Add template for assignment 2

ass2-aop/pom.xml

@@ -0,0 +1,45 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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/xsd/maven-4.0.0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>at.ac.tuwien.infosys.dst</groupId>
+    <artifactId>dst</artifactId>
+    <version>2021.1</version>
+    <relativePath>..</relativePath>
+  </parent>
+
+  <artifactId>ass2-aop</artifactId>
+
+  <packaging>jar</packaging>
+
+  <name>DST :: Assignment 2 :: Aspect-oriented Programming</name>
+
+
+  <dependencies>
+    <dependency>
+      <groupId>commons-io</groupId>
+      <artifactId>commons-io</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.aspectj</groupId>
+      <artifactId>aspectjrt</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.aspectj</groupId>
+      <artifactId>aspectjweaver</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-aop</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.commons</groupId>
+      <artifactId>commons-lang3</artifactId>
+    </dependency>
+  </dependencies>
+
+</project>

ass2-aop/src/main/java/dst/ass2/aop/IPluginExecutable.java

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+package dst.ass2.aop;
+
+/**
+ * Implementations of this interface are executable by the IPluginExecutor.
+ */
+public interface IPluginExecutable {
+
+    /**
+     * Called when this plugin is executed.
+     */
+    void execute();
+
+    /**
+     * Called when the execution of the plugin is interrupted
+     */
+    void interrupted();
+}

ass2-aop/src/main/java/dst/ass2/aop/IPluginExecutor.java

@@ -0,0 +1,40 @@
+package dst.ass2.aop;
+
+import java.io.File;
+
+/**
+ * The plugin executor interface.
+ */
+public interface IPluginExecutor {
+
+    /**
+     * Adds a directory to monitor.
+     * May be called before and also after start has been called.
+     *
+     * @param dir the directory to monitor.
+     */
+    void monitor(File dir);
+
+    /**
+     * Stops monitoring the specified directory.
+     * May be called before and also after start has been called.
+     *
+     * @param dir the directory which should not be monitored anymore.
+     */
+    void stopMonitoring(File dir);
+
+    /**
+     * Starts the plugin executor.
+     * All added directories will be monitored and any .jar file processed.
+     * If there are any {@link IPluginExecutable} implementations,
+     * they are executed within own threads.
+     */
+    void start();
+
+    /**
+     * Stops the plugin executor.
+     * The monitoring of directories and the execution
+     * of the plugins should stop as soon as possible.
+     */
+    void stop();
+}

ass2-aop/src/main/java/dst/ass2/aop/PluginExecutorFactory.java

@@ -0,0 +1,10 @@
+package dst.ass2.aop;
+
+public class PluginExecutorFactory {
+
+    public static IPluginExecutor createPluginExecutor() {
+        // TODO
+        return null;
+    }
+
+}

ass2-aop/src/main/java/dst/ass2/aop/logging/Invisible.java

@@ -0,0 +1,11 @@
+package dst.ass2.aop.logging;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface Invisible {
+}

ass2-aop/src/main/java/dst/ass2/aop/logging/LoggingAspect.java

@@ -0,0 +1,7 @@
+package dst.ass2.aop.logging;
+
+public class LoggingAspect {
+
+    // TODO
+
+}

ass2-aop/src/main/java/dst/ass2/aop/management/ManagementAspect.java

@@ -0,0 +1,7 @@
+package dst.ass2.aop.management;
+
+public class ManagementAspect {
+
+    // TODO
+
+}

ass2-aop/src/main/java/dst/ass2/aop/management/Timeout.java

@@ -0,0 +1,12 @@
+package dst.ass2.aop.management;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface Timeout {
+    long value();
+}

ass2-aop/src/test/java/dst/ass2/aop/event/Event.java

@@ -0,0 +1,74 @@
+package dst.ass2.aop.event;
+
+import org.springframework.util.Assert;
+
+import dst.ass2.aop.IPluginExecutable;
+
+/**
+ * Events triggered by {@link IPluginExecutable}s.
+ */
+public class Event {
+    private final long time = System.currentTimeMillis();
+    private Class<? extends IPluginExecutable> pluginClass;
+    private EventType type;
+    private String message;
+
+    public Event(EventType type, Class<? extends IPluginExecutable> pluginClass, String message) {
+        this.type = type;
+        this.pluginClass = pluginClass;
+        this.message = message;
+
+        StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
+        int pos = stackTrace[1].getMethodName().equals("<init>") ? 1 : 2;
+        Assert.state(stackTrace[pos].getMethodName().equals("<init>"), "Invalid Event Creation");
+        Assert.state(stackTrace[pos + 1].getClassName().equals(EventBus.class.getName()), "Invalid Event Creation");
+        Assert.state(stackTrace[pos + 1].getMethodName().equals("add"), "Invalid Event Creation");
+    }
+
+    /**
+     * Returns the time when the event occurred.
+     *
+     * @return the event creation time
+     */
+    public long getTime() {
+        return time;
+    }
+
+    /**
+     * Returns the type of the plugin that triggered the event.
+     *
+     * @return the plugin type
+     */
+    public Class<? extends IPluginExecutable> getPluginClass() {
+        return pluginClass;
+    }
+
+    /**
+     * Returns the type of the event.
+     *
+     * @return the event type
+     */
+    public EventType getType() {
+        return type;
+    }
+
+    /**
+     * Returns the message of the event
+     *
+     * @return the event message
+     */
+    public String getMessage() {
+        return message;
+    }
+
+    @Override
+    public String toString() {
+        final StringBuilder sb = new StringBuilder();
+        sb.append("Event");
+        sb.append("{time=").append(time);
+        sb.append(", pluginClass=").append(pluginClass);
+        sb.append(", type=").append(type);
+        sb.append('}');
+        return sb.toString();
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/event/EventBus.java

