Add template for assignment 2

ass2-ioc/src/main/java/dst/ass2/ioc/di/IObjectContainer.java

@@ -0,0 +1,27 @@
+package dst.ass2.ioc.di;
+
+import dst.ass2.ioc.di.annotation.Property;
+
+import java.util.Properties;
+
+public interface IObjectContainer {
+
+    /**
+     * Returns the (mutable) data structure holding property values that can be injected via the
+     * {@link Property} annotation.
+     *
+     * @return A mutable Properties object
+     */
+    Properties getProperties();
+
+    /**
+     * Returns a container-managed object of the given type.
+     *
+     * @param type the type of object
+     * @param <T>  the class type
+     * @return the object
+     * @throws InjectionException throw the concrete InjectionException as specified in the assignment
+     */
+    <T> T getObject(Class<T> type) throws InjectionException;
+
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/IObjectContainerFactory.java

@@ -0,0 +1,17 @@
+package dst.ass2.ioc.di;
+
+import dst.ass2.ioc.di.annotation.Property;
+
+import java.util.Properties;
+
+public interface IObjectContainerFactory {
+
+    /**
+     * Creates a new IObjectContainer instance that uses the given properties for injecting
+     * {@link Property} instances.
+     *
+     * @param properties a Properties object
+     * @return a new IObjectContainer instance
+     */
+    IObjectContainer newObjectContainer(Properties properties);
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/InjectionException.java

@@ -0,0 +1,18 @@
+package dst.ass2.ioc.di;
+
+public class InjectionException extends RuntimeException {
+    private static final long serialVersionUID = 1L;
+
+    public InjectionException(String message) {
+        super(message);
+    }
+
+    public InjectionException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public InjectionException(Throwable cause) {
+        super(cause);
+    }
+
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/InvalidDeclarationException.java

@@ -0,0 +1,15 @@
+package dst.ass2.ioc.di;
+
+public class InvalidDeclarationException extends InjectionException {
+    public InvalidDeclarationException(String message) {
+        super(message);
+    }
+
+    public InvalidDeclarationException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public InvalidDeclarationException(Throwable cause) {
+        super(cause);
+    }
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/ObjectCreationException.java

@@ -0,0 +1,15 @@
+package dst.ass2.ioc.di;
+
+public class ObjectCreationException extends InjectionException {
+    public ObjectCreationException(String message) {
+        super(message);
+    }
+
+    public ObjectCreationException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public ObjectCreationException(Throwable cause) {
+        super(cause);
+    }
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/TypeConversionException.java

@@ -0,0 +1,15 @@
+package dst.ass2.ioc.di;
+
+public class TypeConversionException extends InjectionException {
+    public TypeConversionException(String message) {
+        super(message);
+    }
+
+    public TypeConversionException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public TypeConversionException(Throwable cause) {
+        super(cause);
+    }
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/annotation/Component.java

@@ -0,0 +1,21 @@
+package dst.ass2.ioc.di.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Marks a class to be container managed.
+ */
+// TODO: add correct retention policy and target type
+public @interface Component {
+
+    /**
+     * The component can either be marked to be a singleton or a prototype via the {@link Scope} enum. The default scope
+     * is singleton.
+     *
+     * @return the scope
+     */
+    Scope scope() default Scope.SINGLETON;
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/annotation/Initialize.java

@@ -0,0 +1,15 @@
+package dst.ass2.ioc.di.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Initialize marks a method to be invoked by the container after it has been constructed and all dependencies and
+ * properties have been injected.
+ */
+// TODO: add correct retention policy and target type
+public @interface Initialize {
+
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/annotation/Inject.java

@@ -0,0 +1,28 @@
+package dst.ass2.ioc.di.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Inject marks a field in a class to be autowired by the container.
+ */
+// TODO: add correct retention policy and target type
+public @interface Inject {
+
+    /**
+     * Marks whether the dependency is required or not.
+     *
+     * @return a boolean value
+     */
+    boolean optional() default false;
+
+    /**
+     * Explicitly states the class that should be injected by the container into this field. If the target type is Void,
+     * then we assume the targetType is not set, and the container uses the declared field type instead.
+     *
+     * @return a class
+     */
+    Class<?> targetType() default Void.class;
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/annotation/Property.java

@@ -0,0 +1,20 @@
+package dst.ass2.ioc.di.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * A property injects the value of a {@link java.util.Properties} object into a field based on a key.
+ */
+// TODO: add correct retention policy and target type
+public @interface Property {
+
+    /**
+     * The key to look up in the container's Properties object.
+     *
+     * @return a key
+     */
+    String value();
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/annotation/Scope.java

@@ -0,0 +1,9 @@
+package dst.ass2.ioc.di.annotation;
+
+/**
+ * The scope of a {@link Component}.
+ */
+public enum Scope {
+    SINGLETON,
+    PROTOTYPE
+}

ass2-ioc/src/main/java/dst/ass2/ioc/di/impl/ObjectContainerFactory.java

@@ -0,0 +1,16 @@
+package dst.ass2.ioc.di.impl;
+
+import dst.ass2.ioc.di.IObjectContainer;
+import dst.ass2.ioc.di.IObjectContainerFactory;
+
+import java.util.Properties;
+
+public final class ObjectContainerFactory implements IObjectContainerFactory {
+
+    @Override
+    public IObjectContainer newObjectContainer(Properties properties) {
+        // TODO: implement
+        return null;
+    }
+
+}

ass2-ioc/src/main/java/dst/ass2/ioc/lock/Lock.java

@@ -0,0 +1,21 @@
+package dst.ass2.ioc.lock;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Marks a method to be executed by acquiring a named lock.
+ */
+// TODO: add correct retention policy and target type
+public @interface Lock {
+
+    /**
+     * The name of the container managed lock.
+     *
+     * @return a name
+     */
+    String value();
+
+}

