Embedding Jenkins in Java App

The Continuous Integration server Jenkins can easily be deployed to any Servlet container or run in standalone mode (see Starting Jenkins).

However, sometimes it can be handy to be able to start Jenkins from within another Java application. I like this option since this 'manager' Java app can easily be deployed to other systems and platforms (without having to install Tomcat/Jetty etc). It is also useful to easily start Jenkins from an eclipse workspace (just run the Java file :) ).

The only way I found to achieve this is to use Java to start anther OS process and then control Jenkins through this process.

Please find below example code to start a Jenkins process from a Java application. Don't forget to change the paths and ports given as static variables in the beginning to your environment!

public class StartJenkins {

/**
 * Location of Jenkins executable
 */
 public static String JENKINS_WAR = "M:\\apps\\jenkins\\jenkins.war";

/**
 * Locations of Settings and Jobs
 */
 public static String JENKINS_HOME = "M:\\apps\\jenkins\\.jenkins";

/**
 * The Http port on which Jenkins web server shall be started.
 */
 public static String HTTP_PORT = "9090";

/**
 * The Https port on which Jenkins web server shall be started.
 */
 public static String HTTPS_PORT = "9999";

/**
 * AJP13 port for Jenkins.
 */
 public static String AJP13_PORT = "9003";

/**
 * @param args
 * @throws IOException
 */
 public static void main(final String[] args) throws IOException {
 final Process jenkins = startJenkinsProcess();

System.out.println("Press 'q' + enter to kill Jenkins");
 while (System.in.read() != Character.valueOf('q')) {
 System.out.println("Press 'q' + enter to kill Jenkins");
 }
 jenkins.destroy();
 System.out.println("Jenkins is done for!");
 }

public static Process startJenkinsProcess() {
 try {

final Runtime rt = Runtime.getRuntime();
 final Process proc = rt.exec("java -DJENKINS_HOME=" + JENKINS_HOME
 + " -jar " + JENKINS_WAR + " --httpPort=" + HTTP_PORT
 + " --httpsPort=" + HTTPS_PORT + " --ajp13Port="
 + AJP13_PORT);

final StreamRedirectorThread errorStreamProcessor = new StreamRedirectorThread(
 proc.getErrorStream(), "err", System.err);

final StreamRedirectorThread outputStreamProcessor = new StreamRedirectorThread(
 proc.getInputStream(), "out", System.out);

// start processors for output and error stream
 errorStreamProcessor.start();
 outputStreamProcessor.start();

return proc;

} catch (final Throwable t) {
 throw new RuntimeException(t);
 }

}

/**
 * based on <a
 * href="http://www.javaworld.com/jw-12-2000/jw-1229-traps.html?page=4">When
 * Runtime.exec() won't</a>
 *
 *
 */
 public static class StreamRedirectorThread extends Thread {
 InputStream is;
 String type;
 OutputStream redirect;

StreamRedirectorThread(final InputStream is, final String type,
 final OutputStream redirect) {
 this.is = is;
 this.type = type;
 this.redirect = redirect;
 }

@Override
 public void run() {
 try {
 PrintWriter redirectedWriter = null;

redirectedWriter = new PrintWriter(redirect);

final InputStreamReader isr = new InputStreamReader(is);
 final BufferedReader br = new BufferedReader(isr);
 String line = null;
 while ((line = br.readLine()) != null) {
 redirectedWriter.println(line);
 }

redirectedWriter.flush();

} catch (final IOException ioe) {
 ioe.printStackTrace();
 }
 }
 }

}