Mechanical Bird Song Device from 1890

High-Speed Robot Hand

Unit Testing Runtime Exceptions with JUnit4 and Hamcrest

Junit and Hamcrest make unit testing with Java almost enjoyable. In this post, I show how to unit test Exceptions with JUnit4 and Hamcrest. In this over-simplified example, I'm testing a method that always throws an IllegalArgumentException. In real-life the IllegalArgumentException would only be thrown under special circumstances given certain arguments, and those are the ones you want to test with the unit test.

The basic idea is to surround the method you want to test with a try catch block and pass it an argument that will trigger the IllegalArgumentException to be thrown. The fail method call should never be reached, and if it does the unit test should fail. What should happen is that the IllegalArgumentException is caught, followed by a check for the correct message.

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.junit.Assert.fail;

import org.junit.Test;

/**
 * The following example code demonstrates how to unit test Exceptions with JUnit and Hamcrest
 */
public class ExceptionUnitTesting {

  @Test
  public void test() {

    try {
      blah("asdf");
      fail("Expected exception");
    } catch (IllegalArgumentException e) {
      assertThat(e.getMessage(), is(equalTo("Argument foo is not valid!")));
    }
  }

  /**
   * @param foo
   * @throws IllegalArgumentException - in this test case always
   */
  private void blah(String foo) {

    throw new IllegalArgumentException("Argument foo is not valid!");
  }
}

Piece of Cake!!!

Import a Maven Git Project Into Eclipse

The Easy Way

Prerequisites
Install M2Eclipse

Step 1: Clone or create Git Repo. First, you need to clone a Git repo into an empty folder in your workspace. You need to use a Git client such as SourceTree or TortoiseGit for this. Create you workspace first if it isn't already, and clone the git repo directly into a new folder labeled with the project name.

Step 2: Import Into Eclipse. In the Package Explorer view, right-click and choose Import... In the wizard choose Maven -> "Existing Maven Projects" as the project type. Search for the project home directory and click though the wizard.

The Hard Way

Prerequisites
Install M2Eclipse
Install egit

Step 1: Right-click in the Package Explorer area and select Import..., select Maven -> Check out Maven Projects from SCM, and click Next.

Step 2: Choose "git" as the SCM connector next to "SCM URL:" and type in the Git repo URL. If there are no connectors to choose from you have to first install that Eclipse plugin. To do that, click on the "m2e Marketplace" link in the lower right hand corner of the dialog box.

Step 3: Check m2e-egit and click Finish.

Step 4: Select "git" as the SCM connector and type in the Git repo URL.

Step 5: After asking you for the passphrase for ssh access to the Git repo, it will download and import the Java project as a Maven project into your workspace.

Piece of Cake!!!

Bird Brains

Bacteria as a Superorganism

Good Overview of Superstring Theory

What Is Life Really?

Avoiding Name Collisions When Organizing Imports in Eclipse

Is there any way to get Eclipse to automatically give preference to a preferred import when organizing imports? Thankfully, the answer is yes.

For example, I'd like to be able to write:

List myList = new ArrayList();

hit Ctrl + Shift + O and have Eclipse add:

import java.util.List;

And not always ask me which List I want to import:

To tell Eclipse not to ever consider java.awt.List, for example, go to Preferences --> Java --> Appearance --> Type Filters menu. Click add and enter Types you do not want Eclipse to consider for automatic insertion of import statements.

Piece of Cake!!!

XChange - Open Source Java API for MtGox Bitcoin Exchange

UPDATE March 9, 2013: Version 1.5.0 released. Support for 10 exchanges.

UPDATE Jan 31, 2013: Version 1.4.0 released. Support for Canadian Virtual Exchange. Mostly bug fixes.

UPDATE Jan 16, 2013: Version 1.3.0 released. Support for many more exchanges. See release notes and also XChange Release 1.3.0 Announcement

UPDATE Oct 11, 2012: Version 1.2.0 released. Support for Canadian Virtual Exchange.

Supported Exchanges

Together with other members from the Bitcoin community, I've recently created a new open source Java library called XChange. XChange is a Java library providing a simple and consistent API for interacting with a diverse set of financial security exchanges including Bitcoin. The first exchange implemented is the world's largest Bitcoin exchange - Mt Gox. The plan is to add more Bitcoin exchanges and other traditional financial exchanges offerring trading APIs such as Interactive Brokers.