ass2-ioc/src/main/java/dst/ass2/ioc/lock/LockingInjector.java

@@ -0,0 +1,19 @@
+package dst.ass2.ioc.lock;
+
+import java.lang.instrument.ClassFileTransformer;
+import java.lang.instrument.IllegalClassFormatException;
+import java.security.ProtectionDomain;
+
+public class LockingInjector implements ClassFileTransformer {
+
+    @Override
+    public byte[] transform(ClassLoader loader, String className,
+                            Class<?> classBeingRedefined, ProtectionDomain protectionDomain,
+                            byte[] classfileBuffer) throws IllegalClassFormatException {
+
+        // TODO transform all @Lock annotated methods of classes with a @Component annotation
+
+        return classfileBuffer;
+    }
+
+}

ass2-ioc/src/main/java/dst/ass2/ioc/lock/LockingInjectorAgent.java

@@ -0,0 +1,11 @@
+package dst.ass2.ioc.lock;
+
+import java.lang.instrument.Instrumentation;
+
+public class LockingInjectorAgent {
+
+    public static void premain(String args, Instrumentation inst) {
+        // TODO
+    }
+
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/Ass2_2_1_Suite.java

@@ -0,0 +1,19 @@
+package dst.ass2.ioc.tests;
+
+import dst.ass2.ioc.tests.di.DependencyInjectionTest;
+import dst.ass2.ioc.tests.di.HierarchyTest;
+import dst.ass2.ioc.tests.di.InitializeTest;
+import dst.ass2.ioc.tests.di.PropertyInjectionTest;
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+
+@RunWith(Suite.class)
+@Suite.SuiteClasses({
+        DependencyInjectionTest.class,
+        PropertyInjectionTest.class,
+        HierarchyTest.class,
+        InitializeTest.class
+})
+public class Ass2_2_1_Suite {
+    // suite
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/Ass2_2_2_Suite.java

@@ -0,0 +1,13 @@
+package dst.ass2.ioc.tests;
+
+import dst.ass2.ioc.tests.lock.LockingTest;
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+
+@RunWith(Suite.class)
+@Suite.SuiteClasses({
+        LockingTest.class
+})
+public class Ass2_2_2_Suite {
+    // suite
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/di/CustomInitializeTest.java

@@ -0,0 +1,10 @@
+package dst.ass2.ioc.tests.di;
+
+public class CustomInitializeTest {
+
+    /*
+     * TODO: In cases where the object hierarchy has multiple methods annotated with @Initialize or overwrites
+     *  previously annotated methods, you should come up with your own behavior. Document the behavior with at least two
+     *  unit tests.
+     */
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/di/DependencyInjectionTest.java

