如何在 AspectJ 中围绕建议重新抛出异常

Question

我有一些引发异常的方法，我想使用 AspectJ 来计算执行时间以及是否引发异常，并登录到错误日志并通过重新引发异常来继续流程。

我试图通过以下方式实现这一点，但 eclipse 说“未处理的异常类型”。

针对谁使用aspectj的代码：-

public interface Iface {
    public void reload() throws TException;

    public TUser getUserFromUserId(int userId, String serverId) throws ResumeNotFoundException, TException;

    public TUser getUserFromUsername(String username, String serverId) throws  ResumeNotFoundException, TException;

    public TResume getPartialActiveProfileFromUserId(int userId, int sectionsBitField, String serverId) throws ResumeNotFoundException, UserNotFoundException;

    public TResume getPartialActiveProfileFromUsername(String username, int sectionsBitField, String serverId) throws ResumeNotFoundException, UserNotFoundException, TException;
}

代码方面：-

public aspect AspectServerLog {

public static final Logger ERR_LOG = LoggerFactory.getLogger("error");

Object around() : call (* com.abc.Iface.* (..)) {
    Object ret;
    Throwable ex = null;

    StopWatch watch = new Slf4JStopWatch();

    try {
    ret = proceed();
    }catch (UserNotFoundException e) {
    ex = e ;
     throw e ;
    } catch (ResumeNotFoundException e) {
    ex = e ;
    throw e ;
    } catch (Throwable e) {
    ex = e ;
    throw new RuntimeException(e);
    }finally{

    watch.stop(thisJoinPoint.toShortString());

    if(ex!=null){
        StringBuilder mesg = new StringBuilder("Exception in ");
        mesg.append(thisJoinPoint.toShortString()).append('(');
        for(Object o : thisJoinPoint.getArgs()) {
        mesg.append(o).append(',');
        }
        mesg.append(')');

        ERR_LOG.error(mesg.toString(), ex);
        numEx++;
    }

   }
return ret;
}
}

请帮助解释为什么这个 AspectJ 不起作用。

Answer 1

您可以避免捕获异常，而只需使用没有捕获的 try/finally 块。 如果您确实需要记录异常，您可以使用 after throwing 建议，如下所示：

public aspect AspectServerLog {

    public static final Logger ERR_LOG = LoggerFactory.getLogger("error");

    Object around() : call (* com.abc.Iface.* (..)) {

        StopWatch watch = new Slf4JStopWatch();

        try {
            return proceed();
        } finally {
            watch.stop(thisJoinPoint.toShortString());
        }
    }

    after() throwing (Exception ex) : call (* com.abc.Iface.* (..)) {
        StringBuilder mesg = new StringBuilder("Exception in ");
        mesg.append(thisJoinPoint.toShortString()).append('(');
        for (Object o : thisJoinPoint.getArgs()) {
            mesg.append(o).append(',');
        }
        mesg.append(')');

        ERR_LOG.error(mesg.toString(), ex);
    }

}

Answer 2

恐怕您不能编写建议来抛出未声明为在匹配的连接点抛出的异常。每人：http://www.eclipse.org/aspectj/doc/released/progguide/semantics-advice.html： “通知声明必须包含一个 throws 子句，列出主体可能抛出的已检查异常。此已检查异常列表必须与通知的每个目标连接点兼容，否则编译器会发出错误信号。”

在 aspectj 邮件列表上已经讨论过如何改善这种情况 - 请参阅这样的主题：http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg01412.html

但基本上您需要为异常声明的每个变体提供不同的建议。例如：

Object around() throws ResumeServiceException, ResumeNotFoundException, TException: 
  call (* Iface.* (..) throws ResumeServiceException, ResumeNotFoundException, TException) {

这将在所有有这 3 个例外的地方提供建议。

Answer 3

有一个“丑陋”的解决方法 - 我在 Spring4 AbstractTransactionAspect 中找到了它们

Object around(...): ... {
    try {
        return proceed(...);
    }
    catch (RuntimeException ex) {
        throw ex;
    }
    catch (Error err) {
        throw err;
    }
    catch (Throwable thr) {
        Rethrower.rethrow(thr);
        throw new IllegalStateException("Should never get here", thr);
    }
}

/**
 * Ugly but safe workaround: We need to be able to propagate checked exceptions,
 * despite AspectJ around advice supporting specifically declared exceptions only.
 */
private static class Rethrower {

    public static void rethrow(final Throwable exception) {
        class CheckedExceptionRethrower<T extends Throwable> {
            @SuppressWarnings("unchecked")
            private void rethrow(Throwable exception) throws T {
                throw (T) exception;
            }
        }
        new CheckedExceptionRethrower<RuntimeException>().rethrow(exception);
    }
}