Decoupled the DataMiningServerImpl from the BundleContext

This allowed me to write a test for the function registry update
mechanism.

java/com.sap.sailing.datamining/src/com/sap/sailing/datamining/Activator.java

@@ -5,7 +5,7 @@ import org.osgi.framework.BundleContext;
 import org.osgi.framework.ServiceRegistration;
 
 import com.sap.sailing.datamining.impl.data.SailingDataMiningClassesWithFunctionsService;
-import com.sap.sse.datamining.functions.ClassesWithFunctionsService;
+import com.sap.sse.datamining.ClassesWithFunctionsService;
 
 public class Activator implements BundleActivator {
     

java/com.sap.sailing.datamining/src/com/sap/sailing/datamining/impl/data/SailingDataMiningClassesWithFunctionsService.java

@@ -4,7 +4,7 @@ import java.util.HashSet;
 import java.util.Set;
 
 import com.sap.sailing.datamining.data.HasGPSFixContext;
-import com.sap.sse.datamining.functions.ClassesWithFunctionsService;
+import com.sap.sse.datamining.ClassesWithFunctionsService;
 
 public class SailingDataMiningClassesWithFunctionsService implements ClassesWithFunctionsService {
 

java/com.sap.sse.datamining.test/src/com/sap/sse/datamining/impl/TestDataMiningServer.java

@@ -0,0 +1,90 @@
+package com.sap.sse.datamining.impl;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import com.sap.sse.datamining.ClassesWithFunctionsProvider;
+import com.sap.sse.datamining.DataMiningServer;
+import com.sap.sse.datamining.functions.Function;
+import com.sap.sse.datamining.functions.FunctionProvider;
+import com.sap.sse.datamining.functions.FunctionRegistry;
+import com.sap.sse.datamining.impl.functions.RegistryFunctionProvider;
+import com.sap.sse.datamining.impl.functions.SimpleFunctionRegistry;
+import com.sap.sse.datamining.test.functions.registry.test_contexts.Test_HasLegContext;
+import com.sap.sse.datamining.test.functions.registry.test_contexts.Test_HasRaceContext;
+import com.sap.sse.datamining.test.util.ExpectedFunctionRegistryUtil;
+
+public class TestDataMiningServer {
+    
+    private static ExpectedFunctionRegistryUtil expectedFunctionRegistryUtil;
+
+    @BeforeClass
+    public static void intializeExpectedFunctions() throws NoSuchMethodException, SecurityException {
+        expectedFunctionRegistryUtil = new ExpectedFunctionRegistryUtil();
+    }
+
+    @Test
+    public void testThatTheFunctionRegistryIsAllwaysUpToDate() {
+        FunctionRegistry registry = new SimpleFunctionRegistry();
+        FunctionProvider provider = new RegistryFunctionProvider(registry);
+        OpenClassesWithFunctionsProvider classesWithFunctionsProvider = new OpenClassesWithFunctionsProvider();
+        DataMiningServer server = new DataMiningServerImpl(registry, provider, classesWithFunctionsProvider);
+        
+        assertThat("The function registry should be empty.",
+                   server.getFunctionRegistry().getAllFunctions().isEmpty(),
+                   is(true));
+        
+        classesWithFunctionsProvider.internalClassesWithMarkedMethods.add(Test_HasLegContext.class);
+        Collection<Function<?>> expectedFunctions = new HashSet<>();
+        expectedFunctions.addAll(expectedFunctionRegistryUtil.getExpectedFunctionsFor(Test_HasLegContext.class));
+        expectedFunctions.addAll(expectedFunctionRegistryUtil.getExpectedFunctionsFor(Test_HasRaceContext.class));
+        assertThat(server.getFunctionRegistry().getAllFunctions(), is(expectedFunctions));
+        
+        classesWithFunctionsProvider.internalClassesWithMarkedMethods.remove(Test_HasLegContext.class);
+        classesWithFunctionsProvider.internalClassesWithMarkedMethods.add(Test_HasRaceContext.class);
+        expectedFunctions = expectedFunctionRegistryUtil.getExpectedFunctionsFor(Test_HasRaceContext.class);
+        assertThat(server.getFunctionRegistry().getAllFunctions(), is(expectedFunctions));
+    }
+    
+    @Test
+    public void testThatTheRegistryUpdateWorksWithNullCollections() {
+        FunctionRegistry registry = new SimpleFunctionRegistry();
+        FunctionProvider provider = new RegistryFunctionProvider(registry);
+        OpenClassesWithFunctionsProvider classesWithFunctionsProvider = new OpenClassesWithFunctionsProvider();
+        DataMiningServer server = new DataMiningServerImpl(registry, provider, classesWithFunctionsProvider);
+        
+        classesWithFunctionsProvider.internalClassesWithMarkedMethods = null;
+        classesWithFunctionsProvider.externalLibraryClasses = null;
+        server.getFunctionRegistry();
+    }
+
+    private class OpenClassesWithFunctionsProvider implements ClassesWithFunctionsProvider {
+
+        public Set<Class<?>> internalClassesWithMarkedMethods;
+        public Set<Class<?>> externalLibraryClasses;
+        
+        public OpenClassesWithFunctionsProvider() {
+            internalClassesWithMarkedMethods = new HashSet<>();
+            externalLibraryClasses = new HashSet<>();
+        }
+
+        @Override
+        public Set<Class<?>> getInternalClassesWithMarkedMethods() {
+            return internalClassesWithMarkedMethods;
+        }
+
+        @Override
+        public Set<Class<?>> getExternalLibraryClasses() {
+            return externalLibraryClasses;
+        }
+        
+    }
+    
+}

