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From "Mario Zannone (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (NET-427) In certain error/failure circumstances ftpClient.listFiles(param) returns an empty list instead of null or an exception
Date Fri, 28 Oct 2011 07:50:32 GMT
In certain error/failure circumstances ftpClient.listFiles(param) returns an empty list instead
of null or an exception
-----------------------------------------------------------------------------------------------------------------------

                 Key: NET-427
                 URL: https://issues.apache.org/jira/browse/NET-427
             Project: Commons Net
          Issue Type: Bug
          Components: FTP
    Affects Versions: 3.0.1
         Environment: SunOS 5.10 Generic_144489-06
            Reporter: Mario Zannone
            Priority: Minor


According to the API docs ftpClient.listFiles(String) should return
null or an exception on error conditions or failure:

 The convention for all the FTP command methods in FTPClient is
 such that they either return a boolean value or some other value.
 The boolean methods return true on a successful completion reply
 from the FTP server and false on a reply resulting in an error
 condition or failure. The methods returning a value other than
 boolean return a value containing the higher level data produced
 by the FTP command, or null if a reply resulted in an error
 condition or failure.

( http://commons.apache.org/net/apidocs/org/apache/commons/net/ftp/FTPClient.html )

However in certain error/failure circumstances listFiles(param)
returns an empty list instead of null.

Note that an empty list is a correct response when param does not
match any file.

We were able to bypass the problem checking the ftp reply with
getReplyCode().  However, this listFiles behaviour is unexpected 
and should at least be documented.

The error is not systematic and not easy to diagnose or replicate.
We were able to reproduce it using cron to run the attached
program every minute on a slow and unreliable connection;
in 24h the error did show only a couple of times.

Attachments: test program and excerpt from the test log.


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