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From mattf-horton <...@git.apache.org>
Subject [GitHub] metron pull request #530: METRON-777 Metron Extension System and Parser Exte...
Date Fri, 11 Aug 2017 23:50:08 GMT
Github user mattf-horton commented on a diff in the pull request:

    https://github.com/apache/metron/pull/530#discussion_r132796537
  
    --- Diff: bundles-lib/src/main/java/org/apache/metron/bundles/ExtensionManager.java ---
    @@ -0,0 +1,436 @@
    +/*
    + * 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 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.FileUtils;
    +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.*;
    +import java.util.concurrent.ConcurrentHashMap;
    +import java.util.concurrent.atomic.AtomicBoolean;
    +
    +/**
    + * Scans through the classpath to load all extension components using the service provider
API and
    + * running through all classloaders (root, BUNDLEs).
    + *
    + * @ThreadSafe - is immutable
    + */
    +@SuppressWarnings("rawtypes")
    +public class ExtensionManager {
    +
    +  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);
    +
    +  // Maps a service definition (interface) to those classes that implement the interface
    +  private static final Map<Class, Set<Class>> definitionMap = new HashMap<>();
    +
    +  private static final Map<String, List<Bundle>> classNameBundleLookup =
new HashMap<>();
    +  private static final Map<BundleCoordinates, Bundle> bundleCoordinateBundleLookup
= new HashMap<>();
    +  private static final Map<ClassLoader, Bundle> classLoaderBundleLookup = new HashMap<>();
    +
    +  private static final Set<String> requiresInstanceClassLoading = new HashSet<>();
    +  private static final Map<String, ClassLoader> instanceClassloaderLookup = new
ConcurrentHashMap<>();
    +
    +  private static AtomicBoolean inited = new AtomicBoolean(false);
    +
    +  // should initialize class definitions
    +  public static void initClassDefinitions(final List<Class> classes) {
    +    if (classes != null) {
    +      for (Class clazz : classes) {
    +        definitionMap.put(clazz, new HashSet<>());
    +      }
    +    }
    +    inited.set(true);
    +  }
    +
    +  public static void resetClassDefinitions() {
    +    definitionMap.clear();
    +    inited.set(false);
    +  }
    +
    +  /**
    +   * 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 static void discoverExtensions(final Bundle systemBundle, final Set<Bundle>
bundles)
    +      throws NotInitializedException {
    +    checkInitialized();
    +    // get the current context class loader
    +    ClassLoader currentContextClassLoader = Thread.currentThread().getContextClassLoader();
    +
    +    // load the system bundle first so that any extensions found in JARs directly in
lib will be registered as
    +    // being from the system bundle and not from all the other Bundles
    +    loadExtensions(systemBundle);
    +    bundleCoordinateBundleLookup.put(systemBundle.getBundleDetails().getCoordinates(),
systemBundle);
    +
    +    // consider each bundle class loader
    +    for (final Bundle bundle : bundles) {
    +      // Must set the context class loader to the bundle classloader itself
    +      // so that static initialization techniques that depend on the context class loader
will work properly
    +      final ClassLoader ncl = bundle.getClassLoader();
    +      Thread.currentThread().setContextClassLoader(ncl);
    +      loadExtensions(bundle);
    +
    +      // Create a look-up from withCoordinates to bundle
    +      bundleCoordinateBundleLookup.put(bundle.getBundleDetails().getCoordinates(), bundle);
    +    }
    +
    +    // restore the current context class loader if appropriate
    +    if (currentContextClassLoader != null) {
    +      Thread.currentThread().setContextClassLoader(currentContextClassLoader);
    +    }
    +  }
    +
    +  /**
    +   * Returns a bundle representing the system class loader.
    +   *
    +   * @param bundleProperties a BundleProperties instance which will be used to obtain
the default
    +   * Bundle library path, which will become the working directory of the returned bundle
    +   * @return a bundle for the system class loader
    +   */
    +  public static Bundle createSystemBundle(final FileSystemManager fileSystemManager,
    +      final BundleProperties bundleProperties) throws FileSystemException, URISyntaxException
{
    +    final ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
    +
    +    final String bundlesLibraryDirectory = bundleProperties
    +        .getProperty(BundleProperties.BUNDLE_LIBRARY_DIRECTORY);
    +    if (StringUtils.isBlank(bundlesLibraryDirectory)) {
    +      throw new IllegalStateException(
    +          "Unable to create system bundle because " + BundleProperties.BUNDLE_LIBRARY_DIRECTORY
    +              + " was null or empty");
    +    }
    +    final URI bundlesLibraryDirURI = bundleProperties.getBundleLibraryDirectory();
    +    FileObject bundleDir = fileSystemManager.resolveFile(bundlesLibraryDirURI);
    +
    +    // Test if the source Bundles can be read
    +    FileUtils.ensureDirectoryExistAndCanRead(bundleDir);
    +
    +    final BundleDetails systemBundleDetails = new BundleDetails.Builder()
    +        .withBundleFile(bundleDir)
    +        .withCoordinates(SYSTEM_BUNDLE_COORDINATE)
    +        .build();
    +
    +    return new Bundle(systemBundleDetails, systemClassLoader);
    +  }
    +
    +  /**
    +   * Loads extensions from the specified bundle.
    +   *
    +   * @param bundle from which to load extensions
    +   */
    +  @SuppressWarnings("unchecked")
    +  private static void loadExtensions(final Bundle bundle) throws NotInitializedException
{
    +    checkInitialized();
    +    for (final Map.Entry<Class, Set<Class>> entry : definitionMap.entrySet())
{
    +      // this is another extention point
    +      // what we care about here is getting the right classes from the classloader for
the bundle
    +      // this *could* be as a 'service' itself with different implementations
    +      // The NAR system uses the ServiceLoader, but this chokes on abstract classes,
because for some
    +      // reason it feels compelled to instantiate the class,
    +      // which there may be in the system.
    +      // Changed to ClassIndex
    --- End diff --
    
    Use of ClassIndex is the best thing about your adaptation :-)
    Do you have plenty of unit tests for the various cases of multiple bundles in one file,
etc?


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