Category Archives: Development
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.
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
Revisiting the JavaScript Calendar Control – Part 2
Following last week’s implementation of the basic shape of the calendar, this week we will add behaviours so that we can pick a date on it.
This post is part of a series of three posts:
- In part 1 we created a jQuery plugin which displays a simple static calendar.
- In part 2 (this post), we will add the facility to pick a date, and to switch the month on display.
- In part 3, we will add some sanity checks, and the ability to display events on given days. Continue reading
Revisiting the JavaScript Calendar Control – Part 1
A few years ago, I wrote a calendar control for a Code Project article. Although I’ve used it myself several times, and despite the fact that people still appear to be using it, I can’t help but cringe every time I look at it again. Every time, the thought that comes to mind is “It could have been so much cleaner in jQuery…”.
Well, the time has come to bite the bullet and see how it can be pulled off again. Rather than going over the whole thing in one go though, we’re going to take it in steps over a number of posts to implement a feature or a group of features, so we can look each in slightly more detail. This is as much for my benefit as everyone else’s. If anyone spots anything weird, inefficient, or badong in these posts, please let me know. I like to think of this as public code review, so, you know. Bring it on.
We can rebuild him – we have the technology
The posts will be divided as follows:
- In part 1 (this post), we will deal with the display of a simple static calendar.
- In part 2, we will add the facility to pick a date, and to switch the month on display.
- In part 3, we will add some sanity checks, and the ability to display events on given days.
And with that, on to the post itself. Continue reading