@@ -0,0 +1,135 @@
+package dst.ass2.aop.event;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.aop.support.AopUtils;
+
+import dst.ass2.aop.IPluginExecutable;
+
+/**
+ * Stateful event bus that stores events triggered by executable plugins.
+ * <p/>
+ * Note that this implementation is thread safe.
+ */
+public class EventBus {
+    private static final EventBus instance = new EventBus();
+    private final List<Event> events = new ArrayList<Event>();
+
+    public static EventBus getInstance() {
+        return instance;
+    }
+
+    private EventBus() {
+    }
+
+    /**
+     * Returns all events of the certain type(s).<br/>
+     * If no types are specified, all events are returned instead.
+     *
+     * @param types the event types
+     * @return list of all events of the given types.
+     */
+    public List<Event> getEvents(EventType... types) {
+        synchronized (events) {
+            if (types == null || types.length == 0) {
+                return new ArrayList<Event>(events);
+            } else {
+                List<Event> list = new ArrayList<Event>();
+                for (Event event : events) {
+                    for (EventType type : types) {
+                        if (type == event.getType()) {
+                            list.add(event);
+                        }
+                    }
+                }
+                return list;
+            }
+        }
+    }
+
+    /**
+     * Resets the event bus by purging the event history.
+     */
+    public synchronized void reset() {
+        synchronized (events) {
+            events.clear();
+        }
+    }
+
+    /**
+     * Adds a new event of a certain type triggered by the given plugin.
+     *
+     * @param type the event type
+     * @param pluginExecutable the plugin that triggered the event
+     * @param message the event message
+     */
+    @SuppressWarnings("unchecked")
+    public void add(EventType type, IPluginExecutable pluginExecutable, String message) {
+        add(type, (Class<? extends IPluginExecutable>) AopUtils.getTargetClass(pluginExecutable), message);
+    }
+
+    /**
+     * Adds a new event of a certain type triggered by a plugin of the given type.
+     *
+     * @param type the event type
+     * @param pluginType the type of the plugin
+     * @param message the event message
+     */
+    public void add(EventType type, Class<? extends IPluginExecutable> pluginType, String message) {
+        Event event = new Event(type, pluginType, message);
+        synchronized (events) {
+            events.add(event);
+        }
+    }
+
+    /**
+     * Returns the number of events of a certain type fired by this event bus.
+     *
+     * @param type the event type
+     * @return number of events
+     */
+    public int count(EventType type) {
+        int counter = 0;
+        synchronized (events) {
+            for (Event event : events) {
+                if (event.getType() == type) {
+                    counter++;
+                }
+            }
+        }
+        return counter;
+    }
+
+    /**
+     * Returns the number of events fired so far.
+     *
+     * @return number of events
+     */
+    public int size() {
+        return events.size();
+    }
+
+    /**
+     * Checks if there was at least one event of a certain type triggered by a plugin with the given full-qualified
+     * class name.
+     *
+     * If {@code pluginType} is {@code null}, the type of the plugin is not checked. The same is true for {@code type}.
+     * If all parameters are {@code null}, {@code true} is returned if there is at least one event.
+     *
+     * @param pluginType the class name of the plugin
+     * @param type the type of the event
+     * @return {@code true} if there is at least one event matching the criteria, {@code false} otherwise
+     */
+    public boolean has(String pluginType, EventType type) {
+        synchronized (events) {
+            for (Event event : events) {
+                if ((pluginType == null || pluginType.equals(event.getPluginClass().getName()))
+                        && (type == null || type == event.getType())) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/event/EventBusHandler.java

@@ -0,0 +1,38 @@
+package dst.ass2.aop.event;
+
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+
+import dst.ass2.aop.IPluginExecutable;
+
+/**
+ * Logging handler that uses the {@link EventBus} for publishing events.
+ */
+public class EventBusHandler extends Handler {
+    @SuppressWarnings("unchecked")
+    @Override
+    public void publish(LogRecord record) {
+        if (record.getLoggerName().endsWith("PluginExecutable") && record.getMessage().contains("PluginExecutable")) {
+            try {
+                Class<? extends IPluginExecutable> clazz = (Class<? extends IPluginExecutable>) Class.forName(record.getLoggerName());
+                EventBus.getInstance().add(EventType.INFO, clazz, record.getSourceClassName());
+            } catch (ClassNotFoundException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    /**
+     * Simply does nothing.
+     */
+    @Override
+    public void flush() {
+    }
+
+    /**
+     * Simply does nothing.
+     */
+    @Override
+    public void close() {
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/event/EventType.java

@@ -0,0 +1,5 @@
+package dst.ass2.aop.event;
+
+public enum EventType {
+    PLUGIN_START, PLUGIN_END, INFO
+}

ass2-aop/src/test/java/dst/ass2/aop/sample/AbstractPluginExecutable.java

@@ -0,0 +1,28 @@
+package dst.ass2.aop.sample;
+
+import org.springframework.aop.support.AopUtils;
+
+import dst.ass2.aop.IPluginExecutable;
+import dst.ass2.aop.event.EventBus;
+import dst.ass2.aop.event.EventType;
+
+public abstract class AbstractPluginExecutable implements IPluginExecutable {
+    @Override
+    public void execute() {
+        EventBus eventBus = EventBus.getInstance();
+        eventBus.add(EventType.PLUGIN_START, this, AopUtils.getTargetClass(this).getSimpleName() + " is executed!");
+
+        try {
+            Thread.sleep(1000);
+        } catch (InterruptedException e) {
+            // Should not happen but is not critical so the stack trace is printed to grab some attention ;-)
+            e.printStackTrace();
+        }
+
+        eventBus.add(EventType.PLUGIN_END, this, AopUtils.getTargetClass(this).getSimpleName() + " is finished!");
+    }
+
+    @Override
+    public void interrupted() {
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/sample/InterruptedPluginExecutable.java

