Infinispan

Infinispan has no default configuration file location so it must be specified explicitly (or the default bootstrap is used).

spring.cache.infinispan.config=infinispan.xml

Caches can be created on startup via the spring.cache.cache-names property. If a custom ConfigurationBuilder bean is defined, it is used to customize them.

32.1.6 Redis

If Redis is available and configured, the RedisCacheManager is auto-configured. It is also possible to create additional caches on startup using the spring.cache.cache-names property.

32.1.7 Guava

If Guava is present, a GuavaCacheManager is auto-configured. Caches can be created on startup using the spring.cache.cache-names property and customized by one of the following (in this order):

  1. A cache spec defined by spring.cache.guava.spec
  2. A com.google.common.cache.CacheBuilderSpec bean is defined
  3. A com.google.common.cache.CacheBuilder bean is defined

For instance, the following configuration creates a foo and bar caches with a maximum size of 500 and a time to live of 10 minutes

spring.cache.cache-names=foo,bar
spring.cache.guava.spec=maximumSize=500,expireAfterAccess=600s

Besides, if a com.google.common.cache.CacheLoader bean is defined, it is automatically associated to the GuavaCacheManager.

32.1.8 Simple

If none of these options worked out, a simple implementation using ConcurrentHashMap as cache store is configured. This is the default if no caching library is present in your application.

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