31. 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. Spring Boot auto-configures the cache infrastructure as long as the caching support is enabled via the @EnableCaching annotation.

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 org.springframework.cache.annotation.Cacheable
import org.springframework.stereotype.Component;

@Component
public class MathService {

    @Cacheable("piDecimals")
    public int computePiDecimal(int i) {
        // ...
    }

}

This example demonstrates the use of caching on a potentially costly operation. Before invoking computePiDecimal , the abstraction will look for an entry in the piDecimals cache matching the i argument. If an entry is found, the content in the cache is immediately returned to the caller and the method is not invoked. Otherwise, the method is invoked and the cache is updated before returning the value.

You can also use the standard JSR-107 (JCache) annotations (e.g. @CacheResult ) transparently. We strongly advise you however to not mix and match them.

If you do not add any specific cache library, Spring Boot will auto-configure a Simple provider that uses concurrent maps in memory. When a cache is required (i.e. piDecimals in the example above), this provider will create it on-the-fly for you. The simple provider is not really recommended for production usage, but it’s great for getting started and making sure that you understand the features. When you have made up your mind about the cache provider to use, please make sure to read its documentation to figure out how to configure the caches that your application uses. Practically all providers require you to explicitly configure every cache that you use in the application. Some offer a way to customize the default caches defined by the spring.cache.cache-names property.

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

If you are using the cache infrastructure with beans that are not interface-based, make sure to enable the proxyTargetClass attribute of @EnableCaching .

31.1 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.

If you haven’t defined a bean of type CacheManager or a CacheResolver named cacheResolver (see CachingConfigurer ), 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. Use this property if you need to disable caching altogether in certain environment (e.g. tests).

Use the spring-boot-starter-cache ‘Starter’ to quickly add basic caching dependencies. The starter brings in spring-context-support : if you are adding dependencies manually, you must include spring-context-support in order to use the JCache, EhCache 2.x or Guava support.

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 sets a flag to say that null values should be passed down to the underlying map.

@Bean
public CacheManagerCustomizer<ConcurrentMapCacheManager> cacheManagerCustomizer() {
    return new CacheManagerCustomizer<ConcurrentMapCacheManager>() {
        @Override
        public void customize(ConcurrentMapCacheManager cacheManager) {
            cacheManager.setAllowNullValues(false);
        }
    };
}

In the example above, an auto-configured ConcurrentMapCacheManager is expected. If that is not the case (either you provided your own config or a different cache provider was auto-configured), 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 .

31.1.1 Generic

Generic caching is used if the context defines at least one org.springframework.cache.Cache bean. A CacheManager wrapping all beans of that type is created.

31.1.2 JCache (JSR-107)

JCache is bootstrapped via the presence of a javax.cache.spi.CachingProvider on the classpath (i.e. a JSR-107 compliant caching library) and the JCacheCacheManager provided by the spring-boot-starter-cache ‘Starter’. There are various compliant libraries out there and Spring Boot provides dependency management for Ehcache 3, Hazelcast and Infinispan. Any other compliant library can be added as well.

It might happen that more than 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

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.

Spring Boot has a general support for Hazelcast. If a single HazelcastInstance is available, it is automatically reused for the CacheManager as well unless the spring.cache.jcache.config property is specified.

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.

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.

31.1.3 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, the EhCacheCacheManager provided by the spring-boot-starter-cache ‘Starter’ and such file is present it is used to bootstrap the cache manager. An alternate configuration file can be provided as well using:

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

31.1.4 Hazelcast

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

31.1.5 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.

The support of Infinispan in Spring Boot is restricted to the embedded mode and is quite basic. If you want more options you should use the official Infinispan Spring Boot starter instead, check the documentation for more details.

31.1.6 Couchbase

If the Couchbase java client and the couchbase-spring-cache implementation are available and Couchbase is configured, a CouchbaseCacheManager will be auto-configured. It is also possible to create additional caches on startup using the spring.cache.cache-names property. These will operate on the Bucket that was auto-configured. You can also create additional caches on another Bucket using the customizer: assume you need two caches on the "main" Bucket ( foo and bar ) and one biz cache with a custom time to live of 2sec on the another Bucket . First, you can create the two first caches simply via configuration:

spring.cache.cache-names=foo,bar

Then define this extra @Configuration to configure the extra Bucket and the biz cache:

@Configuration
public class CouchbaseCacheConfiguration {

    private final Cluster cluster;

    public CouchbaseCacheConfiguration(Cluster cluster) {
        this.cluster = cluster;
    }

    @Bean
    public Bucket anotherBucket() {
        return this.cluster.openBucket("another", "secret");
    }

    @Bean
    public CacheManagerCustomizer<CouchbaseCacheManager> cacheManagerCustomizer() {
        return c -> {
            c.prepareCache("biz", CacheBuilder.newInstance(anotherBucket())
                    .withExpiration(2));
        };
    }

}

This sample configuration reuses the Cluster that was created via auto-configuration.

31.1.7 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.

By default, a key prefix is added to prevent that if two separate caches use the same key, Redis would have overlapping keys and be likely to return invalid values. We strongly recommend to keep this setting enabled if you create your own RedisCacheManager .

31.1.8 Caffeine

Caffeine is a Java 8 rewrite of Guava’s cache and will supersede the Guava support in Spring Boot 2.0. If Caffeine is present, a CaffeineCacheManager (provided by the spring-boot-starter-cache ‘Starter’) 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):

  • A cache spec defined by spring.cache.caffeine.spec

  • A com.github.benmanes.caffeine.cache.CaffeineSpec bean is defined

  • A com.github.benmanes.caffeine.cache.Caffeine 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.caffeine.spec=maximumSize=500,expireAfterAccess=600s

Besides, if a com.github.benmanes.caffeine.cache.CacheLoader bean is defined, it is automatically associated to the CaffeineCacheManager . Since the CacheLoader is going to be associated to all caches managed by the cache manager, it must be defined as CacheLoader<Object, Object> . Any other generic type will be ignored by the auto-configuration.

31.1.9 Guava (deprecated)

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):

  • A cache spec defined by spring.cache.guava.spec

  • A com.google.common.cache.CacheBuilderSpec bean is defined

  • 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 . Since the CacheLoader is going to be associated to all caches managed by the cache manager, it must be defined as CacheLoader<Object, Object> . Any other generic type will be ignored by the auto-configuration.

31.1.10 Simple

If none of the other providers can be found, a simple implementation using a ConcurrentHashMap as cache store is configured. This is the default if no caching library is present in your application. Caches are created on-the-fly by default but you can restrict the list of available caches using the cache-names property. For instance, if you want only foo and bar caches:

spring.cache.cache-names=foo,bar

If you do this and your application uses a cache not listed then it will fail at runtime when the cache is needed, but not on startup. This is similar to the way the "real" cache providers behave if you use an undeclared cache.

31.1.11 None

When @EnableCaching is present in your configuration, a suitable cache configuration is expected as well. If you need to disable caching altogether in certain environments, force the cache type to none to use a no-op implementation:

spring.cache.type=none
Updated at: 7 months ago
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