@@ -0,0 +1,37 @@
+package dst.ass2.aop.sample;
+
+import org.springframework.aop.support.AopUtils;
+
+import dst.ass2.aop.IPluginExecutable;
+import dst.ass2.aop.event.EventBus;
+import dst.ass2.aop.event.EventType;
+import dst.ass2.aop.logging.Invisible;
+import dst.ass2.aop.management.Timeout;
+
+public class InterruptedPluginExecutable implements IPluginExecutable {
+    private boolean interrupted = false;
+
+    @Override
+    @Invisible
+    @Timeout(2000)
+    public void execute() {
+        EventBus eventBus = EventBus.getInstance();
+        eventBus.add(EventType.PLUGIN_START, this, AopUtils.getTargetClass(this).getSimpleName() + " is executed!");
+
+        while (!interrupted) {
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                // Should not happen but is not critical so the stack trace is printed to grab some attention ;-)
+                e.printStackTrace();
+            }
+        }
+
+        eventBus.add(EventType.PLUGIN_END, this, AopUtils.getTargetClass(this).getSimpleName() + " is finished!");
+    }
+
+    @Override
+    public void interrupted() {
+        interrupted = true;
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/sample/InvisiblePluginExecutable.java

@@ -0,0 +1,11 @@
+package dst.ass2.aop.sample;
+
+import dst.ass2.aop.logging.Invisible;
+
+public class InvisiblePluginExecutable extends AbstractPluginExecutable {
+    @Override
+    @Invisible
+    public void execute() {
+        super.execute();
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/sample/LoggingPluginExecutable.java

@@ -0,0 +1,9 @@
+package dst.ass2.aop.sample;
+
+import java.util.logging.Logger;
+
+public class LoggingPluginExecutable extends AbstractPluginExecutable {
+    @SuppressWarnings("unused")
+    private static Logger log = Logger.getLogger(LoggingPluginExecutable.class
+            .getName());
+}

ass2-aop/src/test/java/dst/ass2/aop/sample/SystemOutPluginExecutable.java

@@ -0,0 +1,4 @@
+package dst.ass2.aop.sample;
+
+public class SystemOutPluginExecutable extends AbstractPluginExecutable {
+}

ass2-aop/src/test/java/dst/ass2/aop/tests/Ass2_4_1Test.java

@@ -0,0 +1,151 @@
+package dst.ass2.aop.tests;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.List;
+
+import dst.ass2.aop.IPluginExecutor;
+import dst.ass2.aop.PluginExecutorFactory;
+import dst.ass2.aop.event.Event;
+import dst.ass2.aop.event.EventBus;
+import dst.ass2.aop.event.EventType;
+import dst.ass2.aop.util.PluginUtils;
+import org.apache.commons.io.FileUtils;
+import org.junit.*;
+
+public class Ass2_4_1Test {
+    static final String SIMPLE_PLUGIN = "dst.ass2.aop.sample.SimplePluginExecutable";
+    IPluginExecutor executor;
+    EventBus eventBus = EventBus.getInstance();
+
+    @BeforeClass
+    public static void beforeClass() {
+        Assert.assertEquals("Cannot create temporary plugin directory: " + PluginUtils.PLUGINS_DIR.getAbsolutePath(),
+                true, PluginUtils.PLUGINS_DIR.isDirectory() || PluginUtils.PLUGINS_DIR.mkdirs());
+    }
+
+    @AfterClass
+    public static void afterClass() throws IOException {
+        FileUtils.forceDeleteOnExit(PluginUtils.PLUGINS_DIR);
+    }
+
+    @Before
+    public void before() {
+        PluginUtils.cleanPluginDirectory();
+        executor = PluginExecutorFactory.createPluginExecutor();
+        executor.monitor(PluginUtils.PLUGINS_DIR);
+        executor.start();
+        eventBus.reset();
+    }
+
+    @After
+    public void after() {
+        executor.stop();
+        eventBus.reset();
+        PluginUtils.cleanPluginDirectory();
+    }
+
+    /**
+     * Executing plugin copied to plugin directory.
+     */
+    @Test(timeout = PluginUtils.PLUGIN_TEST_TIMEOUT)
+    public void copiedPlugin_isExecutedCorrectly() throws Exception {
+        // Preparing new plugin
+        PluginUtils.preparePlugin(PluginUtils.SIMPLE_FILE);
+
+        // Periodically check for the plugin to be executed
+        while (eventBus.size() != 2) {
+            Thread.sleep(100);
+        }
+
+        // Verify that the plugin was started and stopped orderly
+        assertTrue(SIMPLE_PLUGIN + " was not started properly.", eventBus.has(SIMPLE_PLUGIN, EventType.PLUGIN_START));
+        assertTrue(SIMPLE_PLUGIN + " did not finish properly.", eventBus.has(SIMPLE_PLUGIN, EventType.PLUGIN_END));
+    }
+
+    /**
+     * Checking that each plugin JAR uses its own ClassLoader.
+     */
+    @Test(timeout = PluginUtils.PLUGIN_TEST_TIMEOUT)
+    public void samePlugins_useSeparateClassLoaders() throws Exception {
+        // Preparing two plugins
+        PluginUtils.preparePlugin(PluginUtils.SIMPLE_FILE);
+        PluginUtils.preparePlugin(PluginUtils.SIMPLE_FILE);
+
+        // Periodically check for the plugins to be executed
+        while (eventBus.size() != 4) {
+            Thread.sleep(100);
+        }
+
+		/*
+         * Verify that the plugins were loaded by different classloaders.
+		 * This can be checked by comparing the ClassLoaders or comparing the classes themselves.
+		 * In other words, if a class is loaded by two different ClassLoaders, it holds that
+		 * a.getClass() != b.getClass() even if the byte code is identical.
+		 */
+        List<Event> events = eventBus.getEvents(EventType.PLUGIN_START);
+        String msg = "Both plugins where loaded by the same ClassLoader";
+        assertNotSame(msg, events.get(0).getPluginClass().getClassLoader(), events.get(1).getPluginClass().getClassLoader());
+        assertNotSame(msg, events.get(0).getPluginClass(), events.get(1).getPluginClass());
+    }
+
+    /**
+     * Checking whether two plugins in a single JAR are executed concurrently.
+     */
+    @Test(timeout = PluginUtils.PLUGIN_TEST_TIMEOUT)
+    public void allPlugins_executeConcurrently() throws Exception {
+        // Start a plugin containing two IPluginExecutable classes
+        PluginUtils.preparePlugin(PluginUtils.ALL_FILE);
+
+        // Periodically check for the plugins to be executed
+        while (eventBus.size() != 4) {
+            Thread.sleep(100);
+        }
+
+        // Check that there is exactly one start and end event each
+        List<Event> starts = eventBus.getEvents(EventType.PLUGIN_START);
+        List<Event> ends = eventBus.getEvents(EventType.PLUGIN_END);
+        assertEquals("EventBus must contain exactly 2 start events.", 2, starts.size());
+        assertEquals("EventBus must contain exactly 2 end events.", 2, ends.size());
+
+        // Verify that the plugins were started concurrently
+        String msg = "All plugins should have been started before the first ended - %d was after %d.";
+        for (Event end : ends) {
+            for (Event start : starts) {
+                assertTrue(String.format(msg, start.getTime(), end.getTime()), start.getTime() < end.getTime());
+            }
+        }
+    }
+
+    /**
+     * Checking whether two plugin JARs are executed concurrently.
+     */
+    @Test(timeout = PluginUtils.PLUGIN_TEST_TIMEOUT)
+    public void multiplePlugins_executeConcurrently() throws Exception {
+        // Start two plugins at once
+        PluginUtils.preparePlugin(PluginUtils.SIMPLE_FILE);
+        PluginUtils.preparePlugin(PluginUtils.SIMPLE_FILE);
+
+        // Periodically check for the plugins to be executed
+        while (eventBus.size() != 4) {
+            Thread.sleep(100);
+        }
+
+        // Check that there is exactly one start and end event each
+        List<Event> starts = eventBus.getEvents(EventType.PLUGIN_START);
+        List<Event> ends = eventBus.getEvents(EventType.PLUGIN_END);
+        assertEquals("EventBus must contain exactly 2 start events.", 2, starts.size());
+        assertEquals("EventBus must contain exactly 2 end events.", 2, ends.size());
+
+        // Verify that the plugins were started concurrently.
+        String msg = "All plugins should have been started before the first ended - %d was after %d.";
+        for (Event end : ends) {
+            for (Event start : starts) {
+                assertTrue(String.format(msg, start.getTime(), end.getTime()), start.getTime() < end.getTime());
+            }
+        }
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/tests/Ass2_4_2Test.java

