转自：聊聊如何基于spring @Cacheable扩展实现缓存自动过期时间以及自动刷新-腾讯云开发者社区-腾讯云 (tencent.com)

前言

用过spring cache的朋友应该会知道，Spring Cache默认是不支持在@Cacheable上添加过期时间的，虽然可以通过配置缓存容器时统一指定。形如

@Bean
public CacheManager cacheManager(
        @SuppressWarnings("rawtypes") RedisTemplate redisTemplate) {
   RedisCacheManager cacheManager= new RedisCacheManager(redisTemplate);
    cacheManager.setDefaultExpiration(60);
    Map expiresMap = new HashMap<>();
    expiresMap.put("customUser",30L);
    cacheManager.setExpires(expiresMap);
    return cacheManager;
}

复制

但有时候我们会更习惯通过注解指定过期时间。今天我们就来聊一下如何扩展@Cacheable实现缓存自动过期以及缓存即将到期自动刷新

2

实现注解缓存过期前置知识

SpringCache包含两个顶级接口，Cache和CacheManager，通过CacheManager可以去管理一堆Cache。因此我们要扩展@Cacheable，就脱离不了对Cache和CacheManager进行扩展

其次要实现过期时间，首先是引入的缓存产品，他本身就要支持过期时间，比如引入的缓存为ConcurrentHashMap，他原本就是不支持过期时间，如果要扩展，就要非常耗费精力实现

3

实现注解缓存过期

01

方法一：通过自定义cacheNames方式

形如下

@Cacheable(cacheNames = "customUser#30", key = "#id")

复制

通过#分隔，#后面部分代表过期时间（单位为秒）

实现逻辑步骤为：

1、自定义缓存管理器并继承RedisCacheManager，同时重写createRedisCache方法

示例：

public class CustomizedRedisCacheManager extends RedisCacheManager {
    public CustomizedRedisCacheManager(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration) {
        super(cacheWriter, defaultCacheConfiguration);
    }
    @Override
    protected RedisCache createRedisCache(String name, RedisCacheConfiguration cacheConfig) {
        String[] array = StringUtils.delimitedListToStringArray(name, "#");
        name = array[0];
        if (array.length > 1) {
            long ttl = Long.parseLong(array[1]);
            cacheConfig = cacheConfig.entryTtl(Duration.ofSeconds(ttl)); 
        }
        return super.createRedisCache(name, cacheConfig);
    }
}

复制

2、将默认的缓存管理器改成我们自定义的缓存管理器

示例：

@EnableCaching 
@Configuration
public class CacheConfig {
    @Bean
    public CacheManager cacheManager() {
        RedisCacheConfiguration defaultCacheConfig = RedisCacheConfiguration.defaultCacheConfig()
                .entryTtl(Duration.ofDays(1));
        CustomizedRedisCacheManager redisCacheManager = new CustomizedRedisCacheManager(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory()), defaultCacheConfig);
        return redisCacheManager;
    }
}

复制

通过如上2个步骤，即可实现缓存过期

02

方法二：通过自定义派生@Cacheable注解

第一种方法的实现是简单，但缺点是语义不直观，因此得做好宣导以及wiki，不然对于新人来说，他可能都不知道cacheName用#分割是代表啥意思

方法二的实现逻辑步骤如下

1、自定义注解LybGeekCacheable

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@Cacheable(cacheManager = CacheConstant.CUSTOM_CACHE_MANAGER,keyGenerator = CacheConstant.CUSTOM_CACHE_KEY_GENERATOR)
public @interface LybGeekCacheable {
  @AliasFor(annotation = Cacheable.class,attribute = "value")
  String[] value() default {};
  @AliasFor(annotation = Cacheable.class,attribute = "cacheNames")
  String[] cacheNames() default {};
  @AliasFor(annotation = Cacheable.class,attribute = "key")
  String key() default "";
  @AliasFor(annotation = Cacheable.class,attribute = "keyGenerator")
  String keyGenerator() default "";
  @AliasFor(annotation = Cacheable.class,attribute = "cacheResolver")
  String cacheResolver() default "";
  @AliasFor(annotation = Cacheable.class,attribute = "condition")
  String condition() default "";
  @AliasFor(annotation = Cacheable.class,attribute = "unless")
  String unless() default "";
  @AliasFor(annotation = Cacheable.class,attribute = "sync")
  boolean sync() default false;
   long expiredTimeSecond() default 0;
   long preLoadTimeSecond() default 0;
}

