Java：如何向 try catch 主体内的方法调用者抛出异常？
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Java: How to throw an Exception to the method caller inside a try catch body?
提问by Martijn Courteaux
When I have a method like this:
当我有这样的方法时：
public static void foo(String param) throws IOException
{
try
{
// some IOoperations
if (param.isEmpty())
{
throw new IOException("param is empty");
}
// some other IOoperations
} catch (Exception e) {
/* handle some possible errors of of the IOoperations */
}
}
And when the IOException ("param is empty") is thrown, it is catched by the try-catchin that body. But this exception is meant for the caller of this method. How can I do this properly? Is there something "pure-Java" to do this or do I have to create an other type of Exception which is not an instance of IOException to avoid the try-catch body will handle it?
当抛出 IOException ("param is empty") 时，它会被该try-catch主体中的捕获。但是这个异常是针对这个方法的调用者的。我怎样才能正确地做到这一点？有什么“纯Java”可以做到这一点，还是我必须创建其他类型的异常，它不是 IOException 的实例，以避免 try-catch 主体处理它？
I know you would suggest to use a IllegalArgumentExceptionin this case. But this is a simplified example of my situation. In fact the Exception Ithrow is an IOException.
我知道你会建议IllegalArgumentException在这种情况下使用 a 。但这是我的情况的一个简化示例。事实上，我抛出的异常是一个 IOException。
Thanks
谢谢
回答by Nikita Rybak
Making your own custom subclass of IOExceptionmight be a good idea. Not only to solve this problem, but sometimes it's a bit 'user-friendlier' for your API users.
制作您自己的自定义子类IOException可能是一个好主意。不仅要解决这个问题，而且有时它对您的 API 用户来说有点“用户友好”。
Then you could ignore it in catch block (rethrow it immediately)
然后你可以在 catch 块中忽略它（立即重新抛出它）
} catch (FooIOException e) {
throw e;
} catch (Exception e) {
/* handle some possible errors of of the IOoperations */
}
回答by andersoj
I think I'm confused by the specifics of your example -- why are you making the broad
我想我对你的例子的细节感到困惑——你为什么要广泛
} catch (Exception e) {
If that overly-generic catch clause wasn't there, your problem would go away.
如果那个过于通用的 catch 子句不存在，你的问题就会消失。
Did I misunderstand?
我误会了吗？
回答by tangens
You can check if your exception is an instance of IOExceptionand if it is, rethrow it.
您可以检查您的异常是否是一个实例，IOException如果是，则重新抛出它。
catch( Exception e ) {
if( e instanceof IOException ) {
throw (IOException)e;
}
}
回答by Codemwnci
You can catch it, and re-throw it, but the correct solution should be to be more selective of what you are catching in your catch statement....
你可以抓住它，然后重新抛出它，但正确的解决方案应该是在你的 catch 语句中更有选择性地捕捉到什么......
For example. In the code below, I am catching a FileNotFoundException, so the IOException is thrown back to the calling method.
例如。在下面的代码中，我捕获了 FileNotFoundException，因此将 IOException 抛回调用方法。
public static void foo(String param) throws IOException {
try {
// some IOoperations
if (param.isEmpty())
{
throw new IOException("param is empty");
}
// some other IOoperations
} catch (FileNotFoundException e) {
/* handle some possible errors of of the IOoperations */
}
}
回答by Anon
I would create a subclass of IOException. This will let you use an instanceofcheck and rethrow.
我会创建一个IOException. 这将让您使用instanceof检查并重新抛出。
And there are very few cases where I use catch (Exception). It's almost always better to catch specific exceptions. The only reason not to is when you want to aggregate exceptions and rethrow (reflection operations are a common place to do this).
而且我在极少数情况下使用catch (Exception). 捕获特定异常几乎总是更好。不这样做的唯一原因是当您想要聚合异常并重新抛出时（反射操作是执行此操作的常见地方）。
回答by Colin Hebert
If IOExceptions are meant for the foo()caller, you can do this:
如果 IOExceptions 是给foo()调用者的，你可以这样做：
public static void foo(String param) throws IOException
{
try
{
// some IOoperations
if (param.isEmpty())
{
throw new IOException("param is empty");
}
// some other IOoperations
} catch (IOException e) {
throw e;
} catch (Exception e) {
/* handle some possible errors of of the IOoperations */
}
}
If your exception is the only one really needed to be rethrown, then create a new Subtype of IOException name it MyExceptionan try to catch MyExceptionto rethrow it.
如果您的异常是唯一真正需要重新抛出的异常，则创建一个新的 IOException 子类型，将其命名MyException为尝试捕获MyException以重新抛出它。
Any pokemon exception handling is very ugly !
任何口袋妖怪异常处理都非常丑陋！