@@ -0,0 +1,180 @@
+package dst.ass2.aop.tests;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.lang.reflect.Method;
+import java.util.List;
+import java.util.Map;
+
+import dst.ass2.aop.IPluginExecutable;
+import dst.ass2.aop.event.Event;
+import dst.ass2.aop.event.EventBus;
+import dst.ass2.aop.event.EventType;
+import dst.ass2.aop.sample.InvisiblePluginExecutable;
+import dst.ass2.aop.sample.LoggingPluginExecutable;
+import dst.ass2.aop.sample.SystemOutPluginExecutable;
+import dst.ass2.aop.util.PluginUtils;
+import org.aspectj.lang.annotation.After;
+import org.aspectj.lang.annotation.Around;
+import org.aspectj.lang.annotation.Aspect;
+import org.aspectj.lang.annotation.Before;
+import org.aspectj.weaver.internal.tools.PointcutExpressionImpl;
+import org.aspectj.weaver.tools.ShadowMatch;
+import org.junit.Test;
+import org.springframework.aop.PointcutAdvisor;
+import org.springframework.aop.framework.Advised;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.util.ReflectionUtils;
+
+import dst.ass2.aop.logging.Invisible;
+import dst.ass2.aop.logging.LoggingAspect;
+
+public class Ass2_4_2Test {
+    final EventBus eventBus = EventBus.getInstance();
+
+    @org.junit.Before
+    @org.junit.After
+    public void beforeAndAfter() {
+        eventBus.reset();
+    }
+
+    /**
+     * Verifies that the {@link LoggingAspect} is a valid AspectJ aspect i.e., {@link Aspect @Aspect} as well as
+     * {@link Around @Around} or {@link Before @Before} / {@link After @After}.
+     */
+    @Test
+    public void loggingAspect_isValid() {
+        Aspect aspect = AnnotationUtils.findAnnotation(LoggingAspect.class, Aspect.class);
+        assertNotNull("LoggingAspect is not annotated with @Aspect", aspect);
+
+        Map<Method, Around> around = PluginUtils.findMethodAnnotation(LoggingAspect.class, Around.class);
+        Map<Method, Before> before = PluginUtils.findMethodAnnotation(LoggingAspect.class, Before.class);
+        Map<Method, After> after = PluginUtils.findMethodAnnotation(LoggingAspect.class, After.class);
+
+        boolean found = !around.isEmpty() || (!before.isEmpty() && !after.isEmpty());
+        assertTrue("LoggingAspect does not contain methods annotated with @Around OR @Before / @After", found);
+    }
+
+    /**
+     * Verifies that the pointcut expression of the {@link LoggingAspect} does not match any method except the
+     * {@link IPluginExecutable#execute()} method.
+     */
+    @Test
+    public void pointcutExpression_matchesCorrectly() {
+        IPluginExecutable executable = PluginUtils.getExecutable(LoggingPluginExecutable.class, LoggingAspect.class);
+        assertTrue("Executable must implement the Advised interface", executable instanceof Advised);
+        Advised advised = (Advised) executable;
+
+        PointcutAdvisor pointcutAdvisor = PluginUtils.getPointcutAdvisor(advised);
+        assertNotNull("PointcutAdvisor not found because there is no pointcut or the pointcut does not match", pointcutAdvisor);
+
+        String expression = PluginUtils.getBestExpression(advised);
+        assertTrue("Pointcut expression must include '" + IPluginExecutable.class.getName() + "'", expression.contains(IPluginExecutable.class.getName()));
+        assertTrue("Pointcut expression must include '" + PluginUtils.EXECUTE_METHOD.getName() + "'", expression.contains(PluginUtils.EXECUTE_METHOD.getName()));
+
+        PointcutExpressionImpl pointcutExpression = PluginUtils.getPointcutExpression(advised);
+        ShadowMatch shadowMatch = pointcutExpression.matchesMethodExecution(PluginUtils.EXECUTE_METHOD);
+        assertTrue("Pointcut does not match IPluginExecute.execute()", shadowMatch.alwaysMatches());
+
+        shadowMatch = pointcutExpression.matchesMethodExecution(PluginUtils.INTERRUPTED_METHOD);
+        assertTrue("Pointcut must not match IPluginExecute.interrupted()", shadowMatch.neverMatches());
+
+        shadowMatch = pointcutExpression.matchesMethodExecution(ReflectionUtils.findMethod(getClass(), PluginUtils.EXECUTE_METHOD.getName()));
+        assertTrue("Pointcut must not match LoggingPluginTest.execute()", shadowMatch.neverMatches());
+    }
+
+    /**
+     * Verifies that the pointcut expression of the LoggingAspect contains the {@link Invisible @Invisible} annotation.
+     */
+    @Test
+    public void pointcutExpression_containsInvisibleAnnotation() {
+        IPluginExecutable executable = PluginUtils.getExecutable(LoggingPluginExecutable.class, LoggingAspect.class);
+        Advised advised = (Advised) executable;
+
+        String expression = PluginUtils.getBestExpression(advised);
+        String annotationName = Invisible.class.getName();
+        assertTrue("Pointcut expression does not contain " + annotationName, expression.contains(annotationName));
+    }
+
+    /**
+     * Verifies that the pointcut expression of the {@link LoggingAspect} does not match any method annotated with
+     * {@link Invisible @Invisible}.
+     */
+    @Test
+    public void pointcutExpression_doesNotMatchInvisible() {
+        IPluginExecutable executable = PluginUtils.getExecutable(LoggingPluginExecutable.class, LoggingAspect.class);
+        Advised advised = (Advised) executable;
+
+        PointcutExpressionImpl pointcutExpression = PluginUtils.getPointcutExpression(advised);
+
+        Method loggingMethod = ReflectionUtils.findMethod(LoggingPluginExecutable.class, PluginUtils.EXECUTE_METHOD.getName());
+        ShadowMatch shadowMatch = pointcutExpression.matchesMethodExecution(loggingMethod);
+        assertTrue("Pointcut does not match LoggingPluginExecutable.execute()", shadowMatch.alwaysMatches());
+
+        Method invisibleMethod = ReflectionUtils.findMethod(InvisiblePluginExecutable.class, PluginUtils.EXECUTE_METHOD.getName());
+        shadowMatch = pointcutExpression.matchesMethodExecution(invisibleMethod);
+        assertTrue("Pointcut matches InvisiblePluginExecutable.execute()", shadowMatch.neverMatches());
+    }
+
+    /**
+     * Tests if the {@link LoggingAspect} uses the {@link java.util.logging.Logger Logger} defined in the plugin.
+     */
+    @Test
+    public void loggingAspect_usesLogger() {
+        IPluginExecutable executable = PluginUtils.getExecutable(LoggingPluginExecutable.class, LoggingAspect.class);
+        Advised advised = (Advised) executable;
+
+        // Add handler end check that there are no events
+        PluginUtils.addBusHandlerIfNecessary(advised);
+        assertEquals("EventBus must be empty", 0, eventBus.count(EventType.INFO));
+
+        // Execute plugin and check that there are 2 events
+        executable.execute();
+        List<Event> events = eventBus.getEvents(EventType.INFO);
+        assertEquals("EventBus must exactly contain 2 INFO events", 2, events.size());
+
+        // Check if the logger contains the correct class name
+        events = eventBus.getEvents(EventType.INFO);
+        for (Event event : events) {
+            assertEquals("Event message must contain the name of the " + LoggingAspect.class.getSimpleName(), LoggingAspect.class.getName(), event.getMessage());
+            assertSame("Event must be logged for " + LoggingPluginExecutable.class.getSimpleName(), LoggingPluginExecutable.class, event.getPluginClass());
+        }
+    }
+
+    /**
+     * Tests if the {@link LoggingAspect} uses {@code System.out} if the plugin does not contain a
+     * {@link java.util.logging.Logger Logger} field.
+     *
+     * @throws IllegalAccessException if {@code System.out} cannot be modified (must not happen)
+     */
+    @Test
+    public void loggingAspect_usesSystemOut() throws IllegalAccessException {
+        // Redirect System.out
+        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+        PrintStream out = PluginUtils.setStaticFinalField(System.class, "out", new PrintStream(byteArrayOutputStream));
+        try {
+            // Execute plugin
+            IPluginExecutable executable = PluginUtils.getExecutable(SystemOutPluginExecutable.class, LoggingAspect.class);
+            assertEquals("EventBus must be empty", 0, eventBus.size());
+            executable.execute();
+            assertEquals("EventBus must exactly contain 2 events", 2, eventBus.size());
+
+            // Verify that the log output contains the class name of the executed plugin
+            String output = byteArrayOutputStream.toString();
+            assertTrue(String.format("Log output must contain %s\n\tbut was%s", SystemOutPluginExecutable.class.getName(), output),
+                    output.contains(SystemOutPluginExecutable.class.getName()));
+        } finally {
+            // Reset System.out
+            PluginUtils.setStaticFinalField(System.class, "out", out);
+        }
+    }
+
+    public void execute() {
+
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/tests/Ass2_4_3Test.java

