Spring Cache @Cacheable Method Ignored When Called from Within The Same Class

因工作需要使用 Spring Cache 整合 EhCache 時, 意外發現標注 @Cacheable annotation 的 method 在 same class 呼叫發揮不了效用

以下為範例 code：

@Cacheable(value = CacheConstants.FIND_ALL_TYPE)
@Override
public List<Type> getList() {
    return super.getList();
}
    
public List<Type> getListByOrgMappingAndStatusOrderBySortAsc(OrgMapping orgMapping, Activation status) {
    return getList().stream()
            .filter(type -> type.getOrgMapping().equals(orgMapping))
            .filter(type -> type.getStatus().equals(Activation.ACTIVE))
            .sorted((t1, t2) -> t1.getSort().compareTo(t2.getSort()))
            .collect(Collectors.toList());
}<span data-mce-type="bookmark" style="display: inline-block; width: 0px; overflow: hidden; line-height: 0;" class="mce_SELRES_start"></span>

折騰了很久，也發現到網路很多類似的問題：

Spring cache @Cacheable method ignored when called from within the same class
Spring Cache @Cacheable – not working while calling from another method of the same bean
@Cacheable method ignored when called from within the same class

其中讓我看到了一段文字恍然大悟！！！

Only external method calls coming in through the proxy are intercepted. This means that self-invocation, in effect, a method within the target object calling another method of the target object, will not lead to an actual cache interception at runtime even if the invoked method is marked with @Cacheable.
Wiki: Using Cacheable

原來 same class 不會觸發 Spring AOP 代理機制，必須用 AspectJ 取代 Spring AOP，以下為解決方式：

public List<Type> getListByOrgMappingOrderBySortAsc(OrgMapping orgMapping) {
    return getProxyManager().getList().stream()
            .filter(type -> type.getOrgMapping().equals(orgMapping))
            .sorted(comparator)
            .collect(Collectors.toList());
}
    
private TypeManager getProxyManager() {
    return (TypeManager) AopContext.currentProxy();
}<span data-mce-type="bookmark" style="display: inline-block; width: 0px; overflow: hidden; line-height: 0;" class="mce_SELRES_start"></span>

強制透過代理物件做呼叫，這樣就會啟用了 getList 的 Cache 了。

以下為 AopContext.currentProxy() 可使用的步驟：

1. Add dependency to Maven pom.xml file：

   <dependency>
       <groupId>org.aspectj</groupId>
       <artifactId>aspectjweaver</artifactId>
       <version>1.8.7</version>
   </dependency>
   

2. Add app-config.xml file (目前 java config 標注式寫法未能啟用 expose-proxy )：

   <?xml version="1.0" encoding="UTF-8"?>
   <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
       <aop:config expose-proxy="true"/>
   </beans>
   

3. import 進 AppConfig：

   @ImportResource("classpath*:/app-config.xml")
   @EnableCaching
   @Configuration
   public class CacheConfig {
   
       @Bean
       @Autowired
       public CacheManager cacheManager(final net.sf.ehcache.CacheManager cacheManager) {
           cacheManager.addCache(new Cache(getDefaultConfig(CacheConstants.FIND_ALL_TYPE)));
           cacheManager.addCache(new Cache(getDefaultConfig(CacheConstants.FIND_ONE_TYPE)));
           return new EhCacheCacheManager(cacheManager);
       }
   
       private CacheConfiguration getDefaultConfig(String name) {
           return new CacheConfiguration(name, CacheConstants.maxEntriesLocalHeap)
                   .memoryStoreEvictionPolicy(CacheConstants.memoryStoreEvictionPolicy)
                   .eternal(CacheConstants.eternal)
                   .timeToIdleSeconds(CacheConstants.timeToIdleSeconds)
                   .timeToLiveSeconds(CacheConstants.timeToLiveSeconds)
                   .maxBytesLocalDisk(CacheConstants.maxBytesLocalDisk, MemoryUnit.MEGABYTES);
       }
   
   }<span data-mce-type="bookmark" style="display: inline-block; width: 0px; overflow: hidden; line-height: 0;" class="mce_SELRES_start"></span>
   

結語：

呼，整個幾乎花近半天的時間處理它…