玩转Spring Cache --- 开启基于注解的缓存功能@EnableCaching原理了解【享学Spring】(上)

@EnableCaching
@Configuration
public class CacheConfig {
    @Bean
    public ConcurrentMapCacheManager cacheManager() {
        ConcurrentMapCacheManager cacheManager = new ConcurrentMapCacheManager();
        //cacheManager.setStoreByValue(true); //true表示缓存一份副本，否则缓存引用
        return cacheManager;
    }
}

@Service
public class CacheDemoServiceImpl implements CacheDemoService {
    @Cacheable(cacheNames = "demoCache", key = "#id")
    @Override
    public Object getFromDB(Integer id) {
        System.out.println("模拟去db查询~~~" + id);
        return "hello cache...";
    }
}

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {RootConfig.class, CacheConfig.class})
public class TestSpringBean {
    @Autowired
    private CacheDemoService cacheDemoService;
    @Autowired
    private CacheManager cacheManager;
    @Test
    public void test1() {
        cacheDemoService.getFromDB(1);
        cacheDemoService.getFromDB(1);
        // 校验缓存里的内容~~~~
        Cache demoCache = cacheManager.getCache("demoCache");
        System.out.println(demoCache.getName());
        System.out.println(demoCache.get(1, String.class));
    }
}

模拟去db查询~~~1
---------------------------------
demoCache
hello cache...

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class)
public @interface EnableCaching {
  boolean proxyTargetClass() default false;
  AdviceMode mode() default AdviceMode.PROXY;
  int order() default Ordered.LOWEST_PRECEDENCE;
}

public class CachingConfigurationSelector extends AdviceModeImportSelector<EnableCaching> {
  ...
  static {
    ClassLoader classLoader = CachingConfigurationSelector.class.getClassLoader();
    jsr107Present = ClassUtils.isPresent("javax.cache.Cache", classLoader);
    jcacheImplPresent = ClassUtils.isPresent(PROXY_JCACHE_CONFIGURATION_CLASS, classLoader);
  }
  // 绝大多数情况下我们不会使用ASPECTJ，若要使用它还得额外导包~
  // getAspectJImports()这个方法略
  @Override
  public String[] selectImports(AdviceMode adviceMode) {
    switch (adviceMode) {
      case PROXY:
        return getProxyImports();
      case ASPECTJ:
        return getAspectJImports();
      default:
        return null;
    }
  }
  // 向容器导入了AutoProxyRegistrar和ProxyCachingConfiguration
  // 若JSR107的包存在(导入了javax.cache:cache-api这个包)，并且并且存在ProxyJCacheConfiguration这个类
  // 显然ProxyJCacheConfiguration这个类我们一般都不会导进来~~~~  所以JSR107是不生效的。   但是但是Spring是支持的，非常良心
  private String[] getProxyImports() {
    List<String> result = new ArrayList<>(3);
    result.add(AutoProxyRegistrar.class.getName());
    result.add(ProxyCachingConfiguration.class.getName());
    if (jsr107Present && jcacheImplPresent) {
      result.add(PROXY_JCACHE_CONFIGURATION_CLASS);
    }
    return StringUtils.toStringArray(result);
  }
  ...
}