I blog about my experiences working as a developer, architect. Originally from the UK, currently in Vienna.

These days I mainly work on web software and REST services using Java, Spring, PostgreSQL, AWS and React.

— Adrian Smith

2006

Blogging since

Latest Posts

Git loses untracked files during “stash” if there are conficts

Git functionality has changed (and by “changed” I do not mean “improved”) somewhere between Git 2.24 and Git 2.33. “Stashing” then “unstashing” untracked files (new files you’ve just created) loses those new files, if any of the existing tracked files has a conflict. Let me explain. You’re adding a new feature to your codebase (you’ve made changes to some files, and you’ve added some new files). You see a bug, and want to fix it right away as a separate commit. Read more...

Debian 10 box in Vagrant fails with grub error

If you are trying to get Debian 10 Buster to run in Vagrant and are receiving the following error default: /dev/vda does not exist, so cannot grub-install to it! default: You must correct your GRUB install devices before proceeding: default: default: dpkg-reconfigure grub-pc default: dpkg: error processing package grub-pc (--configure): default: installed grub-pc package post-installation script subprocess returned error exit status 1 default: Errors were encountered while processing: default: grub-pc default: E: Sub-process /usr/bin/dpkg returned an error code (1) Add the following shell command before you do your first “apt-get update”. Read more...

How to determine the hostname for absolute links

Links in web applications can be Relative links like <a href="/foo">, or Absolute links like <a href=“https://www.site.com/foo”>. If you’re writing a web application, relative links are generally the way to go. It’s simpler to move the application to a new domain. In addition, for those counting bytes, relative links are shorter. However, sometimes, absolute links cannot be avoided: If you need to redirect to another page, it was necessary in the past to use absolute URLs. Read more...

On Transitioning from Software Developer to Architect

Around 2003 I changed companies and accepted the title “Software Architect” at the new company. Before that, I’d been working as a developer, then lead developer, then development team lead for a B2C startup. If I had a time machine and could go back in time to give myself advice, this is what I would say. Caveat: Unlike “Software Developer” or “Software Engineer”, pretty much each company has its own definition of what a “Software Architect” is. Read more...

Turning off my server with 1.5k days uptime (Video)

Turning off a great server from Hetzner with over 1.5k days uptime (4.6 years). It needed an OS “dist upgrade” so I suppose a reboot was in order anyway. Such a shame! Read more...

Saving and Loading XML to PostgreSQL via jOOQ

To use XML Java DOM objects with PostgreSQL's XML datatype, do the following. Create your table with the XML datatype: (You now have a table where the x column can be an XML document, or can be null.) CREATE TABLE foo (xml_column XML); Add the following to your Maven dependencies: <dependency> <groupId>com.databasesandlife</groupId> <artifactId>java-common</artifactId> <version>8.13.0</version> </dependency> Thereafter, tell the jOOQ generation process that any PostgreSQL columns of the type XML should be converted to/from Java DOM Element objects thus: Read more...

The “backspace” key on the keyboard should delete the last character you typed

I hate when pressing the “backspace” key on the keyboard a certain number of times doesn’t wipe out that number of previous keystrokes. For example, on Mac, if you press the spacebar twice then press backspace key twice you end up with one space. (As Apple inserts a period when you type space twice, so there are now three characters to delete.) Or on Chrome, when typing in the URL bar, pressing the backspace key removes the auto-suggest, not the character you last typed (unless there isn’t an auto-suggest yet, in which case it does delete the last character you typed). Read more...

Use the “Repeatable Read” Isolation Level on PostgreSQL

The database system like PostgreSQL serves requests from many clients simultaneously. Sometimes multiple simultaneous requests might pertain to the same set of data. Programmers often (wrongly) think about the software they write as if it were the only process using the database. The danger is that often their software is the only piece of software using a particular piece of data, meaning that bugs due to this incorrect mindset often go undetected and are deployed to the live system. Read more...

“Activation” library missing when sending email from Jetty on JDK11 despite library included via Maven

When trying to send an email, using JavaMail, from my application deployed via the Jetty web server in Docker, I kept on getting the following errors: java.lang.NoClassDefFoundError: javax/activation/DataSource Caused by: java.lang.ClassNotFoundException: javax.activation.DataSource OK so with the upgrade from Java 8 to Java 11, due to Java 9 Project Jigsaw, a lot of things have been “removed” from the JVM. (Perhaps “removed” is not quite the right word, but they are inaccessible by default. Read more...

Why is my Java software only using one core, on my multi-core AWS ECS Docker instance?

There is no way to get Java to automatically use find out many cores are available and use them all, on AWS ECS using Docker. You have to specify how many cores you want to use via the -XX:ActiveProcessorCount option. On JDK >= 10, use the following JDK options: -XX:ActiveProcessorCount=2 On JDK >= 8, use the following JDK options: -XX:+UnlockExperimentalVMOptions -XX:ActiveProcessorCount=2 Discussion Having optimized my CPU-bound code to make use of multi-core processors, I was disappointed to deploy the software on AWS's Docker implementation, ECS, while paying for an expensive 8-core server, and see all the work happen in sequence on a single core. Read more...

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