@@ -0,0 +1,218 @@
+package dst.ass2.ioc.tests.di;
+
+
+import dst.ass2.ioc.di.IObjectContainer;
+import dst.ass2.ioc.di.IObjectContainerFactory;
+import dst.ass2.ioc.di.InjectionException;
+import dst.ass2.ioc.di.InvalidDeclarationException;
+import dst.ass2.ioc.di.annotation.Component;
+import dst.ass2.ioc.di.annotation.Inject;
+import dst.ass2.ioc.di.annotation.Scope;
+import dst.ass2.ioc.di.impl.ObjectContainerFactory;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Properties;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+
+public class DependencyInjectionTest {
+
+    private IObjectContainerFactory factory;
+    private IObjectContainer container;
+
+    @Before
+    public void setUp() {
+        factory = new ObjectContainerFactory();
+        container = factory.newObjectContainer(new Properties());
+
+        if (container == null) {
+            throw new NullPointerException("ObjectContainerFactory did not return an ObjectContainer instance");
+        }
+    }
+
+    @Component
+    public static class SimpleSingleton {
+        public String someValue;
+
+        public SimpleSingleton() {
+            // just to verify that the constructor has been called correctly
+            this.someValue = "42";
+        }
+    }
+
+    public static class NotAComponentClass {
+        // a plain class shouldn't be autowired
+
+        @Inject
+        SimpleSingleton singleton;
+    }
+
+    @Test(expected = InvalidDeclarationException.class)
+    public void getObject_onNotAnnotatedClass_throwsException() {
+        container.getObject(NotAComponentClass.class);
+    }
+
+
+    @Component
+    public static abstract class AbstractComponentClass {
+        // abstract classes can't be instantiated
+    }
+
+    @Test(expected = InjectionException.class)
+    public void getObject_onAbstractClass_throwsException() throws Exception {
+        container.getObject(AbstractComponentClass.class);
+    }
+
+    @Test
+    public void getObject_onSimpleSingleton_createsObjectCorrectly() {
+        var object = container.getObject(SimpleSingleton.class);
+        assertNotNull(object);
+        assertThat(object, instanceOf(SimpleSingleton.class));
+        assertEquals("constructor was not called correctly", "42", object.someValue);
+    }
+
+    @Test
+    public void getObject_onSimpleSingleton_returnsSameObject() {
+        var object1 = container.getObject(SimpleSingleton.class);
+        var object2 = container.getObject(SimpleSingleton.class);
+
+        assertNotNull(object1);
+        assertNotNull(object2);
+        assertSame(object1, object2);
+    }
+
+    @Test
+    public void getObject_onDifferentContainer_returnsDifferentObject() {
+        var container1 = factory.newObjectContainer(new Properties());
+        var object1 = container1.getObject(SimpleSingleton.class);
+
+        var container2 = factory.newObjectContainer(new Properties());
+        var object2 = container2.getObject(SimpleSingleton.class);
+
+        assertNotNull(object1);
+        assertNotNull(object2);
+        assertNotSame(object1, object2);
+    }
+
+    @Component(scope = Scope.PROTOTYPE)
+    public static class SimplePrototype {
+
+        static final AtomicInteger COUNTER = new AtomicInteger(0);
+
+        public int cnt;
+
+        public SimplePrototype() {
+            // just to verify that the constructor has been called correctly
+            cnt = SimplePrototype.COUNTER.incrementAndGet();
+        }
+    }
+
+    @Test
+    public void getObject_onSimplePrototype_returnsDifferentObjects() {
+        SimplePrototype.COUNTER.set(0);
+        var object1 = container.getObject(SimplePrototype.class);
+        var object2 = container.getObject(SimplePrototype.class);
+
+        assertNotNull(object1);
+        assertNotNull(object2);
+        assertNotSame(object1, object2);
+
+        assertEquals(1, object1.cnt);
+        assertEquals(2, object2.cnt);
+    }
+
+    @Component(scope = Scope.PROTOTYPE)
+    public static class CompositePrototype {
+
+        @Inject
+        SimpleSingleton simpleSingleton;
+    }
+
+    @Test
+    public void getObject_onCompositePrototype_createsObjectCorrectly() {
+        var object = container.getObject(CompositePrototype.class);
+        assertNotNull(object.simpleSingleton);
+    }
+
+    @Test
+    public void getObject_onCompositePrototype_injectsPreviouslyCreatedSingleton() {
+        var singleton = container.getObject(SimpleSingleton.class);
+
+        var object = container.getObject(CompositePrototype.class);
+        assertNotNull(object.simpleSingleton);
+
+        assertSame("autowire should use already container managed singletons", singleton, object.simpleSingleton);
+    }
+
+    @Component
+    public static class CompositeSingleton {
+        @Inject
+        SimpleSingleton simpleSingleton;
+    }
+
+    @Test
+    public void getObject_onCompositeSingleton_createsObjectGraphCorrectly() {
+        var object = container.getObject(CompositeSingleton.class);
+
+        assertNotNull(object);
+        assertThat(object, instanceOf(CompositeSingleton.class));
+
+        assertNotNull("dependency of CompositeSingleton not initialized", object.simpleSingleton);
+        assertNotNull("dependency of CompositeSingleton not initialized correctly", object.simpleSingleton.someValue);
+    }
+
+    public interface IService {
+        int getSomeValue();
+    }
+
+    @Component
+    public static class ServiceImpl implements IService {
+        private int someValue;
+
+        public ServiceImpl() {
+            someValue = 42;
+        }
+
+        @Override
+        public int getSomeValue() {
+            return someValue;
+        }
+    }
+
+    @Component
+    public static class ServiceUser {
+        @Inject(targetType = ServiceImpl.class)
+        IService service;
+    }
+
+    @Test
+    public void getObject_usingTargetType_createsGraphCorrectly() throws Exception {
+        var object = container.getObject(ServiceUser.class);
+
+        assertNotNull(object);
+        assertNotNull("dependency of ServiceUser not initialized", object.service);
+        assertThat("dependency of ServiceUser not initialized correctly", object.service, instanceOf(ServiceImpl.class));
+        assertEquals("dependency of ServiceUser not initialized correctly", 42, object.service.getSomeValue());
+    }
+
+    @Component
+    public static class InvalidServiceUser {
+        // trying to inject an existing but invalid type (a SimplePrototype is not an IService)
+        @Inject(targetType = SimplePrototype.class)
+        IService service;
+    }
+
+    @Test(expected = InvalidDeclarationException.class)
+    public void getObject_onInvalidTargetType_throwsException() {
+        container.getObject(InvalidServiceUser.class);
+    }
+
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/di/HierarchyTest.java

@@ -0,0 +1,125 @@
+package dst.ass2.ioc.tests.di;
+
+import dst.ass2.ioc.di.IObjectContainer;
+import dst.ass2.ioc.di.IObjectContainerFactory;
+import dst.ass2.ioc.di.annotation.Component;
+import dst.ass2.ioc.di.annotation.Inject;
+import dst.ass2.ioc.di.impl.ObjectContainerFactory;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Properties;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+
+
+public class HierarchyTest {
+
+    private IObjectContainerFactory factory;
+    private IObjectContainer container;
+
+    @Before
+    public void setUp() throws Exception {
+        factory = new ObjectContainerFactory();
+        container = factory.newObjectContainer(new Properties());
+    }
+
+    @Component
+    public static class SimpleSingleton {
+        public String someValue;
+
+        public SimpleSingleton() {
+            // just to verify that the constructor has been called correctly
+            this.someValue = "42";
+        }
+    }
+
+    public static abstract class AbstractComponent {
+        @Inject
+        protected SimpleSingleton superSingleton;
+    }
+
+    @Component
+    public static class ConcreteComponent extends AbstractComponent {
+        @Inject
+        private SimpleSingleton privateSingleton;
+
+        public SimpleSingleton getSuperSingleton() {
+            return superSingleton;
+        }
+
+        public SimpleSingleton getPrivateSingleton() {
+            return privateSingleton;
+        }
+    }
+
+    @Test
+    public void getObject_injectsDependencyOfSuperClassCorrectly() throws Exception {
+        ConcreteComponent component = container.getObject(ConcreteComponent.class);
+
+        assertNotNull("getObject returned null", component);
+        assertNotNull("Dependency of superclass was not injected", component.getSuperSingleton());
+        assertNotNull("Private dependency was not injected", component.getPrivateSingleton());
+        assertSame("Multiple singleton instances", component.getSuperSingleton(), component.getPrivateSingleton());
+    }
+
+    @Component
+    public static class ClassA {
+        @Inject
+        SimpleSingleton singletonA;
+    }
+
+    @Component
+    public static class ClassB extends ClassA {
+
+        @Inject
+        SimpleSingleton singletonB;
+
+        @Inject
+        ClassD classD;
+    }
+
+    @Component
+    public static class ClassC {
+
+        @Inject
+        SimpleSingleton singletonC;
+    }
+
+    @Component
+    public static class ClassD extends ClassC {
+
+        @Inject
+        SimpleSingleton singletonD;
+    }
+
+    /**
+     * Tests the following hierarchy. Getting first D then B should should inject the previously created D into B.
+     *
+     * +-------+      +-------+
+     * |   A   |      |   C   |
+     * +-------+      +-------+
+     *     ^ is a         ^ is a
+     *     |              |
+     * +-------+ uses +-------+
+     * |   B   | ---> |   D   |
+     * +-------+      +-------+
+     */
+    @Test
+    public void getObject_initializesHierarchyCorrectly() throws Exception {
+        ClassD d = container.getObject(ClassD.class);
+
+        assertNotNull("getObject returned null for ClassD", d);
+        assertNotNull("ClassD dependency was not injected", d.singletonD);
+        assertNotNull("ClassC dependency was not injected when instantiating ClassD", d.singletonC);
+
+        ClassB b = container.getObject(ClassB.class);
+        assertNotNull("getObject returned null for ClassB", b);
+        assertNotNull("ClassB dependency was not injected", b.singletonB);
+        assertNotNull("ClassA dependency was not injected when instantiating ClassB", b.singletonA);
+
+        assertNotNull("ClassD dependency was not injected into ClassB", b.classD);
+        assertSame("Container did not re-use already initialized ClassD instance", b.classD, d);
+    }
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/di/InitializeTest.java

