In a previous post I explained what Kotlin Object Declarations are. This time around it’s about the declaration’s sibling, the Object Expression.
An object is not just a glorified static replacement or a singleton. object can be used where Java usually utilizes anonymous inner classes. Let’s look at a more realistic scenario: a JButton and an ActionListener or a MouseListener.
Instead of implementing my own backup application as I had planned a long time ago, I’m wandering off (re)learning Kotlin after a long absence from that language. In my defense though, I’m doing it in the context of the backup app which will not be Java as originally intended (or maybe later for comparison, who knows, I obviously can’t be trusted with my plans). Putting that aside, the most confusing concept of Kotlin for a Java developer is the object. What is that thing doing that a class can’t do and how do we declare static fields and methods? I know it’s nothing new, but that part seems to have changed a bit since I used Kotlin about two (?) years ago. So, for me this is a refresh of old information and also something new and by writing about it I will engrave it in my brain once and for all. And your confusion will hopefully turn into some productive… fusion… of some sort… or so.
I’ve been a gamer for a very long time – it’s easily been twenty years or more (yes, I’m old). But, in the past year or so, my excitement has been waning. I have mentioned in another blog post that I was planning to replace my big tower PC with a notebook for (mobile) coding and writing – which I have done – and, in the short- to mid-term, get a gaming console to replace the video gaming part of the PC with something more casual and affordable. This day has finally come and the first game I have played has been Red Dead Redemption 2. Now, this game was many firsts for me:
I think Red Dead Redemption is something very special and I will try to explain why I think that is. One thing is for sure and that is the fact that it has rekindled the fire within me to play a video game on-end without pause. Unlike the other game reviews/experience reports I have written so far, this one is a bit different. I started writing when I was about 40% through the game and added to it at different stages of progress. In short: it’s like a diary.
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I ran across this issue only by accident because I was investigating a completely different problem. I wrote a quick test to debug my issue and was wondering why custom serializers and deserializers are not registered with the Jackson ObjectMapper. I had a nice init() function that was annotated with @Before. So, what the hell?
Let’s back up a bit for some context.
I’m used to JUnit 4, so in my test I used @Before to annotate a setup method. It was one of the many options IntelliJ presented to me.
@Before
fun init() {
val module = SimpleModule()
module.addDeserializer(Instant::class.java, InstantDeserializer())
module.addSerializer(Instant::class.java, InstantSerializer())
mapper.registerModule(module)
}
The method wasn’t called, however. But it’s annotated! Well, it’s the wrong annotation if you’re using JUnit 5. The correct one is @BeforeEach. This one and @BeforeClass (new name @BeforeAll) have been changed from version 4 to 5 to make their meaning more obvious.
But that’s besides the point. The question is: where does this @Before come from then?
A look at the dependency tree quickly reveals the culprit.
It’s the official JetBrains Kotlin JUnit test artifact. Although it doesn’t hurt me to have it in my project, it certainly caused some confusion and I’d like to avoid that in the future. Hence, I excluded the old version of JUnit in my POM file for this dependency.
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-test-junit</artifactId>
<version>${kotlin.version}</version>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</exclusion>
</exclusions>
</dependency>
Problem solved.
With the release of the Google Pixel 3a I once again started thinking about what I want in a smartphone. As a reminder, the last time I was pondering the purchase of one I was musing of tall phones, curved displays and notches. I am not in the market for a new phone right now as my iPhone 8 is more than capable of fulfilling my needs. But, with the recent launch of the Pixel 3a I wished that this device had already existed a year ago because it is basically the perfect phone for me. And I also wish Google would get back into the market of less expensive phones with the latest and greatest hardware as was the case with the Nexus line.
Read More »I recently had to deal with this little bugger as we moved from the OpenJDK 8 package supplied by the Linux distro of choice to AdoptOpenJDK 8. It is important to know that we completely uninstalled OpenJDK, including all its transient dependencies.
(And in due time we’ll uninstall Java 8 and replace that grandpa as well)
As a result, parts of our application didn’t work any longer, resulting in this nice and shiny Java stacktrace.