As of the most recent release 1.1.0, Xchange offers the following functionality:

• Support for MtGox Bitcoin Exchange (public) polling market data (ticker, depth, trades, etc.)
• Support for MtGox Bitcoin Exchange (private) polling trade data (account info, market order, limit order, cancel order open orders, etc.)
• Support for MtGox Bitcoin Exchange (public) streaming market (ticker)

Next up on the todo list is:

• Support for MtGox Bitcoin Exchange (public) streaming market (depth, trades, etc.)
• Support for MtGox Bitcoin Exchange (private) streaming trade data (account info, market order, limit order, cancel order open orders, etc.)

Relevant Links

Project Home - http://xeiam.com/xchange.jsp
Code on Github - https://github.com/timmolter/XChange
Example Code - http://xeiam.com/xchange_examplecode.jsp

Examples

The following examples demonstrate getting Ticker data from MtGox, first using the polling API, and second using the streaming API.

Ticker via Polling API

package com.xeiam.xchange.examples.mtgox.v1.polling;

import com.xeiam.xchange.Currencies;
import com.xeiam.xchange.Exchange;
import com.xeiam.xchange.ExchangeFactory;
import com.xeiam.xchange.dto.marketdata.Ticker;
import com.xeiam.xchange.service.marketdata.polling.PollingMarketDataService;

/**
 * Test requesting polling Ticker at MtGox
 */
public class TickerDemo {

  private static PollingMarketDataService marketDataService;

  public static void main(String[] args) {

    // Use the factory to get the version 1 MtGox exchange API using default settings
    Exchange mtGox = ExchangeFactory.INSTANCE.createExchange("com.xeiam.xchange.mtgox.v1.MtGoxExchange");

    // Interested in the public polling market data feed (no authentication)
    marketDataService = mtGox.getPollingMarketDataService();

    // Get the latest ticker data showing BTC to USD
    Ticker ticker = marketDataService.getTicker(Currencies.BTC, Currencies.USD);
    double value = ticker.getLast().getAmount().doubleValue();
    String currency = ticker.getLast().getCurrencyUnit().toString();
    System.out.println("Last: " + currency + "-" + value);

    System.out.println("Last: " + ticker.getLast().toString());
    System.out.println("Bid: " + ticker.getBid().toString());
    System.out.println("Ask: " + ticker.getAsk().toString());

    // Get the latest ticker data showing BTC to EUR
    ticker = marketDataService.getTicker(Currencies.BTC, Currencies.EUR);
    System.out.println("Last: " + ticker.getLast().toString());
    System.out.println("Bid: " + ticker.getBid().toString());
    System.out.println("Ask: " + ticker.getAsk().toString());

    // Get the latest ticker data showing BTC to GBP
    ticker = marketDataService.getTicker(Currencies.BTC, Currencies.GBP);
    System.out.println("Last: " + ticker.getLast().toString());
    System.out.println("Bid: " + ticker.getBid().toString());
    System.out.println("Ask: " + ticker.getAsk().toString());

  }

}

Result:

Last: USD-5.14739
Last: USD 5.14739
Bid: USD 5.12011
Ask: USD 5.1299

Last: EUR 4.07
Bid: EUR 4.0527
Ask: EUR 4.07

Last: GBP 3.3452
Bid: GBP 3.3
Ask: GBP 3.34091

Ticker via Streaming API

package com.xeiam.xchange.examples.mtgox.v1.streaming;

import java.util.concurrent.BlockingQueue;

import com.xeiam.xchange.Currencies;
import com.xeiam.xchange.Exchange;
import com.xeiam.xchange.dto.marketdata.Ticker;
import com.xeiam.xchange.mtgox.v1.MtGoxExchange;
import com.xeiam.xchange.service.marketdata.streaming.StreamingMarketDataService;

/**
 * Test requesting streaming Ticker at MtGox
 */
public class TickerDemo {

  public static void main(String[] args) {

    TickerDemo tickerDemo = new TickerDemo();
    tickerDemo.start();
  }

  private void start() {

    // Use the default MtGox settings
    Exchange mtGox = MtGoxExchange.newInstance();

    // Interested in the public streaming market data feed (no authentication)
    StreamingMarketDataService streamingMarketDataService = mtGox.getStreamingMarketDataService();

    // Get blocking queue that receives streaming ticker data
    BlockingQueue tickerQueue = streamingMarketDataService.requestTicker(Currencies.BTC, Currencies.USD);

