Initial commit

10 files changed, 786 insertions, 0 deletions

diff --git a/daemon/pom.xml b/daemon/pom.xml
new file mode 100644
index 0000000..f25d610
--- /dev/null
+++ b/daemon/pom.xml
@@ -0,0 +1,66 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>org.openslx.taskmanager</groupId>
+	<artifactId>taskmanager-daemon</artifactId>
+	<packaging>jar</packaging>
+	<version>1.0-SNAPSHOT</version>
+	<name>taskmanager-daemon</name>
+	<url>http://maven.apache.org</url>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+	</properties>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>3.1</version>
+				<configuration>
+					<source>1.7</source>
+					<target>1.7</target>
+				</configuration>
+			</plugin>
+			<plugin>
+				<artifactId>maven-assembly-plugin</artifactId>
+				<executions>
+					<execution>
+						<phase>package</phase>
+						<goals>
+							<goal>single</goal>
+						</goals>
+					</execution>
+				</executions>
+				<configuration>
+					<archive>
+						<manifest>
+							<mainClass>org.openslx.taskmanager.App</mainClass>
+						</manifest>
+					</archive>
+					<descriptorRefs>
+						<descriptorRef>jar-with-dependencies</descriptorRef>
+					</descriptorRefs>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>3.8.1</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.openslx.taskmanager</groupId>
+			<artifactId>taskmanager-api</artifactId>
+			<version>${project.version}</version>
+			<scope>compile</scope>
+		</dependency>
+	</dependencies>
+
+
+</project>
diff --git a/daemon/src/main/java/org/openslx/taskmanager/App.java b/daemon/src/main/java/org/openslx/taskmanager/App.java
new file mode 100644
index 0000000..c233229
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/App.java
@@ -0,0 +1,47 @@
+package org.openslx.taskmanager;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.SocketException;
+
+import junit.runner.ClassPathTestCollector;
+
+import org.apache.log4j.BasicConfigurator;
+import org.openslx.taskmanager.main.Taskmanager;
+import org.openslx.taskmanager.network.NetworkHandler;
+import org.openslx.taskmanager.util.ClassLoaderHack;
+
+/**
+ * Hello world!
+ * 
+ */
+public class App
+{
+
+	public static void main( String[] args ) throws SocketException
+	{
+		// Load all task plugins
+		File folder = new File( "./plugins" );
+		if ( !folder.exists() ) {
+			System.out.println( "No plugin folder found - nothing to do." );
+			System.exit( 1 );
+		}
+		for ( File file : folder.listFiles() ) {
+			if ( !file.isFile() || !file.toString().endsWith( ".jar" ) )
+				continue;
+			try {
+				ClassLoaderHack.addFile( file );
+			} catch ( IOException e ) {
+				e.printStackTrace();
+				System.out.println( "Could not add plugin: " + file.toString() );
+				System.exit( 1 );
+			}
+		}
+		BasicConfigurator.configure();
+		Environment.load( "config/environment" );
+		NetworkHandler.init();
+		Taskmanager.run();
+		// Wait for everything
+		NetworkHandler.join();
+	}
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/Environment.java b/daemon/src/main/java/org/openslx/taskmanager/Environment.java
new file mode 100644
index 0000000..acbfad4
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/Environment.java
@@ -0,0 +1,67 @@
+package org.openslx.taskmanager;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import org.apache.log4j.Logger;
+
+/**
+ * Holds the environment that tasks running a system command *should*
+ * use. The environment is read from a config file.
