Github user ottobackwards commented on a diff in the pull request:
https://github.com/apache/metron/pull/530#discussion_r133079542
--- Diff:
bundles-lib/src/main/java/org/apache/metron/bundles/ExtensionManager.java ---
@@ -0,0 +1,540 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.metron.bundles;
+
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import org.apache.commons.vfs2.FileObject;
+import org.apache.commons.vfs2.FileSystemException;
+import org.apache.commons.vfs2.FileSystemManager;
+import org.apache.metron.bundles.bundle.Bundle;
+import org.apache.metron.bundles.bundle.BundleCoordinates;
+import org.apache.metron.bundles.bundle.BundleDetails;
+import org.apache.metron.bundles.util.BundleProperties;
+import org.apache.metron.bundles.util.DummyFileObject;
+import org.apache.metron.bundles.util.FileUtils;
+import org.apache.metron.bundles.util.ImmutableCollectionUtils;
+import org.apache.metron.bundles.util.StringUtils;
+import
org.apache.metron.bundles.annotation.behavior.RequiresInstanceClassLoading;
+
+import org.atteo.classindex.ClassIndex;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.lang.reflect.Modifier;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * A Singleton class for scanning through the classpath to load all
extension components using
+ * the ClassIndex and running through all classloaders (root, BUNDLEs).
+ *
+ *
+ * @ThreadSafe - is immutable
+ */
+@SuppressWarnings("rawtypes")
+public class ExtensionManager {
+
+ private static volatile ExtensionManager extensionManager;
+ private volatile InitContext initContext;
+
+ private static final Logger logger =
LoggerFactory.getLogger(ExtensionManager.class);
+
+ public static final BundleCoordinates SYSTEM_BUNDLE_COORDINATE = new
BundleCoordinates(
+ BundleCoordinates.DEFAULT_GROUP, "system",
BundleCoordinates.DEFAULT_VERSION);
+
+ private static final class InitContext {
+
+ // Maps a service definition (interface) to those classes that
implement the interface
+ private final Map<Class, Set<Class>> definitionMap;
+ private final Map<String, List<Bundle>> classNameBundleLookup;
+ private final Map<BundleCoordinates, Bundle>
bundleCoordinateBundleLookup;
+ private final Map<ClassLoader, Bundle> classLoaderBundleLookup;
+ private final Set<String> requiresInstanceClassLoading;
+ private final Map<String, ClassLoader> instanceClassloaderLookup;
+
+ private InitContext(Map<Class, Set<Class>> definitionMap,
+ Map<String, List<Bundle>> classNameBundleLookup,
+ Map<BundleCoordinates, Bundle> bundleCoordinateBundleLookup,
+ Map<ClassLoader, Bundle> classLoaderBundleLookup,
+ Set<String> requiresInstanceClassLoading,
+ Map<String, ClassLoader> instanceClassloaderLookup) {
+
+ this.definitionMap =
ImmutableCollectionUtils.immutableMapOfSets(definitionMap);
+ this.classNameBundleLookup = ImmutableCollectionUtils
+ .immutableMapOfLists(classNameBundleLookup);
+ this.bundleCoordinateBundleLookup =
ImmutableMap.copyOf(bundleCoordinateBundleLookup);
+ this.classLoaderBundleLookup =
ImmutableMap.copyOf(classLoaderBundleLookup);
+ this.requiresInstanceClassLoading =
ImmutableSet.copyOf(requiresInstanceClassLoading);
+ this.instanceClassloaderLookup = new
ConcurrentHashMap<>(instanceClassloaderLookup);
+ }
+ }
+
+ private ExtensionManager(){}
+
+ /**
+ * @return The singleton instance of the ExtensionManager
+ */
+ public static ExtensionManager getInstance() {
+ ExtensionManager result = extensionManager;
+ if (result == null) {
+ synchronized (ExtensionManager.class) {
+ result = extensionManager;
+ if (result == null) {
+ extensionManager = new ExtensionManager();
+ result = extensionManager;
+ }
+ }
+ }
+ return result;
+ }
+
+ /**
+ * Uninitializes the ExtensionManager.
+ * TESTING ONLY
+ */
+ public static void reset() {
+ synchronized (ExtensionManager.class) {
+ getInstance().forgetExtensions();
+ extensionManager = null;
+ }
+ }
+
+ private void forgetExtensions() {
+ initContext = null;
+ }
+
+
+ /**
+ * Loads all extension class types that can be found on the bootstrap
classloader and by creating
+ * classloaders for all BUNDLES found within the classpath.
+ *
+ * @param bundles the bundles to scan through in search of extensions
+ */
+ public void init(final List<Class> classes, final Bundle systemBundle,
final Set<Bundle> bundles)
+ throws NotInitializedException {
+
+ InitContext ic = initContext;
+ if (ic == null) {
+ synchronized (this) {
--- End diff --
done
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