java/com.sap.sse.datamining.test/src/com/sap/sse/datamining/impl/functions/TestSimpleFunctionRegistry.java

@@ -21,14 +21,14 @@ import com.sap.sse.datamining.test.util.ExpectedFunctionRegistryUtil;
 
 public class TestSimpleFunctionRegistry {
     
-    private static ExpectedFunctionRegistryUtil functionRegistryUtil;
+    private static ExpectedFunctionRegistryUtil expectedFunctionRegistryUtil;
     
     private Set<Class<?>> internalClassesToScan;
     private HashSet<Class<?>> externalClassesToScan;
 
     @BeforeClass
     public static void intializeExpectedFunctions() throws NoSuchMethodException, SecurityException {
-        functionRegistryUtil = new ExpectedFunctionRegistryUtil();
+        expectedFunctionRegistryUtil = new ExpectedFunctionRegistryUtil();
     }
     
     @Before
@@ -48,14 +48,14 @@ public class TestSimpleFunctionRegistry {
         registry.registerAllWithExternalFunctionPolicy(externalClassesToScan);
         
         Collection<Function<?>> expectedDimensions = new HashSet<>();
-        expectedDimensions.addAll(functionRegistryUtil.getExpectedDimensionsFor(Test_HasLegContext.class));
+        expectedDimensions.addAll(expectedFunctionRegistryUtil.getExpectedDimensionsFor(Test_HasLegContext.class));
-        expectedDimensions.addAll(functionRegistryUtil.getExpectedDimensionsFor(Test_HasRaceContext.class));
+        expectedDimensions.addAll(expectedFunctionRegistryUtil.getExpectedDimensionsFor(Test_HasRaceContext.class));
         assertThat(registry.getDimensions(), is(expectedDimensions));
         
-        Collection<Function<?>> expectedStatistics = functionRegistryUtil.getExpectedStatisticsFor(Test_HasLegContext.class);
+        Collection<Function<?>> expectedStatistics = expectedFunctionRegistryUtil.getExpectedStatisticsFor(Test_HasLegContext.class);
         assertThat(registry.getStatistics(), is(expectedStatistics));
         
-        Collection<Function<?>> expectedExternalFunctions = functionRegistryUtil.getExpectedExternalFunctionsFor(Test_ExternalLibraryClass.class);
+        Collection<Function<?>> expectedExternalFunctions = expectedFunctionRegistryUtil.getExpectedExternalFunctionsFor(Test_ExternalLibraryClass.class);
         assertThat(registry.getExternalFunctions(), is(expectedExternalFunctions));
     }
     