2019-05-03 08:22:07,345 ERROR [qtp1896708863-35] [PlotChartController] [/][/][/]- error while creating chart image
java.lang.NullPointerException
at sun.awt.FontConfiguration.getVersion(FontConfiguration.java:1264)
at sun.awt.FontConfiguration.readFontConfigFile(FontConfiguration.java:219)
at sun.awt.FontConfiguration.init(FontConfiguration.java:107)
at sun.awt.X11FontManager.createFontConfiguration(X11FontManager.java:774)
at sun.font.SunFontManager$2.run(SunFontManager.java:431)
at java.security.AccessController.doPrivileged(Native Method)
at sun.font.SunFontManager.<init>(SunFontManager.java:376)
at sun.awt.FcFontManager.<init>(FcFontManager.java:35)
at sun.awt.X11FontManager.<init>(X11FontManager.java:57)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at java.lang.Class.newInstance(Class.java:442)
at sun.font.FontManagerFactory$1.run(FontManagerFactory.java:83)
at java.security.AccessController.doPrivileged(Native Method)
at sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:74)
at java.awt.Font.getFont2D(Font.java:491)
at java.awt.Font.defaultLineMetrics(Font.java:2176)
at java.awt.Font.getLineMetrics(Font.java:2246)
at org.jfree.chart.axis.DateAxis.estimateMaximumTickLabelWidth(DateAxis.java:1453)
at org.jfree.chart.axis.DateAxis.selectHorizontalAutoTickUnit(DateAxis.java:1365)
at org.jfree.chart.axis.DateAxis.selectAutoTickUnit(DateAxis.java:1340)
at org.jfree.chart.axis.DateAxis.refreshTicksHorizontal(DateAxis.java:1616)
at org.jfree.chart.axis.DateAxis.refreshTicks(DateAxis.java:1556)
at org.jfree.chart.axis.ValueAxis.reserveSpace(ValueAxis.java:807)
at org.jfree.chart.plot.CombinedDomainXYPlot.calculateAxisSpace(CombinedDomainXYPlot.java:364)
at org.jfree.chart.plot.CombinedDomainXYPlot.draw(CombinedDomainXYPlot.java:442)
at org.jfree.chart.JFreeChart.draw(JFreeChart.java:1235)
at org.jfree.chart.JFreeChart.createBufferedImage(JFreeChart.java:1409)
at org.jfree.chart.JFreeChart.createBufferedImage(JFreeChart.java:1389)
at org.jfree.chart.ChartUtilities.writeChartAsPNG(ChartUtilities.java:183)I obviously removed some (a lot) parts to make it more readable and to hide corporate IP 😉 But this is the relevant part.
I found this bug report on Github and for once, plowing through the comments, it helped me. As is mentioned there, the culprit is the missing “fontconfig” package. So, I added another Ansible task to our playbook to provision the server et voila, the problem is gone.
- name: Install fontconfig package
package:
name: fontconfig
state: present
tags:
- java
As mentioned earlier, we had wiped all that was relevant to OpenJDK off the system and by doing so, also uninstalled the “fontconfig” package. Otherwise this error wouldn’t have surfaced. But that’s the benefit of starting with a clean slate. This way you know if something is missing and don’t get surprised by errors all of a sudden while, at the same time, it is working on another machine.
Almost all of the tutorials and blog posts I found on this topic were focused on Spring Boot because, starting with version 2, it uses Micrometer as its metrics framework. However, in a particular project at work we do not have access to Spring Boot let alone a recent Spring version. Therefore, I’m explaining how to include Micrometer in your non-Boot Spring application using XML configuration.
In this tutorial I will be using Spring 5 and Java 11, so not exactly the versions I’m dealing with at work, but the concepts are the same and everything can probably be copied exactly as shown here.
Read More »I’m a person that usually writes tests before the implementation. In the context of my backup application project this has turned out to really slow me down. But it’s not just a problem of my personal projects. It also affects my professional work.
Here’s the issue: for some tests you need test data and generating that test data can be a tedious task, depending on the complexity. This has caused me to procrastinate on my backup app. So, one evening, after having thought about this during a workout, I grabbed my laptop, sat down in my comfy bed and wrote a “DSL” that makes creating the data much simpler. Not only is it easier to create the data now, allowing me to continue at a faster pace, it’s also much more readable and the test setup doesn’t clutter the test case anymore. This is a very important aspect of a test. What good does it to have one if, after some time, you have to update it and don’t understand what it does anymore?
Read More »While I’m actively procrastinating on my backup application and finishing my MacBook Pro review, I was pondering on what tool I should continue to use or start to use for writing my blog posts. I’ve tried a few things in the past, one of them being Markdown in Byword way back in the early stages of my blogging efforts, Libre Office and the ODT file format sometime after that and more recently Microsoft’s Word using its DOCX format. To generalize it a bit:
Both tools have their pro’s and con’s, but none of them are the perfect solution and I’m finding myself doing a bit of this and a bit of that, but never being really satisfied.
Read More »I tend to write a lot of background to paint a picture why I’m doing things, so I’ll try to keep it short for to move on to the code quickly.