    // take streaming ticker data from the queue and do something with it
    while (true) {
      try {
        // Put your ticker event handling code here
        doSomething(tickerQueue.take());
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
  }

  /**
   * Do something fun with the streaming data!
   * 
   * @param ticker
   */
  private void doSomething(Ticker ticker) {

    System.out.println(ticker.toString());
  }

}

Result:

Ticker [timestamp=2012-08-26T20:09:13.202Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3078691906206]
Ticker [timestamp=2012-08-26T20:09:18.651Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:19.568Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:23.152Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:23.975Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:24.790Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:25.205Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:26.018Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]
Ticker [timestamp=2012-08-26T20:09:26.543Z, last=USD 10.6, bid=USD 10.55248, ask=USD 10.6, tradableIdentifier=BTC, volume=3068691906206]

Piece of Cake!!!

Running Average and Running Standard Deviation in Java

Today I needed to generate statistics for a simulation in real-time, which forced me to code a class that calculates the running average and running standard deviation of incoming data. I remember doing this a long time ago for another project based on MATLAB, but today I needed a Java implementation. The following code example shows how to calculate the running average and running standard deviation for streaming data. Thanks to Subluminal Messages for the simple math implementation!

The Code

public class RunningStatDemo {

  public static void main(String[] args) {

    RunningStatDemo rsd = new RunningStatDemo();
    rsd.go();
  }

  private void go() {

    RunningStat rs = new RunningStat();
    rs.put(1);
    System.out.println("ave: " + rs.getAverage());
    System.out.println("std: " + rs.getStandardDeviation());

    rs.put(1);
    System.out.println("ave: " + rs.getAverage());
    System.out.println("std: " + rs.getStandardDeviation());

    rs.put(10);
    System.out.println("ave: " + rs.getAverage());
    System.out.println("std: " + rs.getStandardDeviation());

    rs.put(20);
    System.out.println("ave: " + rs.getAverage());
    System.out.println("std: " + rs.getStandardDeviation());

    rs.put(50);
    System.out.println("ave: " + rs.getAverage());
    System.out.println("std: " + rs.getStandardDeviation());

    rs.put(50);
    System.out.println("ave: " + rs.getAverage());
    System.out.println("std: " + rs.getStandardDeviation());
  }

  public class RunningStat {

    private int count = 0;
    private double average = 0.0;
    private double pwrSumAvg = 0.0;
    private double stdDev = 0.0;

    /**
     * Incoming new values used to calculate the running statistics
     * 
     * @param value
     */
    public void put(double value) {

      count++;
      average += (value - average) / count;
      pwrSumAvg += (value * value - pwrSumAvg) / count;
      stdDev = Math.sqrt((pwrSumAvg * count - count * average * average) / (count - 1));

    }

    public double getAverage() {

      return average;
    }

    public double getStandardDeviation() {

      return Double.isNaN(stdDev) ? 0.0 : stdDev;
    }

  }

}

Results

ave: 1.0
std: 0.0
ave: 1.0
std: 0.0
ave: 4.0
std: 5.196152422706632
ave: 8.0
std: 9.055385138137417
ave: 16.4
std: 20.354360712142253
ave: 22.0
std: 22.794736234490628

Piece of Cake!!!

Create Javadocs for a Multi-Module Maven Project

In this tutorial, I show how to create Javadocs for a multi-module Maven project. Creation of Javadocs requires the use of the Maven maven-javadoc-plugin plugin and running "mvn javadoc:aggregate" on the parent pom.xml. For the sake of this tutorial, I'm taking some excerpts from one of my current Open Source Projects - XChange.

Relevant Links

XChange on Github - To see an actual working example
Javadocs for XChange on xeiam.com - To see what the generated Javadocs look like.

How To

Step 1: Add the following to the parent pom.xml file:

<build>
  <pluginmanagement>
    <plugin>
      <groupid>org.apache.maven.plugins</groupId>
      <artifactid>maven-javadoc-plugin</artifactId>
      <version>2.8.1</version>
    </plugin>
  </pluginManagement>
  <plugins>
    <plugin>
      <groupid>org.apache.maven.plugins</groupId>
      <artifactid>maven-javadoc-plugin</artifactId>
    </plugin>
  </plugins>
</build>

Step 2: Run the following mvn command:

mvn javadoc:aggregate

Piece of Cake!!!

