Dev

UPDATE: It seems that starting with hardware version 2, these switches have an actual web interface. Too sad my ones are version 1. 😢

Frankly, I didn't expect it and I was somewhat disappointed when I found out that the TP-Link TL-SG108E Easy Smart Switch (and its little brother TL-SG105E) cannot be configured via web browser. And I was even more disappointed when I found out that, even though Linux and MacOS were listed on the retail box, the configuration tool Easy Smart Configuration Utility runs on Windows only. And they mean it! When started in a Windows VM, the utility does not see any switches.

So the devices are rather cheap for a smart switch, but they still come with a price: no web interface.

However, thanks to some help in the interwebs, I was finally able to run the Configuration Utility on Fedora Linux. It's not that easy, though.

Sass is a kind of precompiler for CSS that offers additional features like nested styles, variables or includes. The syntax of scss files is similar to standard CSS, so it's very easy to learn.

My goal is to:

• nicely integrate Sass into the Maven build process,
• use Jetty to see the web application with the compiled css files, and
• see changes to a Sass file live (without running Maven or restarting Jetty).

While upgrading my blog software Cilla to Java 8 and Hibernate 4, I found out that the old hibernate3-maven-plugin refused to create schema.sql files. Well, it wasn't really surprising. The name of the plugin already implied that the plugin won't play with the next major release of Hibernate.

I could not spot an official update of the plugin. Instead, I found Kai Moritz new Hibernate 4 maven plugin, which turned out to be very useful.

One key feature is to set up and initialize a local database for unit testing. I don't need this feature for Cilla (yet 😉). All I need is a hbm2ddl style generation of a SQL schema file for setting up new instances of my blog software from scratch. It turned out that the plugin was easily configured that way, and so it got almost a drop-in replacement for the old plugin.

This is what the <plugins> section of the project's pom file looks like:

<plugin>
    <groupId>de.juplo</groupId>
    <artifactId>hibernate4-maven-plugin</artifactId>
    <version>1.0.4</version>
    <executions>
        <execution>
            <goals>
                <goal>export</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <hibernateDialect>org.hibernate.dialect.PostgreSQL82Dialect</hibernateDialect>
        <target>NONE</target>
        <type>CREATE</type>
    </configuration>
</plugin>

With the target set to NONE, the schema.sql file is quietly generated while building the project. If set to SCRIPT, a copy will be dumped to stdout.

A CREATE type only generates create statements of the database. The default is BOTH, which creates drop and create statements.

Since no actual database is created, there is no need to add user, password and url parameters.

A list of all configuration options can be found here. The plugin is available at Maven Central.

The Android Device Monitor is not just an aid for debugging applications, but also allows to simulate GPS positions, so you won’t need to actually run around in the countryside for testing your GPS app. But where to get test data from?

I have recorded some of my hiking trips with my Garmin GPS 60, and saved them in Garmin’s proprietary gdb file format. These files contain waypoints, routes and also recorded tracks.

The Swiss Army Knife for GPS files, gpsbabel, comes in handy for converting a gdb file into the GPX file format that can be read by DDMS. This is the line I used for conversion:

gpsbabel -i gdb -f hike-track.gdb -o gpx,gpxver=1.1 -F hike-track.gpx

Note the gpxver=1.1 option, as DDMS is unable to read GPX 1.0 files.

After converting and loading the GPX file into DDMS, I can now send single waypoints as GPS events to the emulated device. But beyond that, I can also play back a recorded track, and simulate that I carry around the emulated device on that track. This is very useful for testing GPS apps.

Android 4.2.2 comes with a new security feature. If you try to connect to your smartphone via adb and USB debugging, you will note that your device is marked as "offline". Additionally, a dialog shows up on your device, presenting an RSA fingerprint of your computer and asking for confirmation to accept a connection.

The rationale is that if your device is lost or stolen, there is no way to read its content even if USB debugging was enabled.

Now, presenting an RSA fingerprint surely is a nice idea to avoid man-in-the-middle attacks. But how do you get that fingerprint in order to compare it with the one shown on the device? At first I thought there must be a command (or an adb option) that prints out the fingerprint, but I wasn't able to locate one. After spending some time with my favourite search engine, I finally dug up a rather more than less complicated command line that prints out the footprint:

awk '{print $1}' < adbkey.pub | openssl base64 -A -d -a | openssl md5 -c | \
  awk '{print $2}' | tr '[:lower:]' '[:upper:]'

The command must be executed in the directory where adb stores the adb key, which usually is ~/.android (or /root/.android if adb runs as root).

If you are somewhat security paranoid, you surely wonder why, on the one hand, Google shows a footprint on the device, but on the other hand makes it difficult to find out if that footprint actually belongs to your computer.