+ */
+public class Environment
+{
+
+	private static final Logger log = Logger.getLogger( Environment.class );
+
+	private static Map<String, String> env = new LinkedHashMap<>();
+
+	public static boolean load( String fileName )
+	{
+		try {
+			FileReader fileReader = new FileReader( fileName );
+			BufferedReader bufferedReader = new BufferedReader( fileReader );
+
+			Map<String, String> env = new LinkedHashMap<>();
+			String line = null;
+			while ( ( line = bufferedReader.readLine() ) != null ) {
+				if ( !line.matches( "^[a-zA-Z0-9_]+=" ) )
+					continue;
+				String[] part = line.split( "=", 2 );
+				env.put( part[0], part[1] );
+			}
+
+			bufferedReader.close();
+
+			Environment.env = env;
+			log.info( "Loaded " + env.size() + " environment lines." );
+		} catch ( IOException e ) {
+			log.info( "Could not load environment definition from " + fileName + ". Processes might use the same environment as this thread." );
+			return false;
+		}
+		return true;
+	}
+
+	public static void set( Map<String, String> environment )
+	{
+		environment.clear();
+		environment.putAll( env );
+	}
+
+	public static String[] get()
+	{
+		// Get reference to env so it doesn't change while in this function (load() from other thread)
+		Map<String, String> env = Environment.env;
+		String ret[] = new String[ env.size() ];
+		int i = 0;
+		for ( Entry<String, String> it : env.entrySet() ) {
+			ret[i++] = it.getKey() + "=" + it.getValue();
+		}
+		return ret;
+	}
+
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/Global.java b/daemon/src/main/java/org/openslx/taskmanager/Global.java
new file mode 100644
index 0000000..7ca2c2d
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/Global.java
@@ -0,0 +1,32 @@
+package org.openslx.taskmanager;
+
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+public class Global
+{
+
+	public static final int LISTEN_PORT = 9215;
+
+	public static final String TASK_PACKAGE_NAME = "org.openslx.taskmanager.tasks";
+
+	public static final long MAX_TASK_AGE = 24l * 3600l * 1000l;
+
+	public static final InetAddress LISTEN_ADDRESS;
+
+	public static volatile boolean doShutdown = false;
+
+	static
+	{
+		InetAddress la;
+		try {
+			la = Inet4Address.getByName( "127.0.0.1" );
+		} catch ( UnknownHostException e ) {
+			la = null;
+			e.printStackTrace();
+		}
+		LISTEN_ADDRESS = la;
+	}
+
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/main/Taskmanager.java b/daemon/src/main/java/org/openslx/taskmanager/main/Taskmanager.java
new file mode 100644
index 0000000..f3707ed
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/main/Taskmanager.java
@@ -0,0 +1,200 @@
+package org.openslx.taskmanager.main;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.apache.log4j.Logger;
+import org.openslx.taskmanager.Global;
+import org.openslx.taskmanager.api.AbstractTask;
+import org.openslx.taskmanager.api.TaskStatus;
+import org.openslx.taskmanager.util.ClassLoaderHack;
+import org.openslx.taskmanager.util.Util;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonSyntaxException;
+
+public class Taskmanager
+{
+
+	private static final Logger log = Logger.getLogger( Taskmanager.class );
+
+	private static final ExecutorService threadPool = Executors.newCachedThreadPool();
+
+	/**
+	 * Static gson object for (de)serialization
+	 */
+	private static final Gson gson = Util.explicitGsonInstance();
+
+	/**
+	 * Cache of known tasks
+	 */
+	private static final Map<String, Class<? extends AbstractTask>> tasks = new ConcurrentHashMap<>();
+
+	/**
+	 * All the running/finished task instances. The mainloop will call wait() on this and this object
+	 * is notified as soon as the mainloop should check if there is any task available that can be
+	 * run.
+	 */
+	private static final Map<String, AbstractTask> instances = new ConcurrentHashMap<>();
+
+	private static final Lock workLock = new ReentrantLock();
+	private static final Condition doCheckForWork = workLock.newCondition();
+
+	/*
+	 * Static methods
+	 */
+
+	/**
+	 * Return the status of the task with the given ID. If the task does not
+	 * exist, a pseudo-status instance is returned, with a status code of
+	 * NO_SUCH_TASK. This means it is guaranteed that this function never returns
+	 * null.
+	 * 
+	 * @param taskId - ID of the task to retrieve the status of
+	 * @return TaskStatus
+	 */
+	public static TaskStatus getTaskStatus( final String taskId )
+	{
+		AbstractTask task = instances.get( taskId );
+		if ( task == null )
+			return TaskStatus.ts_noSuchInstance;
+		return task.getStatus();
+	}
+
+	/**
+	 * Run the requested method as a new task. The json data may contain an explicit id for that
+	 * task, otherwise a random id is generated. If there's already a task running with the desired
+	 * id, an error is returned, and no new task will be created. The desired id has to be added to
+	 * the json data, as a field called "id".
