This is the same problem you'd have with any other type of file (nothing
really excel/poi particular here). XLS is not a good database or data
transmit format its a horribly inefficient and wasteful format. I
suggest using MySQL or Postgresql. They're free and easy to
administrate (esp mysql). if you have to write to blobs use postgresql
as Mysql's blobs are not efficiently implemented.
Brian Bonner wrote:
Thanks Mark. using a semaphore or other sort of lock will probably work
as well.
I think the real solution is getting these folks to use a relational
database. It's a very small business with no IT staff.
Brian
Anthony Andrews wrote:
Hello Brian
Ages ago, we wrote an application - using Visual Basic
would you believe - that created, updated and
generally messed around with .doc files. The only
practical way we could find to overcome the same type
of problem was to write our own application to control
access to the file(s).
Put simply, when a user accessed a file, a record was
written into a log. If anyone else tried to access the
file, the first thing we did was to consult the log.
If the file had not been checked out, they were
allowed access to it, but if the file had been checked
out they were simply prevented from loading that file.
Then, as soon as a person finished with a file, it
would be rendered accessible again by being checked in
so to speak - removed from the log.
It worked but did impose some overhead and of course
that overhead became more of a problem as the volumne
of files grew and more and more users gained access to
the system.
Do not know if that helps? It may be possible to
implement something similar using a shared object that
maintains an internal ArrayList of file names and has
synchronised methods to check and update that
ArrayList.
Yours
Mark B
--- Brian Bonner <[EMAIL PROTECTED]> wrote:
It seems like I need to synchronize access to the
tags that perform these updates. Here's my rationale. My tags read
the workbook to figure out the row count and perform an insert on a
cell of a specific row and then save it back to the file. If two
requests come into this JSP at the same time, they'll both have the same
initial picture of the file (assuming it will even be read and won't
throw
a lock or FileNotFoundException) and when they update, the
last update will win.
But still this synchronization solution doesn't seem
to help at the file level. Additional thoughts?
Brian
Brian Bonner wrote:
Hi Guys,
I had a request from someone to allow them to
write forms directly to
an Excel spreadsheet. This user is not a
developer, but does do web
design and is fairly fluent with HTML, xHTML.
Anyway.
I have written a tag library to allow read/write
access to/from Excel
spreadsheets using POI. It works well, and I know
that POI is not
threadsafe.
I could synchronize access to calls made by the
tags to POI. But I'm
also concerned about a user opening up the file
and locking up the app.
Any suggestions?
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SuperLink Software, Inc.
Java to Excel using POI
http://www.superlinksoftware.com/services/poi
Commercial support including features added/implemented, bugs fixed.
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