See also: Maven Project Compiles in Eclipse but Maven Build Fails
See also: Using Maven Offline
See also: Hello World - Maven, M2Eclipse and Eclipse

Java XChart Library Now Supports Error Bars

XChart provides a super light-weight and dependency-free charting API for Java. It is open source, hosted on Github, and is licensed with an Apache 2.0 license. I created it over a year ago because I was looking for and couldn't find an easy-to-use plotting library for Java that was similar to the MATLAB's charting tool. I tried JFreeChart of course, but I found that the learning curve was very steep. Like MATLAB's charting functions, I just wanted to simply pass my data to an API, and after a few lines of code, have a plot.

I just recently added support in XChart for making plots with error bars, which is what this post is about. The following demo, shows how to add error bars to an XChart chart. BTW, if you have any feature requests for XChart, please feel free to open a new issue on Github here. For more XChart exmaples go here.

XChart - Open Source Charting API

To use XChart, you first need to get the XChart jar, which is available here. If you use Maven, just add the following to your dependencies in pom.xml:

<dependency>
  <groupId>com.xeiam</groupId>
  <artifactId>xchart</artifactId>
  <version>1.1.0</version>
</dependency>

The XChart artifacts are currently hosted on the Xeiam Nexus repository here:

<repositories>
  <repository>
    <id>xchange-release</id>
    <releases/>
    <url>http://nexus.xeiam.com/content/repositories/releases</url>
  </repository>
  <repository>
    <id>xchange-snapshot</id>
    <snapshots/>
    <url>http://nexus.xeiam.com/content/repositories/snapshots/</url>
  </repository>
</repositories>

Error Bars Example Code

package com.xeiam.xchart.example;

import java.util.ArrayList;
import java.util.Collection;

import com.xeiam.xchart.Chart;
import com.xeiam.xchart.series.Series;
import com.xeiam.xchart.series.SeriesColor;
import com.xeiam.xchart.series.SeriesLineStyle;
import com.xeiam.xchart.series.SeriesMarker;
import com.xeiam.xchart.swing.SwingWrapper;

/**
 * Create a Chart with error bars
 * 
 * @author timmolter
 */
public class Example8 {

  public static void main(String[] args) {

    // generates data
    int size = 10;
    Collection xData1 = new ArrayList();
    Collection yData1 = new ArrayList();
    Collection errorBars = new ArrayList();
    for (int i = 0; i <= size; i++) {
      xData1.add(i);
      yData1.add(10 * Math.exp(-i));
      errorBars.add(Math.random() + .3);
    }

    // Create Chart
    Chart chart = new Chart(600, 400);

    // Customize Chart
    chart.setChartTitleVisible(false);
    chart.setChartLegendVisible(false);
    chart.setAxisTitlesVisible(false);

    // Series 1
    Series series1 = chart.addSeries("10^(-x)", xData1, yData1, errorBars);
    series1.setLineColor(SeriesColor.PURPLE);
    series1.setLineStyle(SeriesLineStyle.DASH_DASH);
    series1.setMarkerColor(SeriesColor.GREEN);
    series1.setMarker(SeriesMarker.SQUARE);

    new SwingWrapper(chart).displayChart();
  }

}

Resulting Plot

Piece of Cake!!! See also: Java Web Apps - Integrating Charts into a Servlet

Jeff Hawkins on Brain Science

To Infinity and Beyond

Richard Feynman - The Pleasure Of Finding Things Out

Curiosity Rover Lands Successfully on Mars!

Bergmolch

Oberstdorf, Germany (June 2012)
Wikipedia Aricle

Schwarzer Rüsselkäfer - Otiorhynchus coecus

Oberstdorf, Germany (June 2012)
Wikipedia Aricle

Ultra Slow Motion Video of Saw Blade Cutting Steel

Alpine Tubifex Worms

Yesterday, while my cousin and I were hiking in the German alps, we stumbled upon some very bizarre creatures in a small permanent puddle in a cow pasture at around 1500m above sea level. What we at first saw was what looked like a colony of tiny red things undulating together and anchored to the silty bottom of the puddle.




After poking the moving red mat, it quickly receded and disappeared under the surface leaving little holes.







Here's what the red things turned out to be - little red worms.



After taking pictures and doing some online research at home, we determined that they must have been Tubifex worms. Here are the links to the German and English Wikipedia pages.

Load a logback.xml Configuration File Programmatically

Today I had a unique situation where I needed to load a logback.xml file programmatically for Logback logging rather than via the standard "from the classpath" way, and here's how I did it. It was quite simple.

