通常,我們為了避免頻繁的查詢訪問資料庫或者第三方介面,會把查詢結果快取到redis或者memcached之類的nosql資料庫中,避免資料庫或者網路開銷過大導致程式效率太低或者雪崩效應,但是程式碼中頻繁的操作快取,會讓程式碼過於冗長,可以通過自定義註解的方式封裝快取的操作,使程式碼更簡潔,話不多說,直接上程式碼:

1.先定義註解@EnableCacheService

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface EnableCacheService {
    /**
     * key字首 
     */
 

	String keyPrefix();
    /**
     * key主體，spel表示，例：#id（取形參中id的值）
     */
    String fieldKey();
    /**
     * 過期時間 
     */
    int expireTime() default 3600;
    
    TimeUnit timeUnit() default TimeUnit.SECONDS;
    
    CacheOperation cacheOperation();
    
    /**
    * 快取操作型別
    */
    enum CacheOperation {
 

        QUERY, // 查詢
        UPDATE, // 修改
        DELETE;  // 刪除
    }
}

2.切面處理類

/**
 * EnableRedisService 註解切面處理
 * @author: Iffie
 * @date: 2018年9月29日
 */
@Aspect
@Component
@Slf4j
@SuppressWarnings("all")
public class CacheServiceAspect {

    @Pointcut("@annotation(com.iffie.core.EnableCacheService)"
 
)
    public void dealCacheServiceCut(){}
    
    @Autowired
    private RedisTemplate redisTemplate;

    @Around(value = "dealCacheServiceCut()")
    @SuppressWarnings("all")
    public Object dealCacheService(ProceedingJoinPoint point) throws Throwable{
    	Method method = getMethod(point);
    	// 獲取註解物件
    	EnableCacheService cacheServiceAnnotation = method.getAnnotation(EnableCacheService.class);
    	//所有引數
    	Object[] args = point.getArgs();
        String cacheKey = cacheServiceAnnotation.keyPrefix()+parseKey(cacheServiceAnnotation.fieldKey(), method, args);
        log.info("{} enable cache service,cacheKey:{}",point.getSignature(),cacheKey);
        CacheOperation cacheOperation = cacheServiceAnnotation.cacheOperation();
        if(cacheOperation==CacheOperation.QUERY) {
        	return processQuery(point, cacheServiceAnnotation, cacheKey);
        }
        if(cacheOperation==CacheOperation.UPDATE||cacheOperation==CacheOperation.DELETE) {
        	return processUpdateAndDelete(point, cacheKey);
        }
        return point.proceed();
    }

    /**
     * 查詢處理
     */
	private Object processQuery(ProceedingJoinPoint point, EnableCacheService cacheServiceAnnotation, String cacheKey)
			throws Throwable {
		if(redisTemplate.hasKey(cacheKey)) {
        	log.info("{} enable cache service,has cacheKey:{} , return",point.getSignature(),cacheKey);
			return redisTemplate.opsForValue().get(cacheKey);
		}else {
			Object result = null;
			try {
				return result = point.proceed();
			} finally {
				redisTemplate.opsForValue().
					set(cacheKey, result, cacheServiceAnnotation.expireTime(), cacheServiceAnnotation.timeUnit());
				log.info("after {} proceed,save result to cache,redisKey:{},save content:{}",point.getSignature(),cacheKey,result);
			}
		}
	}
	
	/**
	 *刪除和修改處理
	 */
	private Object processUpdateAndDelete(ProceedingJoinPoint point, String cacheKey)
			throws Throwable {
		//通常來講,資料庫update操作後,只需刪除掉原來在快取中的資料,下次查詢時就會重新整理
		try {
			return point.proceed();
		} finally {
			redisTemplate.delete(cacheKey);
		}
	}
    
    
    private Method getMethod(JoinPoint joinPoint) throws Exception {

        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();

        Method method = methodSignature.getMethod();

        return method;
    }
    
    /**
     * 獲取redis的key
     */
    private String parseKey(String fieldKey,Method method,Object [] args){
        //獲取被攔截方法引數名列表(使用Spring支援類庫)
        LocalVariableTableParameterNameDiscoverer u =   
            new LocalVariableTableParameterNameDiscoverer();  
        String [] paraNameArr=u.getParameterNames(method);
        
        //使用SPEL進行key的解析
        ExpressionParser parser = new SpelExpressionParser(); 
        //SPEL上下文
        StandardEvaluationContext context = new StandardEvaluationContext();
        //把方法引數放入SPEL上下文中
        for(int i=0;i<paraNameArr.length;i++){
            context.setVariable(paraNameArr[i], args[i]);
        }
        return parser.parseExpression(fieldKey).getValue(context,String.class);
    }
}

3.Demo

	@EnableCacheService(keyPrefix=Constants.USER_REDIS_KEY_PREFIX,
		fieldKey="#id",cacheOperation=CacheOperation.QUERY)
	public User expressIssueInfo(String id) {
		return userMapper.selectByPrimaryKey(id);
	}