@@ -65,15 +65,15 @@ public class TestSimpleFunctionRegistry {
         registry.registerAllWithInternalFunctionPolicy(internalClassesToScan);
         
         Collection<Function<?>> expectedDimensions = new HashSet<>();
-        expectedDimensions.addAll(functionRegistryUtil.getExpectedDimensionsFor(Test_HasLegContext.class));
+        expectedDimensions.addAll(expectedFunctionRegistryUtil.getExpectedDimensionsFor(Test_HasLegContext.class));
-        expectedDimensions.addAll(functionRegistryUtil.getExpectedDimensionsFor(Test_HasRaceContext.class));
+        expectedDimensions.addAll(expectedFunctionRegistryUtil.getExpectedDimensionsFor(Test_HasRaceContext.class));
         assertThat(registry.getDimensions(), is(expectedDimensions));
         
         Set<Class<?>> classesToUnregister = new HashSet<>();
         classesToUnregister.add(Test_HasLegContext.class);
         registry.unregisterAllFunctionsOf(classesToUnregister);
         
-        expectedDimensions = functionRegistryUtil.getExpectedDimensionsFor(Test_HasRaceContext.class);
+        expectedDimensions = expectedFunctionRegistryUtil.getExpectedDimensionsFor(Test_HasRaceContext.class);
         assertThat(registry.getDimensions(), is(expectedDimensions));
 
         registry.registerAllWithInternalFunctionPolicy(internalClassesToScan);
@@ -81,7 +81,7 @@ public class TestSimpleFunctionRegistry {
         classesToUnregister.add(Test_HasRaceContext.class);
         registry.unregisterAllFunctionsOf(classesToUnregister);
         
-        expectedDimensions = functionRegistryUtil.getExpectedDimensionsFor(Test_HasLegContext.class);
+        expectedDimensions = expectedFunctionRegistryUtil.getExpectedDimensionsFor(Test_HasLegContext.class);
         assertThat(registry.getDimensions(), is(expectedDimensions));
     }
 

java/com.sap.sse.datamining.test/src/com/sap/sse/datamining/test/util/ExpectedFunctionRegistryUtil.java

@@ -1,10 +1,12 @@
 package com.sap.sse.datamining.test.util;
 
 import java.lang.reflect.Method;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Set;
 
 import com.sap.sse.datamining.factories.FunctionFactory;
 import com.sap.sse.datamining.functions.Function;
@@ -111,15 +113,26 @@ public class ExpectedFunctionRegistryUtil {
     }
     
     public Collection<Function<?>> getExpectedDimensionsFor(Class<?> declaringType) {
-        return expectedDimensions.get(declaringType);
+        Collection<Function<?>> expectedDimensions = this.expectedDimensions.get(declaringType);
+        return expectedDimensions != null ? expectedDimensions : new ArrayList<Function<?>>();
     }
     
     public Collection<Function<?>> getExpectedStatisticsFor(Class<?> declaringType) {
-        return expectedStatistics.get(declaringType);
+        Collection<Function<?>> expectedStatistics = this.expectedStatistics.get(declaringType);
+        return expectedStatistics != null ? expectedStatistics : new ArrayList<Function<?>>();
     }
     
     public Collection<Function<?>> getExpectedExternalFunctionsFor(Class<?> declaringType) {
-        return expectedExternalFunctions.get(declaringType);
+        Collection<Function<?>> expectedExternalFunctions = this.expectedExternalFunctions.get(declaringType);
+        return expectedExternalFunctions != null ? expectedExternalFunctions : new ArrayList<Function<?>>();
+    }
+
+    public Set<Function<?>> getExpectedFunctionsFor(Class<?> declaringType) {
+        Set<Function<?>> expectedFunctions = new HashSet<>();
+        expectedFunctions.addAll(getExpectedDimensionsFor(declaringType));
+        expectedFunctions.addAll(getExpectedStatisticsFor(declaringType));
+        expectedFunctions.addAll(getExpectedExternalFunctionsFor(declaringType));
+        return expectedFunctions;
     }
 