The following snippet shows how to load a logging configuration file such as logback.xml programmatically:

LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();
try {

  JoranConfigurator configurator = new JoranConfigurator();
  configurator.setContext(context);
  configurator.doConfigure(logFilePath); // loads logback file
} catch (JoranException je) {
  // StatusPrinter will handle this
} catch (Exception ex) {

  ex.printStackTrace(); // Just in case, so we see a stacktrace

}
StatusPrinter.printInCaseOfErrorsOrWarnings(context); // Internal status data is printed in case of warnings or errors.

Piece of Cake!!

Delete a Branch on GitHub

Deleting a branch on Github or any remote Git repository is very simple and just requires running the following Git command:

git push REMOTENAME :BRANCHNAME

Piece of Cake!!!

Maven Project Compiles in Eclipse but Maven Build Fails

Today I ran into a perplexing Eclipse/Maven issue where my Maven project would compile just fine according to Eclipse, but the Maven compile goal would fail. If you are reading this you probably had the same issue and this might help.

Version Information

Maven 3.0.4
Eclipse Indigo

The Error

The following error was produced by the Maven compile goal:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project blah: Compilation failure: Compilation failure:
[ERROR] Blah.java:[6,17] error: package javax.jnlp does not exist

The Solution

The problem was caused by the scope I had defined for the jnlp-api dependency in a child module in a multi-module Maven project. In the parent module inside the distributionManagement tag in the pom.xml, I defined the scope as "provided". The problem occurred when I accidentally defined the scope for that dependency in the child's pom.xml as "runtime". The fix was of course to make the scopes match in both pom.xml files.

I could have saved a lot more time debugging this, if Maven would have produced a more specific error message. Oh well.

Introductory Maven and m2eclipse Videos

Using Maven Offline

Here's another micro blog intended to help other programmers avoid a very frustrating day of trying to get Maven to work offline. I've only been using Maven for a few months, and today was the first day I worked from home, away from the office, on a new Maven project. I had my laptop with me and assumed I could just tell Maven to work offline out of my local repository. Sounds simple right? I have all the jars I need right here on my local machine. Well, what should have been straight forward was a nightmare, which in the end is very silly and Maven COULD have made this much easier to debug. Hopefully in the next release they will consider improving their error messages.

Version Information

Maven 3.0.4

The Problem

To run Maven offline, you need to use the -o argument or set offline to true in settings.xml. I assumed that would be all that's necessary, but I kept getting the following errors for third-party jars that I added to our Nexus repo at work:

Failure to find blah in http://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced -> [Help 1]

Failed to execute goal on project blah : Could not resolve dependencies for project

The following artifacts could not be resolved

[WARNING] The POM for blah is missing, no dependency information available

The repository system is offline but the artifact blah is not available in the local repository.

The Reason

After an entire day of tracking down the problem online, I finally stumbled upon the reason for all the issues described in these three articles.

One
Two
Three

To quote the first one:

"Thank you. That was the problem. I had had a setting.xml that pointed to
an internal repo at my company, and then cleared it out. Maven puts a
file named _maven.repositories in with the jar file in the local repo
that keeps track of where the jar came from. If the remote repo isn't
available, the build fails. Deleting _maven.repositories solved the
problem.

This seems like an extrordinarily bad design. If a remote system goes
down, you can't do a build? If you have an internal repo at work, and
you take your laptop home, you can't do a build?"

The Solution

Delete all _maven.repositories files in your local repository. Once I did that, the build worked like it should. There's arguably a good reason for Maven to use these files, but it's pretty weak that Maven couldn't improve the error message for this situation. Please go to the Jira Issue Page for this and upvote this.

Install Sonatype Nexus as Windows Service

The following mini-guide takes you through the steps I used to install a Nexus server on a Windows machine.

Step 1: Download and unzip nexus.

Step 2: Move the folder "nexus-2.0.4-1-bundle" to C:\Program Files.

Step 3: Install the nexus Windows Service. Double click the batch file: C:\Program Files (x86)\nexus-2.0.4-1-bundle\nexus-2.0.4-1\bin\jsw\windows-x86-32\install-nexus.bat.

Step 4: Open up Windows Services and start "nexus".

Step 5: Verify it's working. Open up a browser and go to http://localhost:8081/nexus. Login using the nexus default username and password of admin/admin123.

Piece of Cake!!!