@@ -0,0 +1,90 @@
+package dst.ass2.aop.tests;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.lang.reflect.Method;
+import java.util.List;
+import java.util.Map;
+
+import dst.ass2.aop.IPluginExecutable;
+import dst.ass2.aop.event.Event;
+import dst.ass2.aop.event.EventBus;
+import dst.ass2.aop.sample.InterruptedPluginExecutable;
+import dst.ass2.aop.util.PluginUtils;
+import org.aspectj.lang.annotation.After;
+import org.aspectj.lang.annotation.Around;
+import org.aspectj.lang.annotation.Aspect;
+import org.aspectj.lang.annotation.Before;
+import org.aspectj.weaver.internal.tools.PointcutExpressionImpl;
+import org.aspectj.weaver.tools.ShadowMatch;
+import org.junit.Test;
+import org.springframework.aop.PointcutAdvisor;
+import org.springframework.aop.framework.Advised;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.util.ReflectionUtils;
+
+import dst.ass2.aop.management.ManagementAspect;
+
+public class Ass2_4_3Test {
+    final EventBus eventBus = EventBus.getInstance();
+
+    @org.junit.Before
+    @org.junit.After
+    public void beforeAndAfter() {
+        eventBus.reset();
+    }
+
+    /**
+     * Verifies that the {@link ManagementAspect} is a valid AspectJ aspect i.e., {@link Aspect @Aspect} as well as
+     * {@link Around @Around} or {@link Before @Before} / {@link After @After}.
+     */
+    @Test
+    public void managementAspect_isValid() {
+        Aspect aspect = AnnotationUtils.findAnnotation(ManagementAspect.class, Aspect.class);
+        assertNotNull("ManagementAspect is not annotated with @Aspect", aspect);
+
+        Map<Method, Around> around = PluginUtils.findMethodAnnotation(ManagementAspect.class, Around.class);
+        Map<Method, Before> before = PluginUtils.findMethodAnnotation(ManagementAspect.class, Before.class);
+        Map<Method, After> after = PluginUtils.findMethodAnnotation(ManagementAspect.class, After.class);
+
+        boolean found = !around.isEmpty() || (!before.isEmpty() && !after.isEmpty());
+        assertEquals("ManagementAspect does not contain methods annotated with @Around OR @Before and @After", true, found);
+    }
+
+    /**
+     * Verifies that the pointcut expression of the {@link ManagementAspect}
+     * does not match any method except the {@link IPluginExecutable#execute()} method.
+     */
+    @Test
+    public void pointcutExpression_matchesCorrectly() {
+        IPluginExecutable executable = PluginUtils.getExecutable(InterruptedPluginExecutable.class, ManagementAspect.class);
+        assertEquals("Executable must implement the Advised interface", true, executable instanceof Advised);
+        Advised advised = (Advised) executable;
+
+        PointcutAdvisor pointcutAdvisor = PluginUtils.getPointcutAdvisor(advised);
+        assertNotNull("PointcutAdvisor not found because there is no pointcut or the pointcut does not match", pointcutAdvisor);
+
+        PointcutExpressionImpl pointcutExpression = PluginUtils.getPointcutExpression(advised);
+        Method interruptedMethod = ReflectionUtils.findMethod(InterruptedPluginExecutable.class, PluginUtils.EXECUTE_METHOD.getName());
+        ShadowMatch shadowMatch = pointcutExpression.matchesMethodExecution(interruptedMethod);
+        assertEquals("Pointcut does not match InterruptedPluginExecutable.execute()", true, shadowMatch.alwaysMatches());
+    }
+
+    /**
+     * Tests if the {@link ManagementAspect} interrupts the plugin after the given timeout.
+     */
+    @Test(timeout = PluginUtils.PLUGIN_TEST_TIMEOUT)
+    public void managementAspect_interruptsCorrectly() {
+        IPluginExecutable executable = PluginUtils.getExecutable(InterruptedPluginExecutable.class, ManagementAspect.class);
+        assertEquals("EventBus must be empty", 0, eventBus.size());
+        executable.execute();
+
+        List<Event> events = eventBus.getEvents();
+        assertEquals("EventBus must contain 2 events", 2, events.size());
+
+        long duration = events.get(1).getTime() - events.get(0).getTime();
+        assertTrue("Plugin was not interrupted 2 seconds after starting it", duration < 3000);
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/tests/Ass2_4_Suite.java