+	 * 
+	 * @param task - The task name to be executed.
+	 * @param jsonData - JsonData to be passed to the task. All fields except "id" are ignored by the
+	 *           task manager.
+	 * @return the TaskStatus returned by the newly created task, or a NO_SUCH_TASK TaskStatus if
+	 *         there is no task registered under the given name.
+	 */
+	public static TaskStatus submitTask( final String task, final String jsonData )
+	{
+		// Get task class
+		Class<? extends AbstractTask> taskClass;
+		synchronized ( tasks ) {
+			taskClass = tasks.get( task );
+			if ( taskClass == null ) { // Not in map; either never called yet, or doesn't exist
+				taskClass = ClassLoaderHack.getClass( Global.TASK_PACKAGE_NAME, task, AbstractTask.class );
+				if ( taskClass == null ) { // Simply doesn't exist
+					log.warn( "Could not find " + task + " in " + Global.TASK_PACKAGE_NAME );
+					return TaskStatus.ts_noSuchTask;
+				}
+				tasks.put( task, taskClass ); // Cache for all future calls
+			}
+		}
+		// Instantiate using Gson
+		final AbstractTask taskInstance;
+		try {
+			taskInstance = gson.fromJson( jsonData, taskClass );
+		} catch ( JsonSyntaxException e ) {
+			log.warn( "Invocation request for " + task + " with invalid json: " + jsonData );
+			return TaskStatus.ts_jsonError;
+		}
+		if ( taskInstance == null ) {
+			log.warn( task + " exists, but could not be instanciated!" );
+			return TaskStatus.ts_noSuchConstructor;
+		}
+		if ( taskInstance.getId() == null ) {
+			log.warn( "Tried to launch " + task + " with null-id" );
+			return TaskStatus.ts_noSuchConstructor;
+		}
+		// Now check for id collision
+		synchronized ( instances ) {
+			if ( instances.containsKey( taskInstance.getId() ) ) {
+				log.info( "Ignoring task invocation of " + task + ": Duplicate ID: " + taskInstance.getId() );
+				return TaskStatus.ts_duplicateId;
+			}
+			instances.put( taskInstance.getId(), taskInstance );
+		}
+		AbstractTask parent = null;
+		if ( taskInstance.getParentTaskId() != null )
+			parent = instances.get( taskInstance.getParentTaskId() );
+		if ( taskInstance.init( parent ) ) {
+			checkForWork();
+		}
+		return taskInstance.getStatus();
+	}
+
+	public static void releaseTask( String taskId )
+	{
+		final AbstractTask task = instances.get( taskId );
+		if ( task != null )
+			task.release();
+	}
+
+	/**
+	 * Wakes up the Taskmanager's mainloop so it will check if any of the current task instances
+	 * is waiting for execution.
+	 */
+	protected static void checkForWork()
+	{
+		workLock.lock();
+		try {
+			doCheckForWork.signalAll();
+		} finally {
+			workLock.unlock();
+		}
+	}
+
+	public static void run()
+	{
+		try {
+			while ( !Global.doShutdown ) {
+				workLock.lock();
+				try {
+					doCheckForWork.await( 1, TimeUnit.MINUTES );
+				} finally {
+					workLock.unlock();
+				}
+				try {
+					for ( Iterator<AbstractTask> it = instances.values().iterator(); it.hasNext(); ) {
+						AbstractTask task = it.next();
+						if ( task.canBeReleased() ) {
+							it.remove();
+							log.debug( "Released task " + task.getClass().getSimpleName() + " (" + task.getId() + ")" );
+							continue;
+						}
+						if ( task.canStart() ) {
+							threadPool.execute( task );
+							log.debug( "Started Task " + task.getClass().getSimpleName() + " (" + task.getId() + ")" );
+						}
+					}
+				} catch ( RejectedExecutionException e ) {
+					log.warn( "ThreadPool rejected a task (" + e.getMessage() + ")" );
+				}
+			}
+		} catch ( InterruptedException e ) {
+			Thread.currentThread().interrupt();
+		} finally {
+			log.info( "Taskmanager mainloop finished." );
+			Global.doShutdown = true;
+			log.info( "Shutting down worker thread pool...." );
+			threadPool.shutdown();
+			try {
+				if ( threadPool.awaitTermination( 5, TimeUnit.MINUTES ) ) {
+					log.info( "Thread pool shut down!" );
+				} else {
+					log.info( "Trying to kill still running tasks...." );
+					threadPool.shutdownNow();
+				}
+			} catch ( InterruptedException e ) {
+				log.info( "Interrupted!" );
+			}
+		}
+	}
+
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/network/NetworkHandler.java b/daemon/src/main/java/org/openslx/taskmanager/network/NetworkHandler.java
new file mode 100644
index 0000000..3e2c8fd
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/network/NetworkHandler.java
@@ -0,0 +1,180 @@
+package org.openslx.taskmanager.network;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.SocketAddress;
+import java.net.SocketException;
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+import org.apache.log4j.Logger;
+import org.openslx.taskmanager.Global;
+
+/**
+ * The network listener that will receive incoming UDP packets, try to process
+ * them, and then send a reply.