Install Sonar Using Oracle as the Database

This short tutorial shows how to setup Sonar with an Oracle 10g database. These instructions and screenshots are

Step 1: Configure Sonar. Open up C:\Program Files\sonar-3.0\conf\sonar.properties

comment out:

sonar.jdbc.url: jdbc:derby://localhost:1527/sonar;create=true

remove comment:

sonar.jdbc.url: jdbc:oracle:thin:@localhost/XE
sonar.jdbc.driverClassName: oracle.jdbc.OracleDriver
sonar.jdbc.validationQuery: select 1 from dual

Step 2: Create database user. Open up SQL*Plus and run the following commands at the prompt:

connect username/password

CREATE USER sonar IDENTIFIED BY sonar;

GRANT UNLIMITED TABLESPACE, CONNECT, RESOURCE, CREATE SESSION, CREATE TABLE, CREATE VIEW, CREATE SYNONYM, CREATE SEQUENCE, CREATE PROCEDURE, CREATE TRIGGER TO sonar;

EXIT

Step 3: Get the oracle jdbc driver. Download ojdbc6.jar from Oracle's download site and place it in C:\Program Files\sonar-3.0\extensions\jdbc-driver\oracle.

Step 4: Restart Sonar.

Step 5: Verify it's running. Open up a browser and go to: http://localhost:9000/. You should see the following...

Viewing the Sonar System Info should reveal that Sonar is indeed running with Oracle:

Piece of Cake!!!

Relevant Links

SQL*Plus on Wikipedia

Steve Jobs Inspires

Install Sonar on Windows as a Windows Service

This short tutorial shows how to setup Sonar as a Windows Service on Windows.

Step 1: Download Sonar from the Sonar download website.

Step 2: Unzip the .zip file and move the entire 'sonar-3.0' directory to 'C:\Program Files'.

Step 3: Double-click C:\Program Files\sonar-3.0\bin\windows-x86-64\StartSonar.bat to start Sonar. If your machine is 32-bit, run C:\Program Files\sonar-3.0\bin\windows-x86-32\StartSonar.bat instead.

Step 4: Verify it's running. Open up a browser and go to: http://localhost:9000/. You should see the following...

Step 5: Setup Sonar to start as a Windows Service. Double-click C:\Program Files\sonar-3.0\bin\windows-x86-64\InstallNTService.bat. If your machine is 32-bit, run C:\Program Files\sonar-3.0\bin\windows-x86-32\InstallNTService.bat instead.

Step 6: Restart the computer.

Step 7: Verify again that it's running. The Sonar Windows service should start Sonar when the machine boots up. Open up a browser and go to: http://localhost:9000/. For administration features, the Sonar default login/password is admin/admin.

One Small Issue

After restarting the computer and checking if Sonar was running, Sonar was not running. After some digging, I found that you can look in C:\Program Files\sonar-3.0\logs\sonar.log to debug Sonar. The following log messages hinted at the problem:

INFO | jvm 1 | 2012/05/02 12:55:26 | WrapperSimpleApp: Encountered an error running main: java.lang.IllegalStateException: Unable to create file in temporary directory, please check existence of it and permissions: C:\Windows\system32\config\systemprofile\AppData\Local\Temp\
INFO | jvm 1 | 2012/05/02 12:55:26 | java.lang.IllegalStateException: Unable to create file in temporary directory, please check existence of it and permissions: C:\Windows\system32\config\systemprofile\AppData\Local\Temp\
INFO | jvm 1 | 2012/05/02 12:55:26 | at org.sonar.application.StartServer.canCreateTemporaryFiles(StartServer.java:60)

Apparently, Sonar is trying to write to a temp file and Windows is not letting it. After all failed attemps to create the Temp folder manually and remove the write protection, I ended up solving the issue by manually configuring the Windows Service. The Sonar Windows Service's "user" was LocalSystem by default. I had to switch the service over to run under a regular user, and that fixed the issue.

Piece of Cake!!!

Relevant Links

Sonar on Wikipedia
sonarsource.org

Continuous Integration Using Jenkins, Git, and Maven

This tutorial demonstrates how to set up Jenkins, Git, and Maven to work together and provide a smooth continuous integration system. While the examples shown here are on a Windows machine, the concepts are the same for other operating systems such as Linux or Mac OS X, and with slight adjustments, can be adapted accordingly. This article assumes the following is installed and running on the system:

• Jenkins (install tutorial)
• Git (install tutorial)
• Maven (install tutorial)

Why CI?

