Spring Cache

Spring Cache

Enable Cache

@Configuration
@EnableCaching
public class CachingConfig {

    @Bean
    public CacheManager cacheManager() {
        return new ConcurrentMapCacheManager("addresses");
    }
}

Using SpringBoot

When using Spring Boot, the mere presence of the starter package on the classpath alongside the EnableCaching annotation would register the same ConcurrentMapCacheManager. So there is no need for a separate bean declaration.

Use Caching With Annotations

@Cacheable

@Cacheable("addresses")
public String getAddress(Customer customer) {...}

The getAddress() call will first check the cache addresses before actually invoking the method and then caching the result.

• The default key is "", meaning all method parameters are considered as a key, unless a custom keyGenerator has been configured.

In this case, if any of the caches contain the required result, the result is returned and the method is not invoked.

@CacheEvict

We can use the @CacheEvict annotation to indicate the removal of one or more/all values so that fresh values can be loaded into the cache again:

@CacheEvict(value="addresses", allEntries=true)
public String getAddress(Customer customer) {...}

Here we’re using the additional parameter allEntries in conjunction with the cache to be emptied; this will clear all the entries in the cache addresses and prepare it for new data.

@CachePut

With the @CachePut annotation, we can update the content of the cache without interfering with the method execution. That is, the method will always be executed and the result cached:

@CachePut(value="addresses")
public String getAddress(Customer customer) {...}

The difference between @Cacheable and @CachePut is that @Cacheable will skip running the method, whereas @CachePut will actually run the method and then put its results in the cache.

@Caching

@Caching(evict = {
  @CacheEvict("addresses"),
  @CacheEvict(value="directory", key="#customer.name") })
public String getAddress(Customer customer) {...}

@CacheConfig

With the @CacheConfig annotation, we can streamline some of the cache configuration into a single place at the class level, so that we don’t have to declare things multiple times:

@CacheConfig(cacheNames={"addresses"})
public class CustomerDataService {

    @Cacheable
    public String getAddress(Customer customer) {...}

Conditional Caching

Conditional Parameter

@CachePut(value="addresses", condition="#customer.name=='Tom'")
public String getAddress(Customer customer) {...}

Unless Parameter

@CachePut(value="addresses", unless="#result.length()<64")
public String getAddress(Customer customer) {...}

Pitfalls

1. Not working while calling from another method of the same bean.

• https://stackoverflow.com/questions/12115996/spring-cache-cacheable-method-ignored-when-called-from-within-the-same-class
• https://spring.io/blog/2012/05/23/transactions-caching-and-aop-understanding-proxy-usage-in-spring
• https://stackoverflow.com/a/16899739/1501494
• https://stackoverflow.com/a/5251930/1501494

@Service
@Transactional(readOnly=true)
public class SettingServiceImpl implements SettingService {

@Inject
private SettingRepository settingRepository;

@Inject
private ApplicationContext applicationContext;

@Override
@Cacheable("settingsCache")
public String findValue(String name) {
    Setting setting = settingRepository.findOne(name);
    if(setting == null){
        return null;
    }
    return setting.getValue();
}

@Override
public Boolean findBoolean(String name) {
    String value = getSpringProxy().findValue(name);
    if (value == null) {
        return null;
    }
    return Boolean.valueOf(value);
}

/**
 * Use proxy to hit cache
 */
private SettingService getSpringProxy() {
    return applicationContext.getBean(SettingService.class); //通过这种方式获取bean
}