+ */
+public class NetworkHandler implements Runnable
+{
+
+	private static final Logger log = Logger.getLogger( NetworkHandler.class );
+
+	// Static part
+
+	private static Thread recvThread = null;
+	private static Thread sendThread = null;
+	/**
+	 * Sender instance (Runnable handling outgoing packets)
+	 */
+	private static Sender sender = null;
+	/**
+	 * UDP socket for sending and receiving.
+	 */
+	private static DatagramSocket socket;
+
+	/**
+	 * Initialize the NetworkHandler by starting threads and opening the socket.
+	 */
+	public static void init() throws SocketException
+	{
+		if ( recvThread != null )
+			throw new RuntimeException( "Already initialized" );
+		socket = new DatagramSocket( Global.LISTEN_PORT, Global.LISTEN_ADDRESS );
+		recvThread = new Thread( new NetworkHandler() );
+		recvThread.start();
+		sendThread = new Thread( sender = new Sender() );
+		sendThread.start();
+	}
+
+	public static void shutdown()
+	{
+		socket.close();
+	}
+
+	public static void join()
+	{
+		try {
+			recvThread.join();
+			sendThread.join();
+		} catch ( InterruptedException e ) {
+			Thread.currentThread().interrupt();
+		}
+	}
+
+	// Class part
+
+	/**
+	 * Prepare and enqueue reply for client request.
+	 * Only ever to be called from the receiving thread. The reply message is crafted
+	 * and then handed over to the sending thread.
+	 * 
+	 * @param destination SocketAddress of the client
+	 * @param messageId The same ID the client used in it's request.
+	 *           It's echoed back to the client to enable request bursts, and has no meaning for the
+	 *           server.
+	 * @param status A TaskStatus instance to be serialized to json and sent to the client.
+	 */
+	private void send( SocketAddress destination, byte[] buffer )
+	{
+		final DatagramPacket packet;
+		try {
+			packet = new DatagramPacket( buffer, buffer.length, destination );
+		} catch ( SocketException e ) {
+			log.warn( "Could not construct datagram packet for target " + destination.toString() );
+			e.printStackTrace();
+			return;
+		}
+		sender.send( packet );
+	}
+
+	/**
+	 * Main loop of receiving thread - wait until a packet arrives, then try to handle/decode
+	 */
+	@Override
+	public void run()
+	{
+		byte readBuffer[] = new byte[ 66000 ];
+		try {
+			while ( !Global.doShutdown ) {
+				DatagramPacket packet = new DatagramPacket( readBuffer, readBuffer.length );
+				try {
+					socket.receive( packet );
+				} catch ( IOException e ) {
+					log.info( "IOException on UDP socket when reading: " + e.getMessage() );
+					Thread.sleep( 100 );
+					continue;
+				}
+				if ( packet.getLength() < 2 ) {
+					log.debug( "Message too short" );
+					continue;
+				}
+				String payload = new String( readBuffer, 0, packet.getLength(), StandardCharsets.UTF_8 );
+				try {
+					byte[] reply = RequestParser.handle( payload );
+					if ( reply != null )
+						send( packet.getSocketAddress(), reply );
+				} catch ( Throwable t ) {
+					log.error( "Exception in RequestParser: " + t.getMessage() );
+					t.printStackTrace();
+				}
+			}
+		} catch ( InterruptedException e ) {
+			Thread.currentThread().interrupt();
+		} finally {
+			Global.doShutdown = true;
+			log.info( "UDP receiver finished." );
+		}
+	}
+
+	/**
+	 * Private sending thread.
