Re: BigDecimal WOes
Re: BigDecimal WOes
- Subject: Re: BigDecimal WOes
- From: Chuck Hill <email@hidden>
- Date: Sat, 22 Nov 2008 19:11:03 -0800
On Nov 22, 2008, at 6:44 PM, Neil MacLennan wrote:
I'm having trouble with BigDecimal, WO and my database. You know how
some people have trouble with dates amd time zones? Well I've never
quite mastered the finer idiosyncrasies of floating point numbers in
Java.
I have an EO attribute, 'amount' -- a currency value you'll not be
surprised to hear. It's decimal field in my database (MySQL) and a
BigDecimal in my model.
I'm aware of "issues" with BigDecimal when you use the
BigDecimal(double) contructor and so I've been using the better
BigDecimal(String) constructor.
When I first insert my EO (containing "amount") and saveChanges --
it works fine. The value in the DB is as expected, say, 16.16,
representing 16 pounds and 16 pence.
When I next come to update that row I get a JDBC error and an
EOGeneralAdaptorException failure.
I turned on logging in MySQL (Wonder SQL logging wasn't too helpful)
to see what was happening: the UPDATE transaction is being rolled
back because the row could not be sucessfully updated. Here's why:
[MySQL Log]
2 Prepare [4] UPDATE OrderTicket SET paymentStatus = ? WHERE
(ticketID = ? AND amount = ? AND orderID = ? AND paymentStatus = ?
AND paymentTimestamp is NULL AND shopID = ?)
2 Execute [4] UPDATE OrderTicket SET paymentStatus =
'Authorising with Provider...' WHERE (ticketID = 5824 AND amount =
16.159999847412 AND orderID = 127 AND paymentStatus = 'Taking Card
Details...' AND paymentTimestamp is NULL AND shopID = 3)
2 Query rollback
[END]
For some reason, WO is using this imprecise floating value
(16.159999847412) in the DB lock to UPDATE against. But I'm stumped
where it's getting this from. Is it reading it back in again from
the DB at some point and because the database has the "amount" field
as a decimal it's using the BigDecimal(double) contructor? Should I
only use string (varchar/char) db fields for use with BigDecimal?
I've "fixed" the issue by not having WO lock on the amount attribute
in my model, but that doesn't fix the underlying problem: it just
avoids it. What's the real answer?
How is the attribute defined in the model? It sounds like the value
type might be wrong.
Chuck
--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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