@@ -0,0 +1,13 @@
+package dst.ass2.aop.tests;
+
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+
+@RunWith(Suite.class)
+@Suite.SuiteClasses({
+        Ass2_4_1Test.class,
+        Ass2_4_2Test.class,
+        Ass2_4_3Test.class
+})
+public class Ass2_4_Suite {
+}

ass2-aop/src/test/java/dst/ass2/aop/util/JarUtils.java

@@ -0,0 +1,60 @@
+package dst.ass2.aop.util;
+
+import static org.apache.commons.io.FileUtils.openOutputStream;
+import static org.apache.commons.io.IOUtils.copy;
+import static org.apache.commons.lang3.StringUtils.defaultIfBlank;
+import static org.apache.commons.lang3.StringUtils.join;
+import static org.springframework.util.ClassUtils.CLASS_FILE_SUFFIX;
+import static org.springframework.util.ClassUtils.convertClassNameToResourcePath;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.jar.JarEntry;
+import java.util.jar.JarOutputStream;
+import java.util.zip.ZipOutputStream;
+
+import org.apache.commons.io.input.AutoCloseInputStream;
+import org.springframework.core.io.ClassPathResource;
+
+/**
+ * Builds plugin JARs on demand.
+ *
+ * This class is for internal purposes only.
+ * Note that the {@link #main(String...)} method can be adjusted to create other plugins.
+ */
+public final class JarUtils {
+    private JarUtils() {
+    }
+
+    public static void main(String... args) throws IOException {
+        String path = join(args, " ");
+        File dir = new File(defaultIfBlank(path, "ass2-aop/src/test/resources"));
+
+        createJar(new File(dir, "simple.zip"),
+                "dst.ass2.aop.sample.SimplePluginExecutable"
+        );
+
+        createJar(new File(dir, "all.zip"),
+                "dst.ass2.aop.sample.SimplePluginExecutable",
+                "dst.ass2.aop.sample.IgnoredPluginExecutable"
+        );
+    }
+
+    /**
+     * Creates a new JAR file containing the given classes.
+     *
+     * @param jarFile the destination JAR file
+     * @param classes the classes to add
+     * @throws IOException if an I/O error has occurred
+     */
+    public static void createJar(File jarFile, String... classes) throws IOException {
+        try (JarOutputStream stream = new JarOutputStream(openOutputStream(jarFile))) {
+            stream.setLevel(ZipOutputStream.STORED);
+            for (String clazz : classes) {
+                String path = convertClassNameToResourcePath(clazz) + CLASS_FILE_SUFFIX;
+                stream.putNextEntry(new JarEntry(path));
+                copy(new AutoCloseInputStream(new ClassPathResource(path).getInputStream()), stream);
+            }
+        }
+    }
+}