 }

java/com.sap.sse.datamining/src/com/sap/sse/datamining/ClassesWithFunctionsProvider.java

@@ -0,0 +1,10 @@
+package com.sap.sse.datamining;
+
+import java.util.Set;
+
+public interface ClassesWithFunctionsProvider {
+
+    public Set<Class<?>> getInternalClassesWithMarkedMethods();
+    public Set<Class<?>> getExternalLibraryClasses();
+
+}

java/com.sap.sse.datamining/src/com/sap/sse/datamining/ClassesWithFunctionsService.java

@@ -1,4 +1,4 @@
-package com.sap.sse.datamining.functions;
+package com.sap.sse.datamining;
 
 import java.util.Set;
 

java/com.sap.sse.datamining/src/com/sap/sse/datamining/impl/DataMiningActivator.java

@@ -1,12 +1,22 @@
 package com.sap.sse.datamining.impl;
 
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 import org.osgi.framework.BundleActivator;
 import org.osgi.framework.BundleContext;
+import org.osgi.framework.InvalidSyntaxException;
+import org.osgi.framework.ServiceReference;
 
+import com.sap.sse.datamining.ClassesWithFunctionsProvider;
+import com.sap.sse.datamining.ClassesWithFunctionsService;
 import com.sap.sse.datamining.DataMiningServer;
 import com.sap.sse.datamining.functions.FunctionProvider;
 import com.sap.sse.datamining.functions.FunctionRegistry;
@@ -14,9 +24,9 @@ import com.sap.sse.datamining.i18n.DataMiningStringMessages;
 import com.sap.sse.datamining.impl.functions.RegistryFunctionProvider;
 import com.sap.sse.datamining.impl.functions.SimpleFunctionRegistry;
 
-public class DataMiningActivator implements BundleActivator {
+public class DataMiningActivator implements BundleActivator, ClassesWithFunctionsProvider {
 
-//    private static final Logger LOGGER = Logger.getLogger(DataMiningActivator.class.getName());
+    private static final Logger LOGGER = Logger.getLogger(DataMiningActivator.class.getName());
     private static final int THREAD_POOL_SIZE = Math.max(Runtime.getRuntime().availableProcessors(), 3);
 
     private static BundleContext context;
@@ -34,7 +44,7 @@ public class DataMiningActivator implements BundleActivator {
 
         FunctionRegistry functionRegistry = new SimpleFunctionRegistry();
         FunctionProvider functionProvider = new RegistryFunctionProvider(functionRegistry);
-        dataMiningServer = new DataMiningServerImpl(functionRegistry, functionProvider);
+        dataMiningServer = new DataMiningServerImpl(functionRegistry, functionProvider, this);
         registerDataMiningServer();
     }
 
@@ -58,4 +68,63 @@ public class DataMiningActivator implements BundleActivator {
         return context;
     }
 
