Github user mattf-horton commented on a diff in the pull request:
https://github.com/apache/metron/pull/530#discussion_r131815714
--- Diff:
bundles-lib/src/main/java/org/apache/metron/bundles/BundleClassLoaders.java ---
@@ -0,0 +1,353 @@
+/*
+ * 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 java.net.URISyntaxException;
+import java.util.*;
+
+import org.apache.commons.collections.CollectionUtils;
+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.BundleCoordinate;
+import org.apache.metron.bundles.bundle.BundleDetails;
+import org.apache.metron.bundles.util.BundleProperties;
+import org.apache.metron.bundles.util.BundleSelector;
+import org.apache.metron.bundles.util.FileUtils;
+import org.apache.metron.bundles.util.BundleUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A singleton class used to initialize the extension and framework
classloaders.
+ */
+public final class BundleClassLoaders {
+
+ private static volatile BundleClassLoaders bundleClassLoaders;
+ private volatile InitContext initContext;
+ private static final Logger logger =
LoggerFactory.getLogger(BundleClassLoaders.class);
+
+ private final static class InitContext {
+
+ private final List<FileObject> extensionDirs;
+ private final Map<String, Bundle> bundles;
+
+ private InitContext(
+ final List<FileObject> extensionDirs,
+ final Map<String, Bundle> bundles) {
+ this.extensionDirs = extensionDirs;
+ this.bundles = bundles;
+ }
+ }
+
+ private BundleClassLoaders() {
+ }
+
+ /**
+ * @return The singleton instance of the BundleClassLoaders
+ */
+ public static BundleClassLoaders getInstance() {
+ BundleClassLoaders result = bundleClassLoaders;
+ if (result == null) {
+ synchronized (BundleClassLoaders.class) {
+ result = bundleClassLoaders;
+ if (result == null) {
+ bundleClassLoaders = result = new BundleClassLoaders();
--- End diff --
While this construct is legal, it is stylistically deprecated. (The Sun
standards said not to; the Google one is silent about it.) Please make it two
ordinary assignment statements.
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