+	 * Use blocking queue, wait for packet to be added to it, then try to send.
+	 */
+	static class Sender implements Runnable
+	{
+
+		/**
+		 * Queue to stuff outgoing packets into.
+		 */
+		private final BlockingQueue<DatagramPacket> queue = new LinkedBlockingQueue<>( 128 );
+
+		/**
+		 * Wait until something is put into the queue, then send it.
+		 */
+		@Override
+		public void run()
+		{
+			try {
+				while ( !Global.doShutdown ) {
+					final DatagramPacket packet;
+					packet = queue.take();
+					try {
+						socket.send( packet );
+					} catch ( IOException e ) {
+						log.debug( "Could not send UDP packet to " + packet.getAddress().getHostAddress().toString() );
+					}
+				}
+			} catch ( InterruptedException e ) {
+				Thread.currentThread().interrupt();
+			} finally {
+				Global.doShutdown = true;
+				log.info( "UDP sender finished." );
+			}
+		}
+
+		/**
+		 * Add something to the outgoing packet queue.
+		 * Called from the receiving thread.
+		 */
+		public void send( DatagramPacket packet )
+		{
+			if ( queue.offer( packet ) )
+				return;
+			log.warn( "Could not add packet to queue: Full" );
+		}
+
+	}
+
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/network/RequestParser.java b/daemon/src/main/java/org/openslx/taskmanager/network/RequestParser.java
new file mode 100644
index 0000000..d2cfb21
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/network/RequestParser.java
@@ -0,0 +1,66 @@
+package org.openslx.taskmanager.network;
+
+import java.nio.charset.StandardCharsets;
+
+import org.apache.log4j.Logger;
+import org.openslx.taskmanager.api.TaskStatus;
+import org.openslx.taskmanager.main.Taskmanager;
+
+import com.google.gson.Gson;
+
+public class RequestParser
+{
+	private static final Logger log = Logger.getLogger( RequestParser.class );
+
+	/**
+	 * Our very own gson instance (for serializing replies)
+	 */
+	private static final Gson sendGson = new Gson();
+
+	/**
+	 * Handle the given unparsed request.
+	 * 
+	 * @param source source of the request, where the reply will be send to (if any)
+	 * @param payload Packet data received from network, already converted to a string
+	 */
+	public static byte[] handle( String payload )
+	{
+		String[] parts = payload.split( " *, *", 3 );
+		// Message format is "<message id>, <command>, <command payload/argument>"
+		if ( parts.length != 3 ) {
+			log.debug( "Could not split message" );
+			return null;
+		}
+		// Look at parts[1], if it's "status" it's a request for the task
+		// with the ID given in parts[2]
+		if ( parts[1].equals( "status" ) ) {
+			TaskStatus status = Taskmanager.getTaskStatus( parts[2] );
+			return serialize( parts[0], status );
+		}
+		// Now check if parts[1] is "release"
+		if ( parts[1].equals( "release" ) ) {
+			Taskmanager.releaseTask( parts[2] );
+			return null;
+		}
+		// Anything else in parts[0] will be treated as a fresh task invocation, so let's
+		// pass it on to the task manager.