@@ -0,0 +1,114 @@
+package dst.ass2.ioc.tests.di;
+
+import dst.ass2.ioc.di.IObjectContainer;
+import dst.ass2.ioc.di.IObjectContainerFactory;
+import dst.ass2.ioc.di.annotation.Component;
+import dst.ass2.ioc.di.annotation.Initialize;
+import dst.ass2.ioc.di.annotation.Inject;
+import dst.ass2.ioc.di.impl.ObjectContainerFactory;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Properties;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+public class InitializeTest {
+
+    private IObjectContainerFactory factory;
+    private IObjectContainer container;
+
+    @Before
+    public void setUp() {
+        factory = new ObjectContainerFactory();
+        container = factory.newObjectContainer(new Properties());
+
+        if (container == null) {
+            throw new NullPointerException("ObjectContainerFactory did not return an ObjectContainer instance");
+        }
+    }
+
+    @Component
+    public static class ComponentClass {
+
+        private AtomicInteger initializeCalls = new AtomicInteger(0);
+
+        @Initialize
+        public void myInitMethod() {
+            initializeCalls.incrementAndGet();
+        }
+
+        public int getInitializeCalls() {
+            return initializeCalls.get();
+        }
+    }
+
+    @Test
+    public void getObject_runsInitializeMethodCorrectly() throws Exception {
+        ComponentClass component = container.getObject(ComponentClass.class);
+        assertEquals("expected exactly one call to myInitMethod", 1, component.getInitializeCalls());
+    }
+
+    @Test
+    public void getObject_runsInitializeMethodOnlyOnce() throws Exception {
+        ComponentClass component = container.getObject(ComponentClass.class);
+        assertEquals("expected exactly one call to myInitMethod", 1, component.getInitializeCalls());
+
+        component = container.getObject(ComponentClass.class);
+        assertEquals("expected exactly one call to myInitMethod", 1, component.getInitializeCalls());
+    }
+
+    @Component
+    public static class AnotherComponentClass {
+
+        @Inject
+        private ComponentClass dependency;
+
+        boolean wasNull;
+
+        @Initialize
+        public void myOtherInitMethod() {
+            this.wasNull = dependency == null;
+        }
+
+        public ComponentClass getDependency() {
+            return dependency;
+        }
+    }
+
+    @Test
+    public void getObject_runsInitializeMethodAfterInjection() throws Exception {
+        AnotherComponentClass component = container.getObject(AnotherComponentClass.class);
+        assertFalse("Expected dependency to be injected before calls to @Initialize", component.wasNull);
+    }
+
+    @Test
+    public void getObject_runsInitializeMethodOfDependencyCorrectly() throws Exception {
+        AnotherComponentClass component = container.getObject(AnotherComponentClass.class);
+        assertEquals("expected exactly one call to myInitMethod", 1, component.getDependency().getInitializeCalls());
+    }
+
+    @Component
+    public static class ComponentWithPrivateInitMethod {
+
+        private AtomicInteger initializeCalls = new AtomicInteger(0);
+
+        @Initialize
+        private void myPrivateInitMethod() {
+            initializeCalls.incrementAndGet();
+        }
+
+        public int getInitializeCalls() {
+            return initializeCalls.get();
+        }
+    }
+
+    @Test
+    public void getObject_runsPrivateInitializeMethodCorrectly() throws Exception {
+        ComponentWithPrivateInitMethod component = container.getObject(ComponentWithPrivateInitMethod.class);
+        assertEquals("expected exactly one call to myPrivateInitMethod", 1, component.getInitializeCalls());
+    }
+
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/di/PropertyInjectionTest.java