复制

大部分注解和@Cacheable保持一致，新增expiredTimeSecond缓存过期时间以及缓存自动刷新时间preLoadTimeSecond

2、自定义缓存管理器并继承RedisCacheManager并重写loadCaches和createRedisCache

public class CustomizedRedisCacheManager extends RedisCacheManager implements BeanFactoryAware {
    private Map initialCacheConfigurations;
    private RedisTemplate cacheRedisTemplate;
    private RedisCacheWriter cacheWriter;
    private DefaultListableBeanFactory beanFactory;
    private RedisCacheConfiguration defaultCacheConfiguration;
    protected CachedInvocation cachedInvocation;
    public CustomizedRedisCacheManager(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration, Map initialCacheConfigurations,RedisTemplate cacheRedisTemplate) {
        super(cacheWriter, defaultCacheConfiguration, initialCacheConfigurations);
        this.initialCacheConfigurations = initialCacheConfigurations;
        this.cacheRedisTemplate = cacheRedisTemplate;
        this.cacheWriter = cacheWriter;
        this.defaultCacheConfiguration = defaultCacheConfiguration;
        //采用spring事件驱动亦可
        //EventBusHelper.register(this);
    }
    public Map getInitialCacheConfigurations() {
        return initialCacheConfigurations;
    }
    @Override
    protected Collection loadCaches() {
        List caches = new LinkedList<>();
        for (Map.Entry entry : getInitialCacheConfigurations().entrySet()) {
            caches.add(createRedisCache(entry.getKey(), entry.getValue()));
        }
        return caches;
    }
    @Override
    public RedisCache createRedisCache(String name, @Nullable RedisCacheConfiguration cacheConfig) {
       CustomizedRedisCache customizedRedisCache = new CustomizedRedisCache(name, cacheWriter, cacheConfig != null ? cacheConfig : defaultCacheConfiguration);
       return customizedRedisCache;
    }
}

复制

3、在spring bean初始化完成后,设置缓存过期时间，并重新初始化缓存。

Component
@Slf4j
public class CacheExpireTimeInit implements SmartInitializingSingleton, BeanFactoryAware {
    
    private DefaultListableBeanFactory beanFactory;
    
    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = (DefaultListableBeanFactory)beanFactory;
    }
    @Override
    public void afterSingletonsInstantiated() {
        Map beansWithAnnotation = beanFactory.getBeansWithAnnotation(Component.class);
        if(MapUtil.isNotEmpty(beansWithAnnotation)){
            for (Object cacheValue : beansWithAnnotation.values()) {
                ReflectionUtils.doWithMethods(cacheValue.getClass(), method -> {
                    ReflectionUtils.makeAccessible(method);
                    boolean cacheAnnotationPresent = method.isAnnotationPresent(LybGeekCacheable.class);
                    if(cacheAnnotationPresent){
                         LybGeekCacheable lybGeekCacheable = method.getAnnotation(LybGeekCacheable.class);
                          CacheHelper.initExpireTime(lybGeekCacheable);
                    }
                });
            }
            CacheHelper.initializeCaches();
        }
    }

复制

注： 为啥要重新初始化缓存，主要是为了一开始默认的是没设置缓存过期，重新初始化是为了设置过期时间。为啥调用initializeCaches（）这个方法，看下官方描述就知道了

/**
   * Initialize the static configuration of caches.
   * 
Triggered on startup through {@link #afterPropertiesSet()};
   * can also be called to re-initialize at runtime.
   * @since 4.2.2
   * @see #loadCaches()
   */
  public void initializeCaches() {
    Collection caches = loadCaches();
    synchronized (this.cacheMap) {
      this.cacheNames = Collections.emptySet();
      this.cacheMap.clear();
      Set cacheNames = new LinkedHashSet<>(caches.size());
      for (Cache cache : caches) {
        String name = cache.getName();
        this.cacheMap.put(name, decorateCache(cache));
        cacheNames.add(name);
      }
      this.cacheNames = Collections.unmodifiableSet(cacheNames);
    }
  }

复制

他就是在运行的时候，可以重新初始化缓存

4、将默认的缓存管理器改成我们自定义的缓存管理器

@Bean(CacheConstant.CUSTOM_CACHE_MANAGER)
    public CacheManager cacheManager(RedisConnectionFactory connectionFactory,RedisTemplate cacheRedisTemplate) {
        RedisCacheWriter redisCacheWriter = RedisCacheWriter.nonLockingRedisCacheWriter(connectionFactory);
        RedisCacheConfiguration defaultCacheConfig = RedisCacheConfiguration.defaultCacheConfig()
                .entryTtl(Duration.ofDays(1));
        Map initialCacheConfiguration = new HashMap<>();
        return new CustomizedRedisCacheManager(redisCacheWriter,defaultCacheConfig,initialCacheConfiguration,cacheRedisTemplate);
    }

