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Date: Tue, 09 Dec 2008 11:33:19 +0800
From: Regis <xu.regis@gmail.com>
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To: dev@harmony.apache.org
Subject: Re: [classlib] [luni] Should Improve File System Exception Messages
References: <297100561.1228445444854.JavaMail.jira@brutus>
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I found readImpl and writeImpl in OSFileSystem.c use

netLookupErrorString(env, HYPORT_ERROR_FILE_LOCKED)

to get error messages, which are hard coded in nethelp.c, my questions are:

1. why does file read/write need to get error messages from nethelp.c? 
We already have hyfile_error_message() can do that.

2. error messages are hard coded in netLookupErrorString, is that expected?


Tim Ellison wrote:
> 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
> 

Best Regards,
Regis.