@@ -0,0 +1,268 @@
+package dst.ass2.ioc.tests.di;
+
+import dst.ass2.ioc.di.IObjectContainerFactory;
+import dst.ass2.ioc.di.ObjectCreationException;
+import dst.ass2.ioc.di.TypeConversionException;
+import dst.ass2.ioc.di.annotation.Component;
+import dst.ass2.ioc.di.annotation.Property;
+import dst.ass2.ioc.di.annotation.Scope;
+import dst.ass2.ioc.di.impl.ObjectContainerFactory;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Properties;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+import static org.hamcrest.CoreMatchers.allOf;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class PropertyInjectionTest {
+
+    private IObjectContainerFactory factory;
+
+    @Before
+    public void setUp() {
+        factory = new ObjectContainerFactory();
+    }
+
+    @Component
+    static class StringPropertyClass {
+        @Property("my_string")
+        String value;
+    }
+
+    @Test
+    public void simple_string_value_injection() {
+        var properties = new Properties();
+        properties.setProperty("my_string", "my string value");
+        var container = factory.newObjectContainer(properties);
+
+        StringPropertyClass obj = container.getObject(StringPropertyClass.class);
+        assertNotNull("getObject(StringPropertyClass.class) returned null", obj);
+        assertEquals("my string value", obj.value);
+    }
+
+    @Test(expected = ObjectCreationException.class)
+    public void wireMissingProperty_throwsException() {
+        var container = factory.newObjectContainer(new Properties());
+        container.getObject(StringPropertyClass.class);
+    }
+
+    @Component
+    static class IntegerPropertyClass {
+        @Property("my_integer")
+        Integer value;
+    }
+
+    @Test
+    public void simple_integer_value_injection() {
+        var properties = new Properties();
+        properties.setProperty("my_integer", "42");
+        var container = factory.newObjectContainer(properties);
+
+        IntegerPropertyClass obj = container.getObject(IntegerPropertyClass.class);
+        assertNotNull("getObject(IntegerPropertyClass.class) returned null", obj);
+        assertEquals(Integer.valueOf(42), obj.value);
+    }
+
+    @Test(expected = TypeConversionException.class)
+    public void wireInvalidPropertyType_throwsException() {
+        var properties = new Properties();
+        properties.setProperty("my_integer", "fourtytwo");
+        var container = factory.newObjectContainer(properties);
+
+        IntegerPropertyClass obj = container.getObject(IntegerPropertyClass.class);
+        assertNotNull("getObject(IntegerPropertyClass.class) returned null", obj);
+        assertEquals(Integer.valueOf(42), obj.value);
+    }
+
+    @Component
+    static class IntegerPrimitivePropertyClass {
+        @Property("my_integer")
+        int value;
+    }
+
+    @Test
+    public void simple_integer_primitive_value_injection() {
+        var properties = new Properties();
+        properties.setProperty("my_integer", "42");
+        var container = factory.newObjectContainer(properties);
+
+        IntegerPrimitivePropertyClass obj = container.getObject(IntegerPrimitivePropertyClass.class);
+        assertNotNull("getObject(IntegerPrimitivePropertyClass.class) returned null", obj);
+        assertEquals(42, obj.value);
+    }
+
+    @Component
+    static class MultiplePropertyClass {
+        @Property("my_string")
+        String stringValue;
+
+        @Property("my_integer")
+        int intValue;
+
+        @Property("my_integer")
+        Integer integerValue;
+
+        @Property("my_float")
+        Float floatValue;
+    }
+
+    @Test
+    public void simple_multiple_property_injection() {
+        var properties = new Properties();
+        properties.setProperty("my_string", "my string value");
+        properties.setProperty("my_integer", "42");
+        properties.setProperty("my_float", "3.14");
+        var container = factory.newObjectContainer(properties);
+
+        MultiplePropertyClass obj = container.getObject(MultiplePropertyClass.class);
+        assertNotNull("getObject(MultiplePropertyClass.class) returned null", obj);
+
+        assertEquals("my string value", obj.stringValue);
+        assertEquals(42, obj.intValue);
+        assertEquals(Integer.valueOf(42), obj.integerValue);
+        assertEquals(Float.valueOf(3.14f), obj.floatValue);
+    }
+
+    @Component
+    static class InheritedMultiplePropertyClass extends MultiplePropertyClass {
+        @Property("my_float")
+        Float theSameFloatValue;
+    }
+
+    @Test
+    public void multiple_property_injection_with_inheritance() {
+        var properties = new Properties();
+        properties.setProperty("my_string", "my string value");
+        properties.setProperty("my_integer", "42");
+        properties.setProperty("my_float", "3.14");
+        var container = factory.newObjectContainer(properties);
+
+        InheritedMultiplePropertyClass obj = container.getObject(InheritedMultiplePropertyClass.class);
+        assertNotNull("getObject(InheritedMultiplePropertyClass.class) returned null", obj);
+
+        assertEquals(Float.valueOf(3.14f), obj.theSameFloatValue);
+
+        // inherited values
+        assertEquals("Property not set correctly through inheritance", "my string value", obj.stringValue);
+        assertEquals("Property not set correctly through inheritance", 42, obj.intValue);
+        assertEquals("Property not set correctly through inheritance", Integer.valueOf(42), obj.integerValue);
+        assertEquals("Property not set correctly through inheritance", Float.valueOf(3.14f), obj.floatValue);
+    }
+
+    @Component(scope = Scope.PROTOTYPE)
+    static class PrototypePropertyClass {
+
+        @Property("my_string")
+        String stringValue;
+
+    }
+
+    @Test
+    public void getPrototypeObject_usesLatestPropertyValue() {
+        Properties properties = new Properties();
+        properties.setProperty("my_string", "initial value");
+        var container = factory.newObjectContainer(properties);
+
+        var object1 = container.getObject(PrototypePropertyClass.class);
+        assertEquals("initial value", object1.stringValue);
+
+        // Properties returned by IObjectContainerFactory should be mutable
+        container.getProperties().setProperty("my_string", "changed value");
+
+        var object2 = container.getObject(PrototypePropertyClass.class);
+        assertEquals("properties should be mutable", "changed value", object2.stringValue);
+        assertEquals("initial value", object1.stringValue);
+    }
+
+    @SuppressWarnings("unused")
+    @Component
+    static class ManyValuesClass {
+        @Property("my_string")
+        String stringValue01;
+        @Property("my_integer")
+        Integer value01;
+        @Property("my_integer")
+        Integer value02;
+        @Property("my_integer")
+        Integer value03;
+        @Property("my_integer")
+        Integer value04;
+        @Property("my_integer")
+        Integer value05;
+        @Property("my_string")
+        String stringValue02;
+        @Property("my_integer")
+        Integer value06;
+        @Property("my_integer")
+        Integer value07;
+        @Property("my_integer")
+        Integer value08;
+        @Property("my_integer")
+        Integer value09;
+        @Property("my_integer")
+        Integer value10;
+        @Property("my_string")
+        String stringValue03;
+        @Property("my_integer")
+        Integer value11;
+        @Property("my_integer")
+        Integer value12;
+        @Property("my_integer")
+        Integer value13;
+        @Property("my_integer")
+        Integer value14;
+        @Property("my_integer")
+        Integer value15;
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public void mutatePropertiesConcurrently_verifyThreadSafety() throws Exception {
+        var container = factory.newObjectContainer(new Properties());
+
+        Properties properties = container.getProperties();
+        properties.setProperty("my_integer", "1");
+        properties.setProperty("my_string", "some string value");
+
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        CountDownLatch latch = new CountDownLatch(10);
+
+        executor.execute(() -> {
+            for (int i = 0; i < 100000; i++) {
+                latch.countDown();
+                properties.setProperty("my_integer", Integer.toString(i));
+            }
+        });
+        Future<ManyValuesClass> getObject = executor.submit(() -> {
+            latch.await(); // wait until the property set loop has started and warmed up
+            return container.getObject(ManyValuesClass.class);
+        });
+
+        ManyValuesClass object = getObject.get();
+        executor.shutdown();
+        executor.awaitTermination(2, TimeUnit.SECONDS);
+        executor.shutdownNow();
+
+        assertNotEquals("updated property value was not used", Integer.valueOf(1), object.value01);
+        assertThat("property values are inconsistent indicating non-thread-safe property injection",
+                object.value01, allOf(
+                        is(object.value01), is(object.value02), is(object.value03), is(object.value04),
+                        is(object.value05), is(object.value06), is(object.value07), is(object.value08),
+                        is(object.value09), is(object.value10), is(object.value11), is(object.value12),
+                        is(object.value13), is(object.value14), is(object.value15)
+                ));
+
+    }
+
+
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/lock/LockingTest.java