ass2-aop/src/test/java/dst/ass2/aop/util/PluginUtils.java

@@ -0,0 +1,277 @@
+package dst.ass2.aop.util;
+
+import static org.apache.commons.io.filefilter.FileFileFilter.FILE;
+import static org.apache.commons.io.filefilter.FileFilterUtils.and;
+import static org.apache.commons.io.filefilter.FileFilterUtils.or;
+import static org.apache.commons.io.filefilter.FileFilterUtils.prefixFileFilter;
+import static org.springframework.util.ReflectionUtils.findField;
+import static org.springframework.util.ReflectionUtils.findMethod;
+import static org.springframework.util.ReflectionUtils.getField;
+import static org.springframework.util.ReflectionUtils.makeAccessible;
+
+import java.io.File;
+import java.io.FileFilter;
+import java.io.IOException;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.logging.Handler;
+import java.util.logging.Logger;
+
+import dst.ass2.aop.event.EventBusHandler;
+import org.apache.commons.io.FileUtils;
+import org.aspectj.weaver.internal.tools.PointcutExpressionImpl;
+import org.aspectj.weaver.patterns.Pointcut;
+import org.springframework.aop.Advisor;
+import org.springframework.aop.PointcutAdvisor;
+import org.springframework.aop.aspectj.AbstractAspectJAdvice;
+import org.springframework.aop.aspectj.AspectJExpressionPointcut;
+import org.springframework.aop.aspectj.annotation.AspectJProxyFactory;
+import org.springframework.aop.framework.Advised;
+import org.springframework.aop.support.AopUtils;
+import org.springframework.beans.BeanUtils;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.core.io.ClassPathResource;
+
+import dst.ass2.aop.IPluginExecutable;
+
+/**
+ * Contains some utility methods for plugins.
+ */
+public final class PluginUtils {
+
+    public final static int PLUGIN_TEST_TIMEOUT = 30000;
+
+    public static final File PLUGINS_DIR = new File(
+            FileUtils.getTempDirectoryPath(), "plugins_"
+            + System.currentTimeMillis());
+
+    public static File ALL_FILE;
+    public static File SIMPLE_FILE;
+
+    public static final Method EXECUTE_METHOD = findMethod(
+            IPluginExecutable.class, "execute");
+    public static final Method INTERRUPTED_METHOD = findMethod(
+            IPluginExecutable.class, "interrupted");
+
+    static {
+        try {
+            ALL_FILE = new ClassPathResource("all.zip").getFile();
+            SIMPLE_FILE = new ClassPathResource("simple.zip").getFile();
+        } catch (IOException e) {
+            throw new RuntimeException("Cannot locate plugin in classpath", e);
+        }
+    }
+
+    private PluginUtils() {
+    }
+
+    /**
+     * Modifies the value of a static (final) field and returns the previous
+     * value.
+     *
+     * @param clazz the class containing the static field
+     * @param name the name of the field
+     * @param value the value to set
+     * @return the previous value
+     * @throws IllegalAccessException if the field is inaccessible
+     *                                (should not be the case, since it is set to accessible manually)
+     */
+    @SuppressWarnings("unchecked")
+    public static <T> T setStaticFinalField(Class<?> clazz, String name, T value)
+            throws IllegalAccessException {
+        // Retrieve the desired field
+        Field field = findField(clazz, name);
+        field.setAccessible(true);
+
+        // Remove the final modifier (if necessary)
+        if (Modifier.isFinal(field.getModifiers())) {
+            Field modifiers = findField(field.getClass(), "modifiers");
+            makeAccessible(modifiers);
+            modifiers.set(field, (Integer) modifiers.get(field)
+                    & ~Modifier.FINAL);
+        }
+
+        // Get the current value
+        T current = (T) field.get(null);
+
+        // Set the new value
+        field.set(null, value);
+
+        return current;
+    }
+
+    /**
+     * Creates a new unique {@link File} object within the {@link #PLUGINS_DIR}
+     * directory.
+     *
+     * @return the file
+     */
+    public static File uniqueFile() {
+        return new File(PLUGINS_DIR, "_" + System.nanoTime() + ".jar");
+    }
+
+    /**
+     * Copies the given file to a file in the plugin directory.<br/>
+     *
+     * @throws IOException if the destination file already exists or the file was not copied
+     * @see #uniqueFile()
+     */
+    public static void preparePlugin(File file) throws IOException {
+        File destFile = uniqueFile();
+        if (destFile.exists()) {
+            throw new IOException("Destination file must not exist.");
+        }
+
+        File tempFile = new File(destFile.getParentFile(), "tmp_"
+                + UUID.randomUUID().toString());
+        FileUtils.copyFile(file, tempFile);
+        if (!tempFile.renameTo(destFile) || !destFile.isFile()) {
+            throw new IOException(String.format(
+                    "File '%s' was not copied to '%s'.", file, destFile));
+        }
+    }
+
+    /**
+     * Deletes all plugin JARs copied to the plugin directory.
+     */
+    public static void cleanPluginDirectory() {
+        FileFilter filter = and(FILE,
+                or(prefixFileFilter("_"), prefixFileFilter("tmp_")));
+        System.gc();
+
+        for (File file : PLUGINS_DIR.listFiles(filter)) {
