Tag Archives: java

Monitor your Jenkins build with an Arduino (and some Java code)

So I got my hands on an Arduino kit a while back but hadn’t played around with it much. Whilst I await for some books to arrive so I can learn basic electronics and circuits (am a developer without engineering/electronics background…) I thought it’d be fun to see if I could write something simple that could be useful in my day to day job as a Java developer.

One of the tools we use is Jenkins and whilst we get emails and check the Jenkins Dashboard to see if a build has failed,¬† developers often have a tendency to not check their emails or check Jenkins to see what the state of the build is… As a result it may be hours or even a few days before someone realises the build is not passing…

So it seemed fitting to write some code to get a LED light to blink if the build is failing. To do this you’ll need the following:

  • Jenkins with the build you want to monitor setup
  • Arduino (I’m using an Uno)
  • A LED (though for test purposes if you’re using an Uno pin 13 has a LED built in which should be sufficient)
  1. Wire up your LED to one of the pins or do what I did and use the built in LED on pin 13.
  2. Write some code in your language of choice to grab the build status from Jenkins and send it serially to the Arduino. I chose to grab the status as JSON, but there are other options available. I used Java and the Spring Framework to schedule a process to run every 5 seconds to grab the Jenkins status and send it across to the Arduino with the main grunt work being the code below: [sourcecode language=”java”]
    package com.delineneo.processor;

    import com.delineneo.communication.SerialCommunicator;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.scheduling.annotation.Scheduled;
    import org.springframework.stereotype.Component;
    import org.springframework.web.client.RestTemplate;

    import java.io.IOException;

    import static org.apache.commons.lang.StringUtils.contains;

    * Created by IntelliJ IDEA.
    * User: deline
    * Date: 2/03/12
    * Time: 8:33 PM
    public class JenkinsStatusProcessor {
    private static final String JENKINS_URL = "http://localhost:8080/job/JenkinsStatus/api/json" ;
    private static final String SUCCESS_BUILD_COLOR = "blue";
    public static final char BUILD_FAIL = ‘0’;
    public static final char BUILD_SUCCESS = ‘1’;

    private RestTemplate restTemplate;
    private SerialCommunicator serialCommunicator;

    public void process() {

    String jsonString = restTemplate.getForObject(JENKINS_URL, String.class);

    boolean buildSuccess = isBuildSuccessful(jsonString);
    try {
    serialCommunicator.send(buildSuccess ? BUILD_SUCCESS : BUILD_FAIL);
    } catch (IOException e) {

    private boolean isBuildSuccessful(String jsonString) {
    if (contains(jsonString, SUCCESS_BUILD_COLOR)) {
    return true;
    return false;

    public void setRestTemplate(RestTemplate restTemplate) {
    this.restTemplate = restTemplate;

    public void setSerialCommunicator(SerialCommunicator serialCommunicator) {
    this.serialCommunicator = serialCommunicator;

    In the process method we grab the status as JSON using Spring’s RestTemplate then search for the build status colours in the string. Blue represents success and I treat any other colour (yellow and red are the other ones) as a failure. We then send either a ‘0’ or ‘1’ for fail or success respectively.

    You might wonder why we send a char instead of a boolean… Serial write to the Arduino is as an int or byte array, and on the Arduino side read is done either as an int or a char. For example sending ‘A’ will be received via the Arduino as either the char ‘A’ or the int value 65 (the ascii value). This post on bildr gives you a bit more info on why one might choose to read values as and int instead of a char.