+    @Override
+    public Set<Class<?>> getInternalClassesWithMarkedMethods() {
+        Set<Class<?>> internalClassesWithMarkedMethods = new HashSet<>();
+        
+        for (ServiceReference<ClassesWithFunctionsService> serviceReference : getAllClassesWithMarkedMethodsServices()) {
+            internalClassesWithMarkedMethods.addAll(getInternalClassesWithMarkedMethodsFromService(serviceReference));
+        }
+        return internalClassesWithMarkedMethods;
+    }
+
+    @Override
+    public Set<Class<?>> getExternalLibraryClasses() {
+        Set<Class<?>> externalLibraryClasses = new HashSet<>();
+        
+        for (ServiceReference<ClassesWithFunctionsService> serviceReference : getAllClassesWithMarkedMethodsServices()) {
+            externalLibraryClasses.addAll(getExternalLibraryClassesFromService(serviceReference));
+        }
+        return externalLibraryClasses;
+    }
+
+    private Collection<ServiceReference<ClassesWithFunctionsService>> getAllClassesWithMarkedMethodsServices() {
+        try {
+            ServiceReference<?>[] serviceReferences = context.getServiceReferences(ClassesWithFunctionsService.class.getName(), null);
+            if (serviceReferences != null) {
+                return castServiceReferences(serviceReferences);
+            }
+        } catch (InvalidSyntaxException e) {
+            LOGGER.log(Level.SEVERE, "Error getting the service references. Data mining won't work.", e);
+        }
+        LOGGER.log(Level.SEVERE, "There were no " + ClassesWithFunctionsService.class.getName() + "-Services registered. Data mining won't work.");
+        return new ArrayList<>();
+    }
+
+    private Collection<ServiceReference<ClassesWithFunctionsService>> castServiceReferences(ServiceReference<?>[] serviceReferences) {
+        Collection<ServiceReference<ClassesWithFunctionsService>> specificServiceReferences = new ArrayList<>();
+        for (ServiceReference<?> serviceReference : serviceReferences) {
+            try {
+                @SuppressWarnings("unchecked") // This is necessary, because you can't use instanceof with specific generics
+                ServiceReference<ClassesWithFunctionsService> specificServiceReference = (ServiceReference<ClassesWithFunctionsService>) serviceReference;
+                specificServiceReferences.add(specificServiceReference);
+            } catch (ClassCastException exception) {
+                String serviceName = context.getService(serviceReference).getClass().getName();
+                LOGGER.log(Level.WARNING, "Couldn't register the service '" + serviceName + "' to the function registry."
+                        + " Data mining functionalities will be restricted.", exception);
+            }
+        }
+        return specificServiceReferences;
+    }
+
+    private Collection<Class<?>> getInternalClassesWithMarkedMethodsFromService(ServiceReference<ClassesWithFunctionsService> serviceReference) {
+        Collection<Class<?>> internalClassesWithMarkedMethods = context.getService(serviceReference).getInternalClassesWithMarkedMethods();
+        return internalClassesWithMarkedMethods != null ? internalClassesWithMarkedMethods : new ArrayList<Class<?>>();
+    }
+    
+    private Collection<Class<?>> getExternalLibraryClassesFromService(ServiceReference<ClassesWithFunctionsService> serviceReference) {
+        Collection<Class<?>> externalLibraryClasses = context.getService(serviceReference).getExternalLibraryClasses();
+        return externalLibraryClasses != null ? externalLibraryClasses : new ArrayList<Class<?>>();
+    }
+
 }

java/com.sap.sse.datamining/src/com/sap/sse/datamining/impl/DataMiningServerImpl.java

@@ -4,34 +4,28 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.Set;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-import org.osgi.framework.BundleContext;
-import org.osgi.framework.InvalidSyntaxException;
-import org.osgi.framework.ServiceReference;
 
+import com.sap.sse.datamining.ClassesWithFunctionsProvider;
 import com.sap.sse.datamining.DataMiningServer;
-import com.sap.sse.datamining.functions.ClassesWithFunctionsService;
 import com.sap.sse.datamining.functions.FunctionProvider;
 import com.sap.sse.datamining.functions.FunctionRegistry;
 
 public class DataMiningServerImpl implements DataMiningServer {
     
-    private static final Logger LOGGER = Logger.getLogger(DataMiningServerImpl.class.getSimpleName());
+    private final Set<Class<?>> registeredInternalClassesWithMarkedMethods;
-
+    private final Set<Class<?>> registeredExternalLibraryClasses;
-    private final BundleContext context;
-    private final Set<ServiceReference<ClassesWithFunctionsService>> registeredServices;
     
     private final FunctionRegistry functionRegistry;
     private final FunctionProvider functionProvider;
+    private ClassesWithFunctionsProvider classesWithFunctionsProvider;
 