@@ -0,0 +1,434 @@
+package dst.ass2.ioc.tests.lock;
+
+import dst.ass2.ioc.di.annotation.Component;
+import dst.ass2.ioc.lock.Lock;
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ConcurrentModificationException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.Semaphore;
+
+
+public class LockingTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(LockingTest.class);
+
+    @Rule
+    public ThreadPoolResource executor = new ThreadPoolResource(2);
+
+    /**
+     * This class simulates the use of a shared resource (the semaphore). If the resource is already acquired
+     * by some other thread, then a {@link ConcurrentModificationException} is thrown. We use this behavior to test
+     * various scenarios (whether mutex access is guaranteed when the @Lock value refers to the same lock).
+     */
+    @Component
+    public static class SimpleLockManaged {
+
+        public Semaphore semaphore;
+
+        public SimpleLockManaged(Semaphore semaphore) {
+            this.semaphore = semaphore;
+        }
+
+        @Lock("my_lock")
+        public void useResource() {
+            useResourceImpl();
+        }
+
+        @Lock("my_other_lock")
+        public void useResourceSomeMore() {
+            useResourceImpl();
+        }
+
+        private void useResourceImpl() {
+            LOG.info("{} trying to acquire semaphore", this);
+            boolean acquired = semaphore.tryAcquire();
+
+            if (!acquired) {
+                LOG.info("{} failed to acquire semaphore", this);
+                throw new ConcurrentModificationException("Semaphore was acquired concurrently");
+            }
+
+            // hold the permit for a few ms
+            try {
+                LOG.info("{} holding permit for 500ms", this);
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            } finally {
+                LOG.info("{} releasing semaphore", this);
+                semaphore.release();
+            }
+        }
+    }
+
+    @Test
+    public void mutexTest_onSameClassAndObject_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        SimpleLockManaged lockManaged = new SimpleLockManaged(semaphore);
+
+        Future<?> r1 = executor.submit(lockManaged::useResource);
+        Future<?> r2 = executor.submit(lockManaged::useResource);
+
+        try {
+            r1.get();
+            r2.get();
+        } catch (ExecutionException e) {
+            if (e.getCause() instanceof ConcurrentModificationException) {
+                throw new AssertionError("Access to shared resource was not mutually exclusive as required", e);
+            } else {
+                throw e;
+            }
+        }
+    }
+
+    @Test
+    public void mutexTest_onSameClassButDifferentObject_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        SimpleLockManaged lockManaged1 = new SimpleLockManaged(semaphore);
+        SimpleLockManaged lockManaged2 = new SimpleLockManaged(semaphore);
+
+        Future<?> r1 = executor.submit(lockManaged1::useResource);
+        Future<?> r2 = executor.submit(lockManaged2::useResource);
+
+        try {
+            r1.get();
+            r2.get();
+        } catch (ExecutionException e) {
+            if (e.getCause() instanceof ConcurrentModificationException) {
+                throw new AssertionError("Access to shared resource was not mutually exclusive as required", e);
+            } else {
+                throw e;
+            }
+        }
+    }
+
+    @Test
+    public void nonMutexTest_onSameClassAndObject_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        SimpleLockManaged lockManaged = new SimpleLockManaged(semaphore);
+
+        Future<?> r1 = executor.submit(lockManaged::useResource);
+        Future<?> r2 = executor.submit(lockManaged::useResourceSomeMore);
+
+        try {
+            r1.get();
+            r2.get();
+            throw new AssertionError("Different locks should allow concurrent access to resources");
+        } catch (ExecutionException e) {
+            if (!(e.getCause() instanceof ConcurrentModificationException)) {
+                throw e;
+            }
+            // we expected a concurrent modification exception here
+        }
+
+    }
+
+    @Test
+    public void nonMutexTest_onSameClassButDifferentObject_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        SimpleLockManaged lockManaged1 = new SimpleLockManaged(semaphore);
+        SimpleLockManaged lockManaged2 = new SimpleLockManaged(semaphore);
+
+        Future<?> r1 = executor.submit(lockManaged1::useResource);
+        Future<?> r2 = executor.submit(lockManaged2::useResourceSomeMore);
+
+        try {
+            r1.get();
+            r2.get();
+            throw new AssertionError("Different locks should allow concurrent access to resources");
+        } catch (ExecutionException e) {
+            if (!(e.getCause() instanceof ConcurrentModificationException)) {
+                throw e;
+            }
+            // we expected a concurrent modification exception here
+        }
+
+    }
+
+    @Component
+    public static class AnotherSimpleLockManaged {
+
+        private Semaphore semaphore;
+
+        public AnotherSimpleLockManaged(Semaphore semaphore) {
+            this.semaphore = semaphore;
+        }
+
+        @Lock("my_lock")
+        protected void useResourceAgain() {
+            LOG.info("{} trying to acquire semaphore", this);
+            boolean acquired = semaphore.tryAcquire();
+
+            if (!acquired) {
+                LOG.info("{} failed to acquire semaphore", this);
+                throw new ConcurrentModificationException("Semaphore was acquired concurrently");
+            }
+
+            // hold the permit for a few ms
+            try {
+                LOG.info("{} holding permit for 500ms", this);
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            } finally {
+                LOG.info("{} releasing semaphore", this);
+                semaphore.release();
+            }
+        }
+    }
+
+    @Test
+    public void mutexTest_onDifferentClass_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        SimpleLockManaged lockManaged1 = new SimpleLockManaged(semaphore);
+        AnotherSimpleLockManaged lockManaged2 = new AnotherSimpleLockManaged(semaphore);
+
+        Future<?> r1 = executor.submit(lockManaged1::useResource);
+        Future<?> r2 = executor.submit(lockManaged2::useResourceAgain);
+
+        try {
+            r1.get();
+            r2.get();
+        } catch (ExecutionException e) {
+            if (e.getCause() instanceof ConcurrentModificationException) {
+                throw new AssertionError("Access to shared resource was not mutually exclusive as required", e);
+            } else {
+                throw e;
+            }
+        }
+    }
+
+    /**
+     * This class is annotated with @Lock, but does not have a @Component annotation, so it should not be instrumented.
+     */
+    public static class NotLockManaged {
+
+        public Semaphore semaphore;
+
+        public NotLockManaged(Semaphore semaphore) {
+            this.semaphore = semaphore;
+        }
