A little while back I knocked up a post describing how to enable a Spring application to connect to multiple data sources. At the time, I had only just heard about Spring Boot at the SpringOne 2GX conference in Santa Clara, so the examples didn’t take advantage of that and also didn’t work around some of the autowiring that it does.

Recently, I was working on a little ETL project to migrate data from one database to another with a different structure, so I returned to this problem and the following is the result.

Continue reading “Multiple databases with Spring Boot and Spring Data JPA” →

A series of videos has just been posted on YouTube by Mark Proctor. They cover using the new KIE Workbench, which is rather different from previous Guvnor versions.

http://www.youtube.com/watch?v=vj3MNmiUnvY&list=SPb9jQNHBKBRj9IJkc_F5nCJAvXaegOGW8

I haven’t gone through them all yet, so I can’t say much about them, but they look to be a good preview for anyone considering a move to the new KIE Workbench.

Working in the financial industry, I have become rather strict about avoiding doubles in Java. The trouble is that they are a floating point representation of a number, which is just an approximation of the real value. This can lead to some unusual results.

For instance, according to this, 0.34 + 0.01 is not equal to 0.35.

double x = 0.35;
double y = 0.34 + 0.01;
System.out.println(x + " : " + y + " : " + (x == y));
0.35 : 0.35000000000000003 : false

Those inaccuracies might seem very small, but it’s surprisingly easy for them to start impacting a real world application. Imagine you wanted to sell dollars and buy Iranian Rial. You would be getting almost 20,000 Rial for every dollar. At that rate, imprecise floating point values could easily impact the final amount being sent. Although with the current US trade sanctions against Iran, that could be the least of your problems.

Continue reading “A BigDecimal accumulator for Drools” →

Originally posted @ gratiartis.org on April 5th 2008.

When at work, I’m generally in the worlds of Windows and Solaris. But these days I’m doing my home development work on a MacBook Pro. But I’m keen to make sure that I can do everything that I do at work so that I can experiment in my own time. So here’s a list of the software I use to develop on the Mac and where to get it.

Continue reading “Development tools” →

Originally posted @ gratiartis.org on April 5th 2008.

I mentioned my use of the WebLogic Scripting Tool a little while back. I have noticed since then that a number of folks visiting this site are looking for example scripts. I have obviously written a number myself and I promise I’ll try to get around to posting them here. However until I get myself in gear, I thought I would point you at some useful examples that are already out there. I’ll expand this post as I find more…

Continue reading “WebLogic Scripting Tool – Scripts” →

Since I’m now playing around on a MacBook Pro I thought I’d see whether it was possible to get BEA WebLogic running on it. As it turns out it’s quite simple. These instructions seem to apply to anything from 9.0 upwards, but there’s a link to instructions for 8.1 below.

Continue reading “WebLogic on Mac OS X” →

Originally posted @ gratiartis.org on April 16th, 2007.

The financial industry does seem to be loath to share the fruits of their efforts. There doesn’t seem to be a lot around. And certainly not much that is regularly updated. Maybe everyone is worried about sharing trade secrets, but the rules for calculations are well established and I’m guessing that everyone must be writing their own implementations or buying in over-priced modules.

Continue reading “Open source financial libraries for Java” →

Originally posted @ gratiartis.org on April 6 2007

As a developer of financial systems, I’m constantly disappointed by how difficult it is to perform precise decimal arithmetic in Java. It’s fairly common knowledge that the use of double is not much use for financial calculations. As a quick example, take a look at the following piece of code.

public static void main(String arg[]) {
    BigDecimal bd = new BigDecimal("58.99").add(new BigDecimal("0.99"));
    System.out.println("BigDecimal result: " + bd);

    double d = 58.99 + 0.99;
    System.out.println("Double result: " + d);
}

You would have thought both results should be the same. However, you end up with:

BigDecimal result: 59.98
Double result: 59.980000000000004

This is caused by the fact that in Java, operations on double primitive uses floating point arithmetic. The use of floating point arithmetic does make it relatively fast to perform the operations. The approximate nature of them may not matter in all situations, but for financial calculations it can cause all sorts of problems.

Continue reading “Groovy as a financial domain language?” →

Originally posted @ gratiartis.org on February 5th 2007.

According to the BEA documentation, the WebLogic Scripting Tool is a command-line scripting interface that system administrators and operators use to monitor and manage WebLogic Server instances and domains. It allows you to write scripts in Jython that are able to connect to a running WebLogic domain and make modifications to the configuration with no need to restart anything. It can also be used for creating and modifying a domain in its offline mode. It comes as standard with WebLogic 9.2 and a version is available for 8.1. It is recommended and supported by BEA for automating WebLogic server administration. I am currently developing WLST scripts to improve the development and deployment process.

Continue reading “WebLogic Scripting Tool” →

Today, in a rush of organisation, Scattercode Ltd has been incorporated as a limited company.

There are numerous programming languages and frameworks out there, and rather than advocating one true technology, there is much to learn by working with a range of platforms, spotting some of the best ideas, and cross-pollinating those concepts.