Continuous integration attempts to automate building and testing of source code at regular intervals in order to alert a team as early as possible about problems and merging issues.

From Wikipedia: Continuous Integration, "In software engineering, continuous integration (CI) implements continuous processes of applying quality control — small pieces of effort, applied frequently. Continuous integration aims to improve the quality of software, and to reduce the time taken to deliver it, by replacing the traditional practice of applying quality control after completing all development."

From Martin Fowler: "Continuous Integration is a software development practice where members of a team integrate their work frequently, usually each person integrates at least daily - leading to multiple integrations per day. Each integration is verified by an automated build (including test) to detect integration errors as quickly as possible. Many teams find that this approach leads to significantly reduced integration problems and allows a team to develop cohesive software more rapidly."

Configure Jenkins

Step 1: Enable security. From the Jenkins dashboard, navigate to 'Manage Jenkins' and then 'Configure System'. Note: Newer versions have this under "Configure Global Security" instead.

1.a. Check 'Enable security'

1.b. Choose 'Jenkins's own user database'

1.c. Uncheck 'Allow users to sign up'

1.d. Choose 'Matrix-based security'

1.e. Enter an admin username next to 'User/group to add:'

1.f. Check all rights for the user.

1.g. Click 'Save'

1.h. Enter log in information for the admin user in the form that appears.

Step 2: Add a JDK. From the Jenkins dashboard, navigate to 'Manage Jenkins' and then 'Configure System'.

2.a. Click 'Add JDK' and enter Name and JAVA_HOME.

2.b. Click 'Apply'

Step 3: Add Maven information.

3.a. Click 'Add Maven' and enter Name and MAVEN_HOME.

3.c. Click 'Save'

Step 4: Add Git information.

4.a. From the Jenkins dashboard, navigate to 'Manage Jenkins' and then 'Manage Plugins'.

4.b Click on the 'Available' tab and search using the browser (CTRL+F) for 'git plugin'.

4.c. Check 'Git Plugin' and click 'Download now and install after restart'. The install can take a while.

4.d. From the Jenkins dashboard, navigate to 'Manage Jenkins' and then 'Configure System'.

4.e. Add Git information.

4.f. Add Git user and email info under section "Git Plugin".

4.g. Click 'Save'.

Step 5: Configure a Jenkins Job.

5.a. From the Jenkins dashboard, navigate to 'New Job'.

5.b. Enter a 'Job Name' and select 'Build a maven2/3 project'. Click 'OK'.

5.c. Enter a 'Description'.

5.d. Select 'Discard Old Builds'.

5.e. Enter an amount by 'Max # of builds to keep'.

5.f. Select 'Git' and enter a 'Repository URL'. If you wanted to track a git repo on Github, this is where you would enter the git URL.

5.g. Check 'Poll SCM' and add '* * * * *' to 'Schedule'. '* * * * *' is a cron expression which means 'every minute'.

5.h. Under 'Build' add a Maven goal in 'Goals and options'.

5.i. Click 'Save'.

Step 6: Run the Job.

6.a. From the Jenkins dashboard, run the new job by clicking the clock with arrow icon on the far right. If everything is set up correctly, the job should run and a blue ball should appear. You may have to refresh the page after the job runs to refresh the ball.

If you need to debug a Jenkins job either while it is running or after it is finished, you can view console output. From the dashboard, click on the job name. Once on the job's page, hover over a link in the 'Build History' section and select 'Console Output'.

Also, when you push new commits to the git repo, Jenkins should recognize that and start the job automatically.

Piece of Cake!!!

Helpful Links

Install Jenkins on Windows as a Windows Service
Hello World - Maven, M2Eclipse and Eclipse
Setup Git on Windows

Wingsuit Flying

Wingsuit Flying on Wikipedia

Install Jenkins on Windows as a Windows Service

Installing Jenkins on Windows and setting up a Jenkins Windows Service, which starts Jenkins automatically whenever Windows is restarted is now easier than ever since there is a Jenkins Windows install wizard for it. This short tutorial shows how to setup Jenkins on Windows.

Step 1: Download the Windows native package from the Jenkins main website.

Step 2: Unpack the .zip file.

Step 3: Click through the install wizard.

Step 4: Verify that Jenkins is running. Open up a browser and go to: http://localhost:8080/. You should see the following:

Piece of Cake!