如何检查异常的类型以及嵌套异常的类型？

发布于 2024-11-17 07:16:47 字数 308 浏览 3 评论 0原文

假设我捕获了一个 AppException 类型的异常，但我只想在该异常具有 StreamException 类型的嵌套异常时对该异常执行某些操作。

if (e instanceof AppException)
{
    // only handle exception if it contains a
    // nested exception of type 'StreamException'

如何检查嵌套的 StreamException？

原文

Suppose I catch an exception that is of type AppException but I only want to carry out certain actions on that exception if it has a nested exception of type StreamException.

if (e instanceof AppException)
{
    // only handle exception if it contains a
    // nested exception of type 'StreamException'

How do I check for a nested StreamException?

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柳絮泡泡 2024-11-24 07:16:48

也许您可以尝试为特定目的对 AppException 进行子类化，而不是检查原因。

例如。

class StreamException extends AppException {}

try {
    throw new StreamException();
} catch (StreamException e) {
   // treat specifically
} catch (AppException e) {
   // treat generically
   // This will not catch StreamException as it has already been handled 
   // by the previous catch statement.
}

您也可以在 java 的其他地方找到这种模式。一个是示例 IOException。它是许多不同类型 IOException 的超类，包括但不限于 EOFException、FileNotFoundException 和 UnknownHostException。

Maybe instead of examining the cause you could try subclassing AppException for specific purposes.

eg.

class StreamException extends AppException {}

try {
    throw new StreamException();
} catch (StreamException e) {
   // treat specifically
} catch (AppException e) {
   // treat generically
   // This will not catch StreamException as it has already been handled 
   // by the previous catch statement.
}

You can find this pattern else where in java too. One is example IOException. It is the superclass for many different types of IOException, including, but not limited to EOFException, FileNotFoundException, and UnknownHostException.

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红颜悴 2024-11-24 07:16:48

if (e instanceof AppException) {
    boolean causedByStreamException = false;
    Exception currExp = e;
    while (currExp.getCause() != null){
        currExp = currExp.getCause();
        if (currExp instanceof StreamException){
            causedByStreamException = true;
            break;
        }
    }
    if (causedByStreamException){
       // Write your code here
    }
}

if (e instanceof AppException) {
    boolean causedByStreamException = false;
    Exception currExp = e;
    while (currExp.getCause() != null){
        currExp = currExp.getCause();
        if (currExp instanceof StreamException){
            causedByStreamException = true;
            break;
        }
    }
    if (causedByStreamException){
       // Write your code here
    }
}

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