复制

5、测试

@LybGeekCacheable(cacheNames = "customUser", key = "#id",expiredTimeSecond = 30)
    public User getUserFromRedisByCustomAnno(String id){
        System.out.println("get user with id by custom anno: 【" + id + "】");
        Faker faker = Faker.instance(Locale.CHINA);
        return User.builder().id(id).username(faker.name().username()).build();
    }

复制

@Test
    public void testCacheExpiredAndPreFreshByCustom() throws Exception{
        System.out.println(userService.getUserFromRedisByCustomAnno("1"));
    }

复制

以上就是扩展缓存过期的实现主要方式了，接下来我们来聊一下缓存自动刷新

4

缓存自动刷新

一般来说，当缓存失效时，请求就会打到后端的数据库上，此时可能就会造成缓存击穿现象。因此我们在缓存即将过期时主动刷新缓存，提高缓存的命中率，进而提高性能。

spring4.3的@Cacheable提供了一个sync属性。当缓存失效后，为了避免多个请求打到数据库,系统做了一个并发控制优化，同时只有一个线程会去数据库取数据其它线程会被阻塞

5

缓存即将到期自动刷新

1、封装缓存注解对象CachedInvocation

/**
 * @description: 标记了缓存注解的方法类信息,用于主动刷新缓存时调用原始方法加载数据
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public final class CachedInvocation {
    private CacheMetaData metaData;
    private Object targetBean;
    private Method targetMethod;
    private Object[] arguments;
    public Object invoke()
            throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        final MethodInvoker invoker = new MethodInvoker();
        invoker.setTargetObject(this.getTargetBean());
        invoker.setArguments(this.getArguments());
        invoker.setTargetMethod(this.getTargetMethod().getName());
        invoker.prepare();
        return invoker.invoke();
    }
}

复制

2、编写一个获取即将到期时间参数切面，并进行事件发布调用对象CachedInvocation

@Component
@Aspect
@Slf4j
@Order(2)
public class LybGeekCacheablePreLoadAspect {
    @Autowired
    private ApplicationContext applicationContext;
    @SneakyThrows
    @Around(value = "@annotation(lybGeekCacheable)")
    public Object around(ProceedingJoinPoint proceedingJoinPoint,LybGeekCacheable lybGeekCacheable){
        buildCachedInvocationAndPushlish(proceedingJoinPoint,lybGeekCacheable);
        Object result = proceedingJoinPoint.proceed();
        return result;
    }
    private void buildCachedInvocationAndPushlish(ProceedingJoinPoint proceedingJoinPoint,LybGeekCacheable lybGeekCacheable){
        Method method = this.getSpecificmethod(proceedingJoinPoint);
        String[] cacheNames = getCacheNames(lybGeekCacheable);
        Object targetBean = proceedingJoinPoint.getTarget();
        Object[] arguments = proceedingJoinPoint.getArgs();
        KeyGenerator keyGenerator = SpringUtil.getBean(CacheConstant.CUSTOM_CACHE_KEY_GENERATOR,KeyGenerator.class);
        Object key = keyGenerator.generate(targetBean, method, arguments);
        CachedInvocation cachedInvocation = CachedInvocation.builder()
                .arguments(arguments)
                .targetBean(targetBean)
                .targetMethod(method)
                .metaData(CacheMetaData.builder()
                        .cacheNames(cacheNames)
                        .key(key)
                        .expiredTimeSecond(lybGeekCacheable.expiredTimeSecond())
                        .preLoadTimeSecond(lybGeekCacheable.preLoadTimeSecond())
                        .build()
                )
                .build();
      // EventBusHelper.post(cachedInvocation);
        applicationContext.publishEvent(cachedInvocation);
    }

复制

3、自定义缓存管理器，接收CachedInvocation

示例

public class CustomizedRedisCacheManager extends RedisCacheManager implements BeanFactoryAware {
 
    //@Subscribe
    @EventListener
    private void doWithCachedInvocationEvent(CachedInvocation cachedInvocation){
        this.cachedInvocation = cachedInvocation;
    }

