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

// @since 3.1  内部注入的Bean角色都是ROLE_INFRASTRUCTURE  建议先看下面的父类
@Configuration
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class ProxyCachingConfiguration extends AbstractCachingConfiguration {
  // 缓存注解的增强器：重点在CacheOperationSource和CacheInterceptor
  @Bean(name = CacheManagementConfigUtils.CACHE_ADVISOR_BEAN_NAME)
  @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
  public BeanFactoryCacheOperationSourceAdvisor cacheAdvisor() {
    BeanFactoryCacheOperationSourceAdvisor advisor = new BeanFactoryCacheOperationSourceAdvisor();
    advisor.setCacheOperationSource(cacheOperationSource());
    advisor.setAdvice(cacheInterceptor());
    if (this.enableCaching != null) {
      advisor.setOrder(this.enableCaching.<Integer>getNumber("order"));
    }
    return advisor;
  }
  // 关于CacheOperationSource和CacheInterceptor是理解注解原理重要的两个类，放在下一章节讲解更妥
  // 注意CacheOperationSource是给CacheInterceptor用的
  @Bean
  @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
  public CacheOperationSource cacheOperationSource() {
    return new AnnotationCacheOperationSource();
  }
  @Bean
  @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
  public CacheInterceptor cacheInterceptor() {
    CacheInterceptor interceptor = new CacheInterceptor();
    interceptor.configure(this.errorHandler, this.keyGenerator, this.cacheResolver, this.cacheManager);
    interceptor.setCacheOperationSource(cacheOperationSource());
    return interceptor;
  }
}
// 抽象父类：定义和管理了Caching相关的API、类们
@Configuration
public abstract class AbstractCachingConfiguration implements ImportAware {
  // 这些属性都是protected的，子类可以直接访问哦~~~
  @Nullable
  protected AnnotationAttributes enableCaching;
  @Nullable
  protected Supplier<CacheManager> cacheManager;
  @Nullable
  protected Supplier<CacheResolver> cacheResolver; // 缓存注解的处理器
  @Nullable
  protected Supplier<KeyGenerator> keyGenerator; // key的生成器
  @Nullable
  protected Supplier<CacheErrorHandler> errorHandler; // 错误处理器
  // 继承此抽象类前提条件：必须标注@EnableCaching注解~
  @Override
  public void setImportMetadata(AnnotationMetadata importMetadata) {
    this.enableCaching = AnnotationAttributes.fromMap(importMetadata.getAnnotationAttributes(EnableCaching.class.getName(), false));
    if (this.enableCaching == null) {
      throw new IllegalArgumentException("@EnableCaching is not present on importing class " + importMetadata.getClassName());
    }
  }
  // 可以通过实现CachingConfigurer接口来**指定缓存使用的默认**的：
  // 缓存管理器
  // 缓存解析器
  // key生成器
  // 错误处理器
  @Autowired(required = false)
  void setConfigurers(Collection<CachingConfigurer> configurers) {
    if (CollectionUtils.isEmpty(configurers)) {
      return;
    }
    // CachingConfigurer的实现类，最多只能有一个
    if (configurers.size() > 1) {
      throw new IllegalStateException(configurers.size() + " implementations of " +
          "CachingConfigurer were found when only 1 was expected. " +
          "Refactor the configuration such that CachingConfigurer is " +
          "implemented only once or not at all.");
    }
    CachingConfigurer configurer = configurers.iterator().next();
    useCachingConfigurer(configurer);
  }
  /**
   * Extract the configuration from the nominated {@link CachingConfigurer}.
   */
  protected void useCachingConfigurer(CachingConfigurer config) {
    this.cacheManager = config::cacheManager;
    this.cacheResolver = config::cacheResolver;
    this.keyGenerator = config::keyGenerator;
    this.errorHandler = config::errorHandler;
  }
}