+		TaskStatus status = Taskmanager.submitTask( parts[1], parts[2] );
+		return serialize( parts[0], status );
+	}
+
+	private static byte[] serialize( String messageId, TaskStatus status )
+	{
+		String data;
+		try {
+			synchronized ( sendGson ) {
+				data = sendGson.toJson( status );
+			}
+		} catch ( Throwable e ) {
+			log.warn( "Could not serialize reply with TaskStatus " + status.getStatusObjectClassName() );
+			log.warn( e.toString() );
+			return null;
+		}
+		return ( messageId + ',' + data ).getBytes( StandardCharsets.UTF_8 );
+	}
+
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/util/ClassLoaderHack.java b/daemon/src/main/java/org/openslx/taskmanager/util/ClassLoaderHack.java
new file mode 100644
index 0000000..1a02ff7
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/util/ClassLoaderHack.java
@@ -0,0 +1,66 @@
+package org.openslx.taskmanager.util;
+
+import java.io.File;
+import java.io.IOException;
+import java.lang.reflect.Method;
+import java.net.URL;
+import java.net.URLClassLoader;
+
+public class ClassLoaderHack
+{
+	@SuppressWarnings( "rawtypes" )
+	private static final Class[] parameters = new Class[] { URL.class };
+
+	public static void addFile( String s ) throws IOException
+	{
+		File f = new File( s );
+		addFile( f );
+	}
+
+	public static void addFile( File f ) throws IOException
+	{
+		addURL( f.toURI().toURL() );
+	}
+
+	public static void addURL( URL u ) throws IOException
+	{
+		URLClassLoader sysloader = (URLClassLoader)ClassLoader.getSystemClassLoader();
+		Class<URLClassLoader> sysclass = URLClassLoader.class;
+
+		try {
+			Method method = sysclass.getDeclaredMethod( "addURL", parameters );
+			method.setAccessible( true );
+			method.invoke( sysloader, new Object[] { u } );
+			System.out.println( "Loaded " + u.toString() );
+		} catch ( Throwable t ) {
+			t.printStackTrace();
+			throw new IOException( "Error, could not add URL to system classloader" );
+		}
+
+	}
+
+	/**
+	 * Get Class meta-object for given class in package. Only return class if it's somehow
+	 * extending from given baseClass.
+	 * 
+	 * @param packageName package to search in
+	 * @param className name of class to look for
+	 * @param baseClass class the class in question has to be extended from
+	 * @return class meta object, or null if not found
+	 */
+	@SuppressWarnings( "unchecked" )
+	public static <T> Class<? extends T> getClass( String packageName, String className, Class<T> baseClass )
+	{
+		final Class<?> clazz;
+		try {
+			clazz = Class.forName( packageName + '.' + className, true, ClassLoader.getSystemClassLoader() );
+		} catch ( ClassNotFoundException e ) {
+			return null;
+		}
+		if ( clazz == null || ( baseClass != null && !baseClass.isAssignableFrom( clazz ) ) ) {
+			return null;
+		}
+		return (Class<? extends T>)clazz;
+	}
+
+}
diff --git a/daemon/src/main/java/org/openslx/taskmanager/util/Util.java b/daemon/src/main/java/org/openslx/taskmanager/util/Util.java
new file mode 100644
index 0000000..bf52ecb
--- /dev/null
+++ b/daemon/src/main/java/org/openslx/taskmanager/util/Util.java
@@ -0,0 +1,24 @@
+package org.openslx.taskmanager.util;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+public class Util
+{
+
+	private static GsonBuilder gsonBuilder = new GsonBuilder();
+
+	/**
+	 * Small helper to create a gson instance that will only handle class members with the
+	 * "@Exposed" annotation. Decided against the default of explicitly excluding fields by
+	 * making them transient, as you might easily forget to exclude an important field, which
+	 * can in turn be a security issue.
+	 * 
+	 * @return Gson instance
+	 */
+	public static Gson explicitGsonInstance()
+	{
+		return gsonBuilder.excludeFieldsWithoutExposeAnnotation().create();
+	}
+
+}
diff --git a/daemon/src/test/java/org/openslx/taskmanager/AppTest.java b/daemon/src/test/java/org/openslx/taskmanager/AppTest.java
new file mode 100644
index 0000000..feac8e7
--- /dev/null
+++ b/daemon/src/test/java/org/openslx/taskmanager/AppTest.java
@@ -0,0 +1,38 @@
+package org.openslx.taskmanager;
+
+import junit.framework.Test;
+import junit.framework.TestCase;
+import junit.framework.TestSuite;
+
+/**
+ * Unit test for simple App.
+ */
+public class AppTest 
+    extends TestCase
+{
+    /**
+     * Create the test case
+     *
+     * @param testName name of the test case
+     */
+    public AppTest( String testName )
+    {
+        super( testName );
+    }
+
+    /**
+     * @return the suite of tests being tested
+     */
+    public static Test suite()
+    {
+        return new TestSuite( AppTest.class );
+    }
+
+    /**
+     * Rigourous Test :-)
+     */
+    public void testApp()
+    {
+        assertTrue( true );
+    }
+}