Evaluate structured code in JasperReports

Friday, 13 January 2012

JasperReports is a library which can be used to fill reports from Java applications or just create simple PDFs. It allows you to not only use static output strings but also Groovy expressions. Sadly, this is restricted to simple expressions that result in a value and don't generate multiple class files at compile time.

For example, you could use the following expression to print different values depending if your document has more or less than 10 pages:

JTextPane with background color

Thursday, 1 December 2011

JTextPane and his ancestors JEditorPane and JTextComponent won't respect the color defined with setBackground(Color) since they display a "styled document" and expect the background color to be defined in the content. You'll always see a white background.

To change the background color (without modifying the content) you have to define attributes for the document:

BTRFS im RAID-1-Modus im praktischen Einsatz

Monday, 14 November 2011

Soeben habe ich die neuen 2TB-Festplatten in den Media-PC eingebaut und mich dazu entschieden, dieses mal dem neuen Linux-Dateisystem btrfs eine Chance zu geben. Im Gegensatz zum klassischen ext beherscht dieses nämlich von Haus aus RAID-Funktionalitäten (Level 0, 1 und 10) sowie Snapshots. Das RAID im Level 1 schützt vor physikalischen Fehlern, die Snapshots - sofern man sie regelmäßig anlegt - vor logischen, wie einem versehentlichen 'rm -rf'.

Java: Model-View-Controller without memory leaks

Friday, 7 October 2011

When doing MVC programming in Java, there is a problem that most people don't know about. I've ignored it myself much too long. The problem is that when you bind a model class to an UI component you will get a giant memory leak.

What happens?

Well, imagine a model class supporting listening for property changes. A simple example might look like this (I extend from PropertyChangeSupport here so that I don't have to delegate all the methods, normally you wouldn't do so, of course):

A generic meta packaging format for linux distributions?

Tuesday, 30 August 2011

I'm doing some end-user support for Linux desktops (family and friends). From a chat with my mother and observation of our trainee I've noticed that what's normal users making the most head pains are the different packaging formats. For example, when you want to download Google Chrome Linux users are confronted with four different options:

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