  3. Write some code for the Arduino to process the received data and set the LED to flashing if the build has failed. The code below listens on the serial port:
    [sourcecode language=”cpp”]
    /* JenkinsStatus will turn the LED at pin 13 on/off depending
    * on the value serially read.
    const int BUILD_SUCCESS = 49;
    int inByte;
    int currentPinValue = 0;

    void setup() {
    pinMode(13, OUTPUT);

    void loop() {
    if (Serial.available() > 0) {
    inByte = Serial.read();
    if (inByte == BUILD_SUCCESS) {
    digitalWrite(13, LOW);
    } else{
    digitalWrite(13, HIGH);
    } else {
    currentPinValue = digitalRead(13);
    if (currentPinValue == HIGH) {
    digitalWrite(13, LOW);
    digitalWrite(13, HIGH);

    In the loop if there’s data to be read we read it then determine if what state the LED on pin 13 needs to be in. The pin needs to be LOW (i.e. off) if the build is passing and HIGH (on) otherwise. Additionally, if there is no data to be read we want to keep the LED in a flashing state if it was set to HIGH (last read indicated build had failed).

So that’s pretty much the long short of it, the full code is available on my Git repo – https://github.com/deline/JenkinsStatus

Some thoughts on how JenkinsStatus could be improved:

  • Allow config of Jenkins details via properties files
  • Allow more than one Jenkins job to be monitored
  • Put in more LEDs for other states

Simple RegEx and Closure example in Groovy

I’ve been intermittently reading Groovy in Action for the last few nights and whilst it all seems pretty straight forward, for me the real grasping of an understanding comes by writing some code to affirm what was read. That posed the dilemma of what to write, as since leaving uni most of my learning experiences in Java (and development concepts in general) have been in relation to real world business style scenarios. I gave a thought back to my high school days where I learnt how to program. Why not just start with a somewhat simple/trivial problem – e.g. a factorial calculator, or sentence word reverser and go from there? Sure it’s not anything too swish, but it seems a good way to get an understanding of the language.

So here I present a simple solution in Groovy that uses RegEx and Closures to captalise the first letter of each word in a string. I’ll also show you an even neater solution after….

First up:


String testString = ‘the quick brown fox jumped over the lazy dog’
String regex = /bw*s?b/

testString.eachMatch(regex) { match ->
print match.capitalize()


Lines 1 and 2 should be pretty self explanatory. We’ve based our regex of the basis that a word consists of word characters only, may have a space after the last word character and has a word boundary on either side.

Lines 4-6 is where the cool stuff happens, as for each word match we make we want to upper case the first letter and print it out. The method eachMatch takes two arguments a String regex and a closure. From the Groovy docs‘A Groovy Closure is like a “code block” or a method pointer. It is a piece of code that is defined and then executed at a later point.’ In the example above we have defined the closure inline with one parameter match – parameters are listed before the ->. The closure calls capitalize on the match and prints it out.

We could have easily defined the closure separatley and provided it to eachMethod as such:

Closure capitalize = { match -> print match.capitalize() }
testString.eachMatch(regex, capitalize)

Seems pretty easy right? Not many lines of code and quite succinct about what is happening. Well as is often the case, I did a little Google and here’s an even easier solution:

String testString = ‘the quick brown fox jumped over the lazy dog’
print testString.split(‘ ‘).collect{ it.capitalize() }.join(‘ ‘)

In the end my solution was a first attempt into using Groovy to solve a problem without having much exposure to the language whilst at the same time trying not to use my Java mindset. After seeing the alternative solution on the Internet it kind of shows that if you know what to use Groovy can make things even simpler as it’s definitely cleaner without using the RegEx.

Installing Groovy on a Mac

Having heard about Groovy and Grails for the last few years but not having actually had a look at it I installed Groovy on my Mac the other week for a bit of a play. It’s always good and fun to have a look at a different language even if if you’re not going to use it in your day to day job. Coming from predominantly a Java background Groovy seemed like a good choice as it runs on the Java platform and the language is similar. Having had the opportunity to use Objective-C for a few months last year and seeing how in some ways it was more powerful than Java (but also in other ways frustrating), I was curious to see what power Groovy gave to a developer.

The first step though was to get Groovy installed on my Mac. So I thought I’d put a post up mainly for anyone new to developing on a Mac. Whilst I’ve had my Mac for a year or so, I hadn’t really had it setup for anything other than Java until recently, and there were definitely some things that were a little different to what I was used to on Windows as well from my prior limited stint in Ubuntu land.

