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lydia westland

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since Feb 24, 2002
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Recent posts by lydia westland

Can anyone give me some suggesion on the existing connection pool package?
Here is the problem I have with one of my customer site.
They are using MS SQL Server 2000, Java 1.4 and ODBC on Win 2000.
for the database connection, I didn't use connection pool but just reused several database connections again and again. When there is only 40 clients connected, it's working great. However, when the number of clients connected goes to 90 or more, the ODBC connection starts aborting SQL execution and database connection starts broken.
I think connection pool is the only way for me to resolve the problem. I should not re-invent the wheel. Can anyone give me good general connection pools for ODBC connection? I really appreciate that.
Thank you.
I am a lazy program. I just want to click, click, and click when doing installation. I haven't tried the current 5.0 Tomcat. when using Tomcat 4.0, I have to setup those environment variables by myself. that's painful.
Where can I find the binary window installer? Thank you very much.
18 years ago
I am thinking if it's possible for me to get a neat installer for Tomcat 4x? I can do it step by step, but just take too much time. Can anyone provide a better way to install rather do it from unzip files? Thank you very much.
18 years ago
In OOAD, we have Domain Model and Design Model. We also have different prespectives for class diagram, including conceptual perspective, specification perspective, and implementation perspective. Is the Domain Model equal to Conceptual Perspective of Class Diagram, and Design Model equals to Specification Perspective of class diagram? Thank you for clarification.
is the extreme programming created because the software product is so easy to have bugs? so they suggest there should be two person programming together?
19 years ago
I have a problem with Tomcat. My application is web signup with Tomcat as webserver. Seems every 4 or 5 users got a white screen for a couple of minutes, then it's working well again. The white screen is periodical, not for every user. I am using sessions, and the white screen occurs at the last part of "Logout". When user logout, I just invalidate his current session.
if (session!=null)
// not sure why the session still exists!
res.sendRedirect( res.encodeRedirectURL(serverBase) );
Can anyone give me some glues of what may cause the white screen? I am using Tomcat 4.0. Does Tomcat has newer version for me to test it out?
19 years ago

use the power of the database to create "views" which are denormalised and more appropriate to your scheduling, but keep the algorithms themselves out in the easily-changed, easily reused, easily understood, easily tested O-O world.

Frank, I like your points. but scheduling does need a lot of existing infomation in the database. I am afraid if the performance will be affected if I have too many ResultSet operations. In addition, I can use only one stored procedure to make it. if not, I have to write hundrends of lines of codes in the programe. Seems the solution with database is neat.
It may be DBMS platform dependent. but if we use SQL as much as we can, when we tranfere from one platform to another, we only need modify grammer and syntacs, leaving business logic unchanged. I don't have much experience on this, and I guess it may not be a lot of work.

1. we have several POS machines with an application that holds products, customers, sales and so on. Once a week this data is refreshed/sent from/to the server via modem

Eduard, so your application keeps running all the time, and stores all thed data into the memory? Then does it take up huge memory? how about your system crashes? those data are gone or be exported into harddisk?
From my point of view, once a week reading/writing with the bridge is dangeous.
Thank you for your replies. I do agree that behaviors and responsibility are very important in OO design. By Larman's method, we identify all kinds of nouns, i.e. entities first. That's exactly what I do for database design. And in my OO design, I seldom has classes called "User", "Customer", "Company", etc, which tends to appear as tables in database. In constrcat, I have classes called "Processor", "Scheduler", "Examiner", which are neither Actor in in Use Cases nor tables in database.
I do have questions about how to make good designs that better fit for appliations with dtabase.
As the database gets more power, Database can do a lot of jobs as well. For example, I'm involved in a project for PC scheduling. We can either use program to do the scheduling, or let database decide how to schedule a particular session. Seems the second solution is better, because database has all the information for scheduling. So I passed the input to database, and let a stored procedure handle the rest of work. In this sense, database can acts like classes and objects.
Can anyone recommend some design principles? what kind of jobs are done by database, and what done by program? All advice is appreciated.
I've been looking into static modelling these days. Larman's book told us basically nouns can be regarded as concepts, thus designed as objects. I remember when I studied database design, instructors also told me to look at noun for potential tables.
So can we say database design and UML class diagram are using same method? Does all the tables in the database will have a wrapper class in the application?
Thank you for clarification.
Has anyone ever used the "code generation" in UML tools? I am wondering if the generated code does help and save labor. Thanks.
XML@whiz is easier than the real one. but I think it goes in the right direction. It almost covers the whole material, probably with different weights.
I think XML@whiz is good. it's not very like the real one, but it helps you to find out your grey points. then you can focus on those weak areas.