复制

4、自定义cache并重写get方法

@Slf4j
public class CustomizedRedisCache extends RedisCache {
    private ReentrantLock lock = new ReentrantLock();
    public CustomizedRedisCache(String name, RedisCacheWriter cacheWriter, RedisCacheConfiguration cacheConfig) {
        super(name, cacheWriter,cacheConfig);
    }
    @Override
    @Nullable
    public ValueWrapper get(Object key) {
        ValueWrapper valueWrapper = super.get(key);
        CachedInvocation cachedInvocation = CacheHelper.getCacheManager().getCachedInvocation();
        long preLoadTimeSecond = cachedInvocation.getMetaData().getPreLoadTimeSecond();
        if(ObjectUtil.isNotEmpty(valueWrapper) && preLoadTimeSecond > 0){
            String cacheKey = createCacheKey(key);
            RedisTemplate cacheRedisTemplate = CacheHelper.getCacheManager().getCacheRedisTemplate();
            Long ttl = cacheRedisTemplate.getExpire(cacheKey, TimeUnit.SECONDS);
            if(ObjectUtil.isNotEmpty(ttl) && ttl <= preLoadTimeSecond){
                log.info(">>>>>>>>>>> cacheKey：{}, ttl: {},preLoadTimeSecond: {}",cacheKey,ttl,preLoadTimeSecond);
                ThreadPoolUtils.execute(()->{
                     lock.lock();
                     try{
                         CacheHelper.refreshCache(super.getName());
                     }catch (Exception e){
                         log.error("{}",e.getMessage(),e);
                     }finally {
                         lock.unlock();
                     }
                });
            }
        }
        return valueWrapper;
    }

}

复制

5、缓存即将到期主动刷新缓存方法

public static void refreshCache(String cacheName){
        boolean isMatchCacheName = isMatchCacheName(cacheName);
        if(isMatchCacheName){
            CachedInvocation cachedInvocation = getCacheManager().getCachedInvocation();
            boolean invocationSuccess;
            Object computed = null;
            try {
                computed = cachedInvocation.invoke();
                invocationSuccess = true;
            } catch (Exception ex) {
                invocationSuccess = false;
                log.error(">>>>>>>>>>>>>>>>> refresh cache fail",ex.getMessage(),ex);
            }
            if (invocationSuccess) {
                    Cache cache = getCacheManager().getCache(cacheName);
                    if(ObjectUtil.isNotEmpty(cache)){
                        Object cacheKey = cachedInvocation.getMetaData().getKey();
                        cache.put(cacheKey, computed);
                        log.info(">>>>>>>>>>>>>>>>>>>> refresh cache with cacheName-->【{}】，key--> 【{}】 finished !",cacheName,cacheKey);
                    }
            }
        }
    }

复制

6、测试

@LybGeekCacheable(cacheNames = "customUserName", key = "#username",expiredTimeSecond = 20,preLoadTimeSecond = 15)
    public User getUserFromRedisByCustomAnnoWithUserName(String username){
        System.out.println("get user with username by custom anno: 【" + username + "】");
        Faker faker = Faker.instance(Locale.CHINA);
        return User.builder().id(faker.idNumber().valid()).username(username).build();
    }

复制

@Test
    public void testCacheExpiredAndPreFreshByCustomWithUserName() throws Exception{
        System.out.println(userService.getUserFromRedisByCustomAnnoWithUserName("zhangsan"));
        TimeUnit.SECONDS.sleep(5);
        System.out.println("sleep 5 second :" + userService.getUserFromRedisByCustomAnnoWithUserName("zhangsan"));
        TimeUnit.SECONDS.sleep(10);
        System.out.println("sleep 10 second :" + userService.getUserFromRedisByCustomAnnoWithUserName("zhangsan"));
        TimeUnit.SECONDS.sleep(5);
        System.out.println("sleep 5 second :" + userService.getUserFromRedisByCustomAnnoWithUserName("zhangsan"));
    }

复制

6

总结

本文主要介绍了如何基于spring @Cacheable扩展实现缓存自动过期时间以及缓存即将到期自动刷新。

不知道有没有朋友会有疑问，为啥@Cacheable不提供一个ttl属性，毕竟也不是很难。在我看来，spring更多提供的是一个通用的规范和标准，如果定义的缓存，本身不支持ttl，你在@Cacheable里面配置ttl就不合适了，有时候实现一个组件或者框架，考虑的是不是能不能实现，而是有没有必要实现，更多是一种权衡和取舍