These instructions are based on a setup for OS X. I’d imagine the setup may be similar on any other version?

  1. Java should already be installed on your machine. Confirm this by opening up a Terminal and typing in ‘java -version‘.
  2. Download the binary Zip release of Groovy from the Groovy site.
  3. Extract the contents into /usr/local – e.g. my install location is /usr/local/groovy-1.7.6/. You will probably need to need to use the sudo command for the extract as you will need to be superuser to write to the location.
  4. Check if a file called environment.plist exists in the following location /Users/YOUR_USER_NAME/.MacOSX. If it doesn’t create it.
  5. Open environment.plist in the Property List Editor
  6. Add an entry for JAVA_HOME if not present, ensure the value is the location of your Java installation. This should be /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home
  7. Add an entry for GROOVY_HOME if not present and ensure the value is the location Groovy is installed. E.g. /usr/local/groovy-1.7.6
  8. Add an entry for PATH if not present, and ensure the Groovy bin and Java bin directories are present by adding  $JAVA_HOME:$GROOVY_HOME/bin
  9. Log out and re log back in for the changes to take effect.
  10. Check that everything is all setup correctly by opening a Terminal and running groovy -version which should show you which version of Groovy is installed.

Easy integration with Spring Integration

So I’ve had the opportunity to use Spring Integration recently and I thought I’d do a blog post about it – partly for my own review/recap/learning but also for anyone out there looking to play around with it. In a nutshell Spring Integration lets you integrate with other systems without having to deal with all the boilerplate concerns of your typical enterprise integration solutions. It provides a number of integration adapters straight out of the box for common integration methods such as: files, jms, jdbc, ftp and so on (take a look at the Spring doco for the full set).

The general gist of things has you defining a series of channels of which the endpoint may be the entry or exit to the system. One endpoint may be the entry point to another channel. E.g. in the following A<——–>B is a channel with A as the input and B as the output endpoints. B<——–>C is another channel where the output B from the A<——–>B channel is the input and C the output.


To really see how it all hangs together I’ve knocked together a little working example to integrate with Twitter using the built in Twitter Adapter. The app basically polls Twitter with a search on a hashtag, adds a field to the header then passes the message on to a service to be dealt with – in this case we are just going to print out to System.out. Sounds complicating, but Spring makes it easy – take a look at src/main/resources/twitter-integration.xml.

<channel id="inboundMentionsChannel"/>
<channel id="inputServiceActivatorChannel"/>

This defines the channels, note that we haven’t actually specified what the endpoints are yet…


<twitter:search-inbound-channel-adapter query="#springintegration" channel="inboundMentionsChannel">
<poller fixed-rate="5000" max-messages-per-poll="3"/>

<header-enricher input-channel="inboundMentionsChannel" output-channel="inputServiceActivatorChannel">
<header name="headerField1" value="dummy header value"/>


This is the interesting stuff where we link all the endpoints and channels together. Lines 1-3 define the inbound adapter (endpoint) which connects the system with Twitter. This is a search-inbound-adapter that polls for a twitter search using the specified query – in this case the hashtag #springintegration.

Lines 4-7 defines a header enricher. This allows us to pop values into the message header that can be used downstream. For this example we’re just populating a field called ‘headerField1’ with a dummy value. We’re not actually going to use this field for anything in the example but I wanted to show how easy it was to add info to the message header. The header enricher also has an input channel and output channel specified. As you may have worked out the input to the header enricher is from the endpoint of the ‘inboundMentionsChannel’, which in this case will contain the results from the Twitter search. And the outbound channel is to a service activator which references the TwitterService bean (bean is autowired).

If you take a look at TwitterService.java you’ll see that it prints out to System.out and adds the tweet to a list. Running the test case TwitterIntegrationTest.java you can check that the output matches the expected tweet search result count of 3.