+
+        @Lock("my_lock_0")
+        public void useResource() {
+            LOG.info("{} trying to acquire semaphore", this);
+            boolean acquired = semaphore.tryAcquire();
+
+            if (!acquired) {
+                LOG.info("{} failed to acquire semaphore", this);
+                throw new ConcurrentModificationException("Semaphore was acquired concurrently");
+            }
+
+            // hold the permit for a few ms
+            try {
+                LOG.info("{} holding permit for 500ms", this);
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            } finally {
+                LOG.info("{} releasing semaphore", this);
+                semaphore.release();
+            }
+        }
+    }
+
+    @Test
+    public void testOnNonComponent_shouldNotBeInstrumented() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        NotLockManaged notManaged = new NotLockManaged(semaphore);
+
+        Future<?> r1 = executor.submit(notManaged::useResource);
+        Future<?> r2 = executor.submit(notManaged::useResource);
+
+        try {
+            r1.get();
+            r2.get();
+            throw new AssertionError("Only classes with the @Component annotation should be instrumented");
+        } catch (ExecutionException e) {
+            if (!(e.getCause() instanceof ConcurrentModificationException)) {
+                throw e;
+            }
+            // we expected a concurrent modification exception here
+        }
+    }
+
+    @Component
+    public static class LockManagedWithParameter {
+
+        @Lock("my_lock_1")
+        protected void useResource(Semaphore semaphore) {
+            LOG.info("{} trying to acquire semaphore", this);
+            boolean acquired = semaphore.tryAcquire();
+
+            if (!acquired) {
+                LOG.info("{} failed to acquire semaphore", this);
+                throw new ConcurrentModificationException("Semaphore was acquired concurrently");
+            }
+
+            // hold the permit for a few ms
+            try {
+                LOG.info("{} holding permit for 500ms", this);
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            } finally {
+                LOG.info("{} releasing semaphore", this);
+                semaphore.release();
+            }
+        }
+    }
+
+    @Test
+    public void mutexTest_withParameter_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        LockManagedWithParameter lockManaged = new LockManagedWithParameter();
+
+        Future<?> r1 = executor.submit(() -> lockManaged.useResource(semaphore));
+        Future<?> r2 = executor.submit(() -> lockManaged.useResource(semaphore));
+
+        try {
+            r1.get();
+            r2.get();
+        } catch (ExecutionException e) {
+            if (e.getCause() instanceof ConcurrentModificationException) {
+                throw new AssertionError("Access to shared resource was not mutually exclusive as required", e);
+            } else {
+                throw e;
+            }
+        }
+    }
+
+
+    @Component
+    public static class LockManagedWithReturnValue {
+
+        public Semaphore semaphore;
+
+        public LockManagedWithReturnValue(Semaphore semaphore) {
+            this.semaphore = semaphore;
+        }
+
+        @Lock("my_lock")
+        public Integer useResource() {
+            useResourceImpl();
+            return 42;
+        }
+
+        private void useResourceImpl() {
+            LOG.info("{} trying to acquire semaphore", this);
+            boolean acquired = semaphore.tryAcquire();
+
+            if (!acquired) {
+                LOG.info("{} failed to acquire semaphore", this);
+                throw new ConcurrentModificationException("Semaphore was acquired concurrently");
+            }
+
+            // hold the permit for a few ms
+            try {
+                LOG.info("{} holding permit for 500ms", this);
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            } finally {
+                LOG.info("{} releasing semaphore", this);
+                semaphore.release();
+            }
+        }
+    }
+
+    @Test
+    public void mutexTest_withReturnValue_behavesCorrectly() throws Exception {
+        Semaphore semaphore = new Semaphore(1);
+
+        LockManagedWithReturnValue lockManaged = new LockManagedWithReturnValue(semaphore);
+
+        Future<Integer> r1 = executor.submit(lockManaged::useResource);
+        Future<Integer> r2 = executor.submit(lockManaged::useResource);
+
+        try {
+            Integer i1 = r1.get();
+            Integer i2 = r2.get();
+
+            Assert.assertEquals(Integer.valueOf(42), i1);
+            Assert.assertEquals(Integer.valueOf(42), i2);
+        } catch (ExecutionException e) {
+            if (e.getCause() instanceof ConcurrentModificationException) {
+                throw new AssertionError("Access to shared resource was not mutually exclusive as required", e);
+            } else {
+                throw e;
+            }
+        }
+    }
+
+
+    @Component
+    public static class LockManagedWithParamAndReturnValue {
+
+        private Integer i = 0;
+
+        @Lock("my_lock_2")
+        public Integer checkAndIncrement(Integer test) throws RuntimeException {
+            System.out.println(Thread.currentThread().getName() + " getting value " + i);
+            int x = i;
+
+            if (i < test) {
+                // this condition will always be true in the tests, just to add some logic
+                try {
+                    Thread.sleep(500);
+                } catch (InterruptedException e) {
+                    throw new RuntimeException(e);
+                }
+                x = x + 1;
+                i = x;
+            }
+
+            return i;
+        }
+
+    }
+
+    /**
+     * This test verifies that the instrumentation also works when the function has input parameters and return values.
+     */
+    @Test
+    public void mutexTest_withParamAndReturnValue_behavesCorrectly() throws Exception {
+        LockManagedWithParamAndReturnValue managed = new LockManagedWithParamAndReturnValue();
+
+        Future<Integer> r1 = executor.submit(() -> managed.checkAndIncrement(10));
+        Future<Integer> r2 = executor.submit(() -> managed.checkAndIncrement(10));
+
+        try {
+            Integer i1 = r1.get();
+            Integer i2 = r2.get();
+
+            Assert.assertNotEquals("Result of concurrent increment is equal, indicating a race condition", i1, i2);
+            if (i1 < i2) {
+                Assert.assertEquals(Integer.valueOf(1), i1);
+                Assert.assertEquals(Integer.valueOf(2), i2);
+            } else {
+                Assert.assertEquals(Integer.valueOf(2), i1);
+                Assert.assertEquals(Integer.valueOf(1), i2);
+            }
+        } catch (ExecutionException e) {
+            if (e.getCause() instanceof ConcurrentModificationException) {
+                throw new AssertionError("Access to shared resource was not mutually exclusive as required", e);
+            } else {
+                throw e;
+            }
+        }
+    }
+
+}

