有时我的 API 会抛出异常,该服务器无法处理我的请求。我决定创建将重新调用 API 调用的 AOP 方面。例如,5 次,之后如果仍然不起作用,则抛出异常。
请看我的 AOP 课程。这不是一个完整的身体,但我希望你能够理解发生了什么:
@Aspect
public class RetryRequestExecutor {
....
@Around("@annotation(com.test.RequestRetriable)")
public Object retryApiRequest(ProceedingJoinPoint point) throws Throwable {
int numAttempts = 0;
ServiceException lastException;
do {
numAttempts++;
try {
preInvokeLog(point);
Object retValue = point.proceed();
postInvokeLog(point);
return retValue;
} catch (ServiceException e) {
lastException = handleServiceException(point, numAttempts, e);
}
} while (numAttempts <= maxRetries);
throw lastException;
}
....
}
这是我的服务类:
public class UserApiImpl implements UserApi {
...
@Override
public List<DomainUser> retrieveSuspendedUsers() throws Exception{
LOG.debug("Retrieving suspended users.");
...
List<DomainUser> users = new ArrayList<DomainUser>(64);
do {
//Invoke API. AOP invoke it two times!
currentPage = getUsers(retrieveUrl);
...
URL nextLink = currentPage.getNextLink();
if (nextLink == null){
break;
}
...
} while (nextLink != null);
return users;
}
@Override
@RequestRetriable
public UserFeed getUsers(URL feedUrl) throws Exception {
return userService.getFeed(feedUrl, UserFeed.class);
}
...
}
如您所见,我只注释了getUsers
方法。方法retrieveSuspendedUsers
没有注释。
Spring配置如下所示:
<aop:aspectj-autoproxy/>
现在,当我直接调用getUsers
方法时,一切正常——AOP 只调用一次。但是当我调用retrieveSuspendedUsers
方法时 - AOP 为每个页面调用它两次(我逐页检索用户,页面大小等于 100)。我可以在下面的日志中看到:
2013-03-11 13:06:40,179 DEBUG [pool-2-thread-1] Invoke API request getUsers with arguments [https://domain.com/user/2.0/]
2013-03-11 13:06:40,180 DEBUG [pool-2-thread-1] Invoke API request getUsers with arguments [https://domain.com/user/2.0/]
2013-03-11 13:06:41,745 DEBUG [pool-2-thread-1] Invoke API request getUsers with arguments [https://domain.com/user/2.0/] finished successfully
2013-03-11 13:06:41,745 DEBUG [pool-2-thread-1] Invoke API request getUsers with arguments [https://domain.com/user/2.0/] finished successfully
API 调用非常耗时,我想避免额外的、不必要的调用。如何解决这种行为?