-    public DataMiningServerImpl(FunctionRegistry functionRegistry, FunctionProvider functionProvider) {
+    public DataMiningServerImpl(FunctionRegistry functionRegistry, FunctionProvider functionProvider, ClassesWithFunctionsProvider classesWithFunctionsProvider) {
-        context = DataMiningActivator.getContext();
+        registeredInternalClassesWithMarkedMethods = new HashSet<>();
-        registeredServices = new HashSet<>();
+        registeredExternalLibraryClasses = new HashSet<>();
         
         this.functionRegistry = functionRegistry;
         this.functionProvider = functionProvider;
+        this.classesWithFunctionsProvider = classesWithFunctionsProvider;
         
         updateRegistryIfNecessary();
     }
@@ -49,97 +43,39 @@ public class DataMiningServerImpl implements DataMiningServer {
     }
 
     private void updateRegistryIfNecessary() {
-        Collection<ServiceReference<ClassesWithFunctionsService>> availableServices = getAllClassesWithMarkedMethodsServices();
+        Collection<Class<?>> availableInternalClassesWithMarkedMethods = classesWithFunctionsProvider.getInternalClassesWithMarkedMethods();
-        Collection<ServiceReference<ClassesWithFunctionsService>> servicesToRegister = calculateServicesToRegister(availableServices);
+        Collection<Class<?>> internalClassesWithMarkedMethodsToRegister = getMissingElements(/*from*/ availableInternalClassesWithMarkedMethods, /*in*/ registeredInternalClassesWithMarkedMethods);
-        Collection<ServiceReference<ClassesWithFunctionsService>> servicesToUnregister = calculateServicesToUnregister(availableServices);
+        Collection<Class<?>> internalClassesWithMarkedMethodsToUnregister = getMissingElements(/*from*/ registeredInternalClassesWithMarkedMethods, /*in*/ availableInternalClassesWithMarkedMethods);
         
-        registerServices(servicesToRegister);
+        functionRegistry.unregisterAllFunctionsOf(internalClassesWithMarkedMethodsToUnregister);
-        unregisterServices(servicesToUnregister);
+        registeredInternalClassesWithMarkedMethods.removeAll(internalClassesWithMarkedMethodsToUnregister);
+        functionRegistry.registerAllWithInternalFunctionPolicy(internalClassesWithMarkedMethodsToRegister);
+        registeredInternalClassesWithMarkedMethods.addAll(internalClassesWithMarkedMethodsToRegister);
+
+        Collection<Class<?>> availableExternalLibraryClasses = classesWithFunctionsProvider.getExternalLibraryClasses();
+        Collection<Class<?>> externalLibraryClassesToRegister = getMissingElements(/*from*/ availableExternalLibraryClasses, /*in*/ registeredExternalLibraryClasses);
+        Collection<Class<?>> externalLibraryClassesToUnregister = getMissingElements(/*from*/ registeredExternalLibraryClasses, /*in*/ availableExternalLibraryClasses);
+        
+        functionRegistry.unregisterAllFunctionsOf(externalLibraryClassesToUnregister);
+        registeredExternalLibraryClasses.retainAll(externalLibraryClassesToUnregister);
+        functionRegistry.registerAllWithExternalFunctionPolicy(externalLibraryClassesToRegister);
+        registeredExternalLibraryClasses.addAll(externalLibraryClassesToRegister);
     }
 
