Skip to main content

Static Variables: The wild goose chase ends here.

(Continued from yesterday..)

So we dint know what was copying the instance attributes to other instances. If it was not the Batch Job, There is definitely a non thread safe code that's doing it. But with so many threads, how easy is it to track down the cause. A wild card search for static would result in a lot of static variables in code.

Thank fully, there was a small market tracking method. This method profiled all the requests. And the data collected was stored in DB. so we were able to look at the requests that were *possibly* causing this. From there it was only a matter of debugging the code.

Unfortunately, We didn't find anything statically referring in our code. but we soon realised it was happening in a (our own) library module that employed its own threading pattern. And there was a STATIC transactional variable. The rest of the story is imaginable. Remove the static reference rebuild the lib and deploy it.

But there are important lessons to be learnt here.

Of all the things, Stop declaring static for transactional variables. static - means static - IT should rarely change!! and by definition *common* in nature. If there is a user account object. It can never be static. even if you are using a HOLDER object, it should not be static. Get a clear picture on that.

And then, Stop using Threads in JEE unless you completely know what you are doing. The main reason threads were used here was that they were trying to implement pooling for connections to Mainframe. A better suggestion would be to employ Connection pools in the container. Stop using your own.

Finally, Keep options to profile your application. Once your application goes into production, you have a totally different picture than that of your Dev. Keeping a way to track the application solves a lot of headache and reduces speculation.

Popular posts from this blog

Javascript: Convert Strings to Binary (and representing in a nerdy way!)

I follow those GoogleDevelopers Videos . Sometime back, in one of the presentations on GoogleIO, there was this interesting string of dots at the bottom of each page of the presentation . They looked like random big and small dots. A similar bunch of dots were also on the T-shirt of a presenter was wearing in another presentation . While it seemed something in the pattern, I could not find what it was. Finally, another presenter cleared the matter that those dots are just binary representation of "GOOGLEIO" (So much for advertizing Google IO, Impressive!). So I wanna do it. Takes me back to days of those DSP classes at school. Nerdy me had to churn some old brain cells. I remember those first programming language classes in Pascal and C when you were asked to do fibonacci series and converting a binary string to ascii codes. That *experience* came handy here: Check it out! Text to Binarize: For those who came to copy the javascript code to convert string to binary,

MySql Copying Table Structures.

Some times you need to copy only table structures across databases. This article describes two ways of doing it. If the whole database schema need to be exported, mysqldump is very effective. A --nodata flag will dump all tables' schema. Like this. mysqldump --nodata -p -u username databaseName But if you want to copy a specific table, individually, you could use "create table like" feature. You could create it even from a different database. However it must be on the same mysqld instance. Like this. create table newtable like oldtable; --Or from a table in other database create table mytable like otherdatabase.tablename;

javascript maxlength for textarea with \r\n breaks in java (esp Firefox)

Textareas allow new lines to enter. These are represented by \n (1) or \r\n (2) characters. But when you save to DB you have a limit to certain length of chars. There is no maxlength attribute in HTML that will stop you from entering data. This is generally acomplished by Javascript. You do a onkeyup hook and stop event or trim after textarea.value.length > maxlength. There are many other solutions out there.. But.. Here is the problem that most of those solutions overlook, How do you deal with the count on \n and \r\n representations. Lets first see how it matters. If the text entered has new lines, the length is calculated differently in Firefox and IE. When you enter a Text like 01234 567890 You expect the textarea.value.length to be 11. (10 chars + new line).On the backend, however, java would recieve it as 12 chars (10 chars + \r\n) (this is irrespective of FF or IE). So you are effectively saving 12 chars to DB. Worse yet, IE seems to figure textarea.value.length as 12 (