kenneho.net

Alarm clock for kids

August 16, 2016 Kenneth Holter Comments 0 Comment

I’ve created a very simple Raspberry Pi project that I use to let my kid know if its daytime or nighttime. When I say goodnight and leave my kids bedroom, I trigger a simple script on my Raspberry Pi with a 7″ touchscreen attached. The screen will display a daytime image for a few minutes, before switching to a nighttime image. The nighttime image is an indication for my kid to put down her toys and go to bed. Over…

Using the “Oboe” Javascript library to speed up data processing

February 13, 2016 Kenneth Holter Comments 0 Comment

One of our node.js applications at work was designed to call an internal rest service, cache the whole response, and iterate over the data to separate relevant data from non-relevant data, and write the relevant data to file. To speed things up a bit, we wanted to process, filter and write the data to file as it arrived. For this task, the excellent Javascript library “Oboe” came in handy:

var oboe = require('oboe');

var fs = require('fs');

var jsonFileStream = fs.createWriteStream('myfile.json')[...]
var acceptHeader = {
    Accept: 'application/json'
}
var requestHeader = {
    url: "http://rest.example.local/myapp",
    headers: acceptHeader
}
oboe(requestHeader)
    .node('{ref hostname}', function(item) {
        handleItem(node, write_item_to_file);
    })
    .done(function() {
        jsonFileStream.end();
    });

function handleItem(item, callback) {
    if (isInterestingData(item)) {
        callback(item);
    }
}

function isInterestingData(item) {...}

function write_item_to_file(item) {...}

var oboe = require('oboe');

var fs = require('fs');

var jsonFileStream = fs.createWriteStream('myfile.json')[...]

var acceptHeader = {

Accept: 'application/json'

}

var requestHeader = {

url: "http://rest.example.local/myapp",

headers: acceptHeader

}

oboe(requestHeader)

.node('{ref hostname}', function(item) {

handleItem(node, write_item_to_file);

})

.done(function() {

jsonFileStream.end();

});

function handleItem(item, callback) {

if (isInterestingData(item)) {

callback(item);

}

function isInterestingData(item) {...}

function write_item_to_file(item) {...}

Keywords: HTTP response streaming

Using Maven to build and run Java applications

March 10, 2015 Kenneth Holter Comments 0 Comment

Say you want to have Maven handle the dependencies for your java application containing the well known “public static void main” method. Create a Maven project, put your MyApplication.java file under the “src”-folder, and add something like this to you pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<build>
   <sourceDirectory>src</sourceDirectory>
   <resources>
      <resource>
         <directory>src</directory>
         <excludes>
            <exclude>**/*.java</exclude>
         </excludes>
      </resource>
   </resources>
   <plugins>
      <plugin>
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.1</version>
         <configuration>
            <source>1.7</source>
            <target>1.7</target>
         </configuration>
      </plugin>
      <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>exec-maven-plugin</artifactId>
         <version>1.3.2</version>
         <executions>
            <execution>
               <goals>
                  <goal>java</goal>
               </goals>
            </execution>
         </executions>
         <configuration>
            <includePluginDependencies>true</includePluginDependencies>
            <executable>java</executable>
            <mainClass>MyApplication</mainClass>
         </configuration>
      </plugin>
   </plugins>
</build>

<?xml version="1.0" encoding="UTF-8"?>

<build>

</excludes>

</resource>

</resources>

<artifactId>maven-compiler-plugin</artifactId>

</configuration>

</plugin>

<groupId>org.codehaus.mojo</groupId>

<artifactId>exec-maven-plugin</artifactId>

<goals>

</goals>

</execution>

</executions>

<mainClass>MyApplication</mainClass>

</configuration>

</plugin>

</plugins>

</build>

Now you can run your application using the exec-maven-plugin, like this:

mvn clean compile exec:java -Dexec.args="arg1 arg2 arg3"

1	mvn clean compile exec:java -Dexec.args="arg1 arg2 arg3"

“Løp til bussen” – Android-app’en som forteller deg om bussen din er forsinket

January 25, 2015 Kenneth Holter Comments 0 Comment

For å lære meg litt om Android-programmering jeg har laget en enkel app. App’en er svært enkel, og har som eneste formål å vise sanntidsinfo for din neste reise med buss, bane, tog, trikk eller båt. Utgangspunktet mitt var at jeg enkelt ønsket å finne ut om jeg måtte løpe til bussen eller ikke, for jeg har altfor mange ganger løpt til bussen tidlig om morgenn, for så å bli stående å vente på den fordi den er forsinket.

Simple script for dumping a MySQL database

October 20, 2014 Kenneth Holter Comments 0 Comment

As file system backups might fail to backup open files, it’s good practice to close any open files before running the backup. Closing a MySQL database file means you will have to stop the MySQL server itself, causing causing a database outage while the backup is running. But fortunately there’s a smarter way to backup you database – simple dump the entire database to a file (which is automatically closed when the dump is completed), and have your file system…

Setting up Sublime Text as a node.js development environment

August 21, 2014 Kenneth Holter Comments 0 Comment

Sublime Text makes a great IDE for node.js development. First, install the node.js software and get your initial project up and running. Various tutorials on the web should get you going. When it’s time to run your app, configure the Sublime Text build system to build it and run it. To avoid having to start and stop your Node server manually, make use of the tool Nodemon – this tool will build and run your app automatically when you edit…

How to view the contents of your WordPress database

December 11, 2012 Kenneth Holter Comments 0 Comment

My site is running WordPress, which store data in a mysql database. As part of my backup procedure, I backup the database as well as the WordPress files. For fun I thought I’d inspect the actual contents of the database, and in case others wish to do the same here’s how to go about it.