Author Archives: Karl
Message formatting in Java
Whatever kind application you’re working on, you will probably need to create some sort of message more complex than “Hello World!” at some point. Whether it’s a log message, or some text to plonk into your nice UI, you will probably also need to format it in some way to include some variable values, and maybe some embellishments like using the correct words for plural and singular values.
Java provides a number of ways to do this. In this post, we’ll look at a few of them.
Scheduling tasks with Quartz
It’s been some time since I started off in the world of software development, but I have found myself looking for a good way to schedule tasks more than once, and I’m sure you have too. You know the sort. Run this report every third Friday of the month, clean out this table at the end of every day, sacrifice a goat every summer and winter solstice, and so on.
Some tasks can happily run in Cron, provided that your operating system has Cron. However, some tasks require a bit more flexibility than this old workhorse can provide. You may need to run the task in the context of your application, for instance, or your requirements might dictate that the scheduling of certain tasks must be controlled by the users. In the case of a Java application, you might not want to start and stop the JVM every time a small task needs to execute.
Enter Quartz, OpenSymphony’s enterprise job scheduler. This API allows you to schedule tasks within your own application, which means that you’re more or less free to control the scheduling your way. In this post, we’ll look at some of the most basic tools which this API brings to the table.
Staying on top of the (Google) Wave
Google Wave is an awesome tool, but right now I don’t have enough contacts on it to make checking it part of my daily routine. This causes me to miss the occasional activity of those friends who do use it, however rarely. Today I found an interesting wave which had been sleeping in there for the last five days, so I decided to look around and see if there are any notifiers available. The one I picked was Waver, which happens to be free, and works on both Mac and Windows.
Are you using Google Wave? What are your thoughts on it so far? Can you recommend any other desktop clients or notifiers for it?
Revisiting the JavaScript Calendar Control – Part 3
It’s been some time since I started writing this three part series, and it certainly took a while longer to get done than I expected. A busy work schedule does tend to do that, but if it makes anyone feel better, having left the third part hanging did give my conscience a field trip. So let’s do a quick recap and get on with it 
Object Caching in Java with EHCache
In a project I was working on recently, we were building up a web page by loading up its template, content hierarchy and other information dynamically. This is a common setup, and a very flexible one since it allows sweeping changes to be made very easily. Unfortunately, this flexibility comes with a cost; pulling everything through EJB calls can give you a speed not unlike that of a slightly stunned tortoise trying to sprint up a treacle covered hill.
One way of mitigating this problem is to use a Facade pattern to load as much as possible with as few calls as possible. However, this is not always the best approach, especially if most of the content is not likely to change very often. In these cases, it’s preferable to store the content at the end where it’s being used, avoiding the remote call completely.
This can be implemented quickly and easily with a Map, but that would leave us with a lot of work to do when it comes to managing the cached content. For example, what if we wanted to make sure that the cache does not continue to fill up indefinitely, or that it gets backed to disk when it goes idle for some time to preserve memory?
Since we were already using Hibernate in the data layer, we were already using a cache at that level in the form of EHCache. It made sense to try and see if it was possible to use this in our controller layer, and it turned out to be extremely elegant to use. Continue reading