-    private Collection<ServiceReference<ClassesWithFunctionsService>> calculateServicesToRegister(
+    private Collection<Class<?>> getMissingElements(Collection<Class<?>> from, Collection<Class<?>> in) {
-            Collection<ServiceReference<ClassesWithFunctionsService>> availableServices) {
+        if (from == null) {
-        Collection<ServiceReference<ClassesWithFunctionsService>> servicesToRegister = new ArrayList<>();
-        
-        for (ServiceReference<ClassesWithFunctionsService> availableService : availableServices) {
-            if (!registeredServices.contains(availableService)) {
-                servicesToRegister.add(availableService);
-            }
-        }
-        
-        return servicesToRegister;
-    }
-
-    private Collection<ServiceReference<ClassesWithFunctionsService>> calculateServicesToUnregister(
-            Collection<ServiceReference<ClassesWithFunctionsService>> availableServices) {
-        Collection<ServiceReference<ClassesWithFunctionsService>> servicesToUnregister = new ArrayList<>();
-        for (ServiceReference<ClassesWithFunctionsService> registeredService : registeredServices) {
-            if (!availableServices.contains(registeredService)) {
-                servicesToUnregister.add(registeredService);
-            }
-        }
-        return servicesToUnregister;
-    }
-
-    private void registerServices(Collection<ServiceReference<ClassesWithFunctionsService>> servicesToRegister) {
-        Set<Class<?>> internalClassesWithMarkedMethods = new HashSet<>();
-        Set<Class<?>> externalLibraryClasses = new HashSet<>();
-        for (ServiceReference<ClassesWithFunctionsService> serviceReference : servicesToRegister) {
-            internalClassesWithMarkedMethods.addAll(getInternalClassesWithMarkedMethodsFromService(serviceReference));
-            externalLibraryClasses.addAll(getExternalLibraryClassesFromService(serviceReference));
-        }
-        
-        functionRegistry.registerAllWithInternalFunctionPolicy(internalClassesWithMarkedMethods);
-        functionRegistry.registerAllWithExternalFunctionPolicy(externalLibraryClasses);
-    }
-
-    private void unregisterServices(Collection<ServiceReference<ClassesWithFunctionsService>> servicesToUnregister) {
-        Set<Class<?>> classesToUnregister = new HashSet<>();
-        for (ServiceReference<ClassesWithFunctionsService> serviceReference : servicesToUnregister) {
-            classesToUnregister.addAll(getInternalClassesWithMarkedMethodsFromService(serviceReference));
-            classesToUnregister.addAll(getExternalLibraryClassesFromService(serviceReference));
-        }
-        
-        functionRegistry.unregisterAllFunctionsOf(classesToUnregister);
-    }
-    
-    private Collection<Class<?>> getInternalClassesWithMarkedMethodsFromService(ServiceReference<ClassesWithFunctionsService> serviceReference) {
-        Collection<Class<?>> internalClassesWithMarkedMethods = context.getService(serviceReference).getInternalClassesWithMarkedMethods();
-        return internalClassesWithMarkedMethods != null ? internalClassesWithMarkedMethods : new ArrayList<Class<?>>();
-    }
-    
-    private Collection<Class<?>> getExternalLibraryClassesFromService(ServiceReference<ClassesWithFunctionsService> serviceReference) {
-        Collection<Class<?>> externalLibraryClasses = context.getService(serviceReference).getExternalLibraryClasses();
-        return externalLibraryClasses != null ? externalLibraryClasses : new ArrayList<Class<?>>();
-    }
-
-    private Collection<ServiceReference<ClassesWithFunctionsService>> getAllClassesWithMarkedMethodsServices() {
-        try {
-            ServiceReference<?>[] serviceReferences = context.getServiceReferences(ClassesWithFunctionsService.class.getName(), null);
-            if (serviceReferences != null) {
-                return castServiceReferences(serviceReferences);
-            }
-        } catch (InvalidSyntaxException e) {
-            LOGGER.log(Level.SEVERE, "Error getting the service references. Data mining won't work.", e);
-        }
-        LOGGER.log(Level.SEVERE, "There were no " + ClassesWithFunctionsService.class.getName() + "-Services registered. Data mining won't work.");
             return new ArrayList<>();
         }
         
-    private Collection<ServiceReference<ClassesWithFunctionsService>> castServiceReferences(ServiceReference<?>[] serviceReferences) {
+        Collection<Class<?>> missingElements = new HashSet<>();
-        Collection<ServiceReference<ClassesWithFunctionsService>> specificServiceReferences = new ArrayList<>();
+        
-        for (ServiceReference<?> serviceReference : serviceReferences) {
+        for (Class<?> element : from) {
-            try {
+            if (!in.contains(element)) {
-                @SuppressWarnings("unchecked") // This is necessary, because you can't use instanceof with specific generics
+                missingElements.add(element);
-                ServiceReference<ClassesWithFunctionsService> specificServiceReference = (ServiceReference<ClassesWithFunctionsService>) serviceReference;
-                specificServiceReferences.add(specificServiceReference);
-            } catch (ClassCastException exception) {
-                String serviceName = context.getService(serviceReference).getClass().getName();
-                LOGGER.log(Level.WARNING, "Couldn't register the service '" + serviceName + "' to the function registry."
-                        + " Data mining functionalities will be restricted.", exception);
             }
         }
-        return specificServiceReferences;
+        
+        return missingElements;
     }
     
 }