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From Tim Ellison <t.p.elli...@gmail.com>
Subject [classlib] [luni] Should Improve File System Exception Messages
Date Fri, 05 Dec 2008 16:42:54 GMT
Regis wrote:
> Jim Yu wrote:
>> 2008/12/5 Regis <xu.regis@gmail.com>
>>> Kevin Zhou wrote:
>>>
>>>> The FileNotFoundException is being thrown by the constructor of
>>>> FileOutputStream when that constructor is attempting to open File f for
>>>> writing and it doesn't have permission to do so.
>>>>
>>>> To open f the FileOutputStream class is calling
>>>> org.apache.harmony.luni.platform.OSFileSystem.open(). The
>>>> o.a.h.l.p.OSFileSystem.open() method invokes a native openImpl()
>>>> method.
>>>> The
>>>> native method can fail for several reasons. The problem lies in the
>>>> fact
>>>> that the reason behind the failure of the native method isn't being
>>>> propagated back to the FileOutputStream which is creating the
>>>> FileNotFoundException upon failure.
>>>>
>>> Yes, the native code just return -1 to indicate an error occurred,
>>> while in
>>> hyfile.c::hyfile_open, error messages are set by
>>> portLibrary->error_set_last_error, but the caller never use them. So I
>>> suggest to add a method in OSFileSystem.c to retrieve the error
>>> messages.
>>> The java could get the failure reasons when the native return -1, and
>>> add
>>> them to the exception message.
>>
>>
>> Agree to add a method for retrieving the error message from Port Library
>> which can be invoked by Java code. Maybe there are more cases which
>> have the
>> similar requirements of retrieving the error message.
>
> Yes, we could supply the utility function first, and then use it when
> needed. If no one object I would like to add this function.

How about raising the exception (with the right message) in the openImpl
native code rather than just returning -1 and crossing the JNI-boundary
again to find the reason?

There are other cases (i.e. other than FileNotFound) that you might want
to distinguish through IOExceptions too.

Regards,
Tim

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