+            file.delete();
+        }
+    }
+
+    /**
+     * Ads a new {@link EventBusHandler} to the logger declared within the given
+     * objects class if necessary.<br/>
+     * This method does nothing if the logger already has an
+     * {@link EventBusHandler} or there is no logger.
+     *
+     * @param obj the object
+     */
+    public static void addBusHandlerIfNecessary(Object obj) {
+        Class<?> targetClass = AopUtils.getTargetClass(obj);
+        Field field = findField(targetClass, null, Logger.class);
+        if (field != null) {
+            makeAccessible(field);
+            Logger logger = (Logger) getField(field, obj);
+            for (Handler handler : logger.getHandlers()) {
+                if (handler instanceof EventBusHandler) {
+                    return;
+                }
+            }
+            logger.addHandler(new EventBusHandler());
+        }
+    }
+
+    /**
+     * Creates a new instance of the given {@link IPluginExecutable} class and
+     * returns a proxy with the AspectJ aspect applied to it.<br/>
+     * If {@code aspectClass} is {@code null}, no aspect is applied.
+     *
+     * @param clazz the plugin class
+     * @param aspectClass the class containing AspectJ definitions
+     * @return proxy of the plugin instance
+     */
+    public static IPluginExecutable getExecutable(
+            Class<? extends IPluginExecutable> clazz, Class<?> aspectClass) {
+        IPluginExecutable target = BeanUtils.instantiateClass(clazz);
+        AspectJProxyFactory factory = new AspectJProxyFactory(target);
+        factory.setProxyTargetClass(true);
+        if (aspectClass != null) {
+            factory.addAspect(BeanUtils.instantiateClass(aspectClass));
+        }
+        return factory.getProxy();
+    }
+
+    /**
+     * Returns the pointcut expression of the given advised proxy.
+     *
+     * @param advised the proxy with the applied aspect
+     * @return the pointcut expression or {@code null} if none was found
+     */
+    public static PointcutExpressionImpl getPointcutExpression(Advised advised) {
+        PointcutAdvisor pointcutAdvisor = getPointcutAdvisor(advised);
+        if (pointcutAdvisor != null) {
+            AspectJExpressionPointcut pointcut = (AspectJExpressionPointcut) pointcutAdvisor
+                    .getPointcut();
+            if (pointcut.getPointcutExpression() instanceof PointcutExpressionImpl) {
+                return (PointcutExpressionImpl) pointcut
+                        .getPointcutExpression();
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Returns the pointcut advisor of the given proxy if its advice part is an
+     * {@link AbstractAspectJAdvice}.
+     *
+     * @param advised the proxy with the applied aspect
+     * @return the pointcut advisor or {@code null} if there is no AspectJ pointcut advisor applied
+     */
+    public static PointcutAdvisor getPointcutAdvisor(Advised advised) {
+        for (Advisor advisor : advised.getAdvisors()) {
+            if (advisor instanceof PointcutAdvisor
+                    && advisor.getAdvice() instanceof AbstractAspectJAdvice) {
+                return (PointcutAdvisor) advisor;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Attempts to resolve all parts of the pointcut expression of the aspect
+     * applied to the given proxy.
+     *
+     * @param advised the proxy with the applied aspect
+     * @return a string representation of this pointcut expression
+     * @see #getPointcutExpression(org.springframework.aop.framework.Advised)
+     * @see #getPointcutAdvisor(org.springframework.aop.framework.Advised)
+     */
+    public static String getBestExpression(Advised advised) {
+        PointcutExpressionImpl pointcutExpression = getPointcutExpression(advised);
+        if (pointcutExpression != null) {
+            Pointcut underlyingPointcut = pointcutExpression
+                    .getUnderlyingPointcut();
+            if (findMethod(underlyingPointcut.getClass(), "toString")
+                    .getDeclaringClass() != Object.class) {
+                return underlyingPointcut.toString();
+            }
+            return pointcutExpression.getPointcutExpression();
+        }
+        PointcutAdvisor advisor = getPointcutAdvisor(advised);
+        AspectJExpressionPointcut pointcut = (AspectJExpressionPointcut) advisor
+                .getPointcut();
+        return pointcut.getExpression();
+    }
+
+    /**
+     * Finds all public methods of the given class annotated with a certain
+     * annotation.
+     *
+     * @param clazz the class
+     * @param annotationType the annotation to search for
+     * @return methods annotated with the given annotation
+     */
+    public static <A extends Annotation> Map<Method, A> findMethodAnnotation(
+            Class<?> clazz, Class<A> annotationType) {
+        Map<Method, A> map = new HashMap<Method, A>();
+        for (Method method : clazz.getDeclaredMethods()) {
+            A annotation = AnnotationUtils.findAnnotation(method,
+                    annotationType);
+            if (annotation != null) {
+                map.put(method, annotation);
+            }
+        }
+        return map;
+    }
+}