ass2-ioc/src/test/java/dst/ass2/ioc/tests/lock/ThreadPoolResource.java

@@ -0,0 +1,65 @@
+package dst.ass2.ioc.tests.lock;
+
+import org.junit.rules.ExternalResource;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Simple JUnit Rule wrapper of a fixed thread pool {@link ExecutorService} that shuts down after each test execution.
+ */
+public class ThreadPoolResource extends ExternalResource {
+
+    private ExecutorService executor;
+    private int nThreads;
+
+    public ThreadPoolResource(int nThreads) {
+        this.nThreads = nThreads;
+    }
+
+    @Override
+    protected void before() {
+        executor = Executors.newFixedThreadPool(nThreads);
+    }
+
+    @Override
+    protected void after() {
+        shutdownAndAwaitTermination(executor);
+    }
+
+    public Future<?> submit(Runnable task) {
+        return executor.submit(task);
+    }
+
+    public <T> Future<T> submit(Callable<T> task) {
+        return executor.submit(task);
+    }
+
+    public ExecutorService getExecutor() {
+        return executor;
+    }
+
+    private void shutdownAndAwaitTermination(ExecutorService pool) {
+        System.out.println("shutting down pool");
+        pool.shutdown(); // Disable new tasks from being submitted
+        try {
+            // Wait a while for existing tasks to terminate
+            System.out.println("awaiting pool termination");
+            if (!pool.awaitTermination(5, TimeUnit.SECONDS)) {
+                pool.shutdownNow(); // Cancel currently executing tasks
+                // Wait a while for tasks to respond to being cancelled
+                if (!pool.awaitTermination(5, TimeUnit.SECONDS)) {
+                    System.err.println("Pool did not terminate");
+                }
+            }
+        } catch (InterruptedException ie) {
+            // (Re-)Cancel if current thread also interrupted
+            pool.shutdownNow();
+            // Preserve interrupt status
+            Thread.currentThread().interrupt();
+        }
+    }
+}