I have a digital music collection that was sorted by the first letter of the artist (A, B, C etc.) and then the artist and underneath that the albums. While that is good to find things, it’s not optimal for listening in my car (via USB stick). Sometimes I find myself wanting to listen to all of Melodic Death Metal on shuffle play. My car doesn’t support this like iTunes, with its internal music library, which is why I wanted to group artists and albums by genre. Since I didn’t plan to do this all manually, I opted to write some scripts in Python.
The code is available on GitHub. If you have suggestions for improvements, please comment or create a pull request. I’m not a Python pro, so I’m sure there’s some room to make it better.
Read More »If you are a user of any form of computer and care one bit about your sanity, then you probably have a backup strategy. Otherwise, if all hell breaks loose and your whole computer burns to ash or the hard drive melts to a heap of metal, turning it into an ugly door stop, you’ll likely be kinda angry, maybe slightly pissed, your pulse most definitely at 180, that you’ve lost all your data. I’d certainly be, especially about all my pictures of all the festivals and places I’ve been to.
(And maybe some family 😅)
But, to be honest, I’ve been a bit lazy about backups for some time now. I do have copies of all my important files, but that’s not a backup. It’s a copy. A backup lets you go back in time and get an older version of a file or folder, not just the most recent one that has been synced.
So why is it, that I’m not as diligent as I should be? There are a few factors in that equation. It’s laziness for one, knowledge that I do have at least one copy, the fact that I haven’t had any data loss so far and stinginess. Why the latter? Up until now, being a Windows user (not any more though, on my main machine), I was relying on Acronis True Image, a commercial backup software. However, the version that I own – 2014, I think – stopped being reliable in one of the past Windows 10 versions. I simply don’t want to spend the money any more.
I’m not here to tell you that I have changed my mind on that. No. I’m, of course, coding my own solution. Why wouldn’t I? Everything is done multiple times in the Open Source community.
Read More »In my search for information about what a web.xml exactly is and does, I ran across a video series on YouTube of Dr. Jules White who created over 70 videos explaining the basics and advanced topics of creating web services for mobile applications. The videos are roughly between 5 and 15 minutes long, so they are ideal for in-between watching, without sacrificing in content. You can binge them too, of course.
What I found most pleasing is that his presentation style is very informative and professional. There are no awkward pauses or anything else that would make me cringe. It’s very pleasant to watch and there’s a lot of good information in it, even for someone that already has a background in building web applications.
I created this list of links to all the individual videos because wanted to have more structure and information than a YouTube Playlist can provide in case I want to go back and watch something particular. Additionally, there’s a little sorting and numbering bug in the YouTube Playlist 😉
So, here you (or I) go.
Groovy Spock is a testing framework that can be used as an alternative to the venerable JUnit. In Java projects it’s probably very common (I don’t have any data, just an assumption based on how I think) to also use a Java based testing framework. The most widely known is JUnit, although not the only one of its kind (e.g. see this article on DZone). However, Java’s syntax can sometimes be rather cumbersome and verbose, and this is where a dynamic language like Groovy can help. It is often used to create nice and interesting DSLs, e.g. as the basis of the Gradle project or, as in the case of Spock, for testing.
Here’s how to integrate the Groovy Spock testing framework in a Maven based Java project.
One thing up front: I’m no fan of Groovy. I’ve worked with Grails projects for several years and using Groovy has more than once proven to be a problem. Especially in very large applications. However, I do see the benefits it can provide in certain situations and I have come to like the more expressive, although sometimes odd to read, Spock DSL in tests.
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This is a short opinion piece about a very good talk I’ve been watching recently. It was presented by Kevlin Henney and is about seven ineffective coding habits of many programmers. Not only is his style very engaging and entertaining, it also contains seven informational things a coder might want to think about. While I generally agree with all of it, there’s one instance where I can see why it is done – if that’s the actual reason is a question for another day. I’m talking about appending the word Exception to classes that are exceptions.Read More »
As an avid listener of Windows Weekly I often hear discussions between Paul Thurrott, Mary Joe Foley and Leo Laporte about Microsoft’s Fluent Design. Microsoft continues to evolve the visual language of Windows and thus it’s a regular topic on one of my favorite podcasts. I’ve been noticing it here and there myself, mainly in system dialogs, but I’ve never really paid any attention because none of the applications I use on a regular basis make use of it – and currently I’m rather happy about that fact. Just recently though, I was struck by one effect in particular and that was the spark that got this blog post going. To be honest, in most cases where I notice these Fluent Design elements I think of them as rendering bugs. Like sometimes in games, when the graphics driver is not yet optimized, or a badly programmed game engine draws odd pictures sometimes, flaws in an otherwise normal picture. I have a few examples to show to you.
The Gameslinger 