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[FLINK-11952][1/3] Make ChildFirstClassLoader a top-level class in fl…
…ink-core
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flink-core/src/main/java/org/apache/flink/util/ChildFirstClassLoader.java
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| /* | ||
| * 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. | ||
| */ | ||
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| package org.apache.flink.util; | ||
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| import java.io.IOException; | ||
| import java.net.URL; | ||
| import java.net.URLClassLoader; | ||
| import java.util.ArrayList; | ||
| import java.util.Enumeration; | ||
| import java.util.Iterator; | ||
| import java.util.List; | ||
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| /** | ||
| * A variant of the URLClassLoader that first loads from the URLs and only after that from the parent. | ||
| * | ||
| * <p>{@link #getResourceAsStream(String)} uses {@link #getResource(String)} internally so we | ||
| * don't override that. | ||
| */ | ||
| public final class ChildFirstClassLoader extends URLClassLoader { | ||
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| /** | ||
| * The classes that should always go through the parent ClassLoader. This is relevant | ||
| * for Flink classes, for example, to avoid loading Flink classes that cross the | ||
| * user-code/system-code barrier in the user-code ClassLoader. | ||
| */ | ||
| private final String[] alwaysParentFirstPatterns; | ||
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| public ChildFirstClassLoader(URL[] urls, ClassLoader parent, String[] alwaysParentFirstPatterns) { | ||
| super(urls, parent); | ||
| this.alwaysParentFirstPatterns = alwaysParentFirstPatterns; | ||
| } | ||
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| @Override | ||
| protected synchronized Class<?> loadClass( | ||
| String name, boolean resolve) throws ClassNotFoundException { | ||
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| // First, check if the class has already been loaded | ||
| Class<?> c = findLoadedClass(name); | ||
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| if (c == null) { | ||
| // check whether the class should go parent-first | ||
| for (String alwaysParentFirstPattern : alwaysParentFirstPatterns) { | ||
| if (name.startsWith(alwaysParentFirstPattern)) { | ||
| return super.loadClass(name, resolve); | ||
| } | ||
| } | ||
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| try { | ||
| // check the URLs | ||
| c = findClass(name); | ||
| } catch (ClassNotFoundException e) { | ||
| // let URLClassLoader do it, which will eventually call the parent | ||
| c = super.loadClass(name, resolve); | ||
| } | ||
| } | ||
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| if (resolve) { | ||
| resolveClass(c); | ||
| } | ||
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| return c; | ||
| } | ||
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| @Override | ||
| public URL getResource(String name) { | ||
| // first, try and find it via the URLClassloader | ||
| URL urlClassLoaderResource = findResource(name); | ||
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| if (urlClassLoaderResource != null) { | ||
| return urlClassLoaderResource; | ||
| } | ||
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| // delegate to super | ||
| return super.getResource(name); | ||
| } | ||
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| @Override | ||
| public Enumeration<URL> getResources(String name) throws IOException { | ||
| // first get resources from URLClassloader | ||
| Enumeration<URL> urlClassLoaderResources = findResources(name); | ||
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| final List<URL> result = new ArrayList<>(); | ||
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| while (urlClassLoaderResources.hasMoreElements()) { | ||
| result.add(urlClassLoaderResources.nextElement()); | ||
| } | ||
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| // get parent urls | ||
| Enumeration<URL> parentResources = getParent().getResources(name); | ||
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| while (parentResources.hasMoreElements()) { | ||
| result.add(parentResources.nextElement()); | ||
| } | ||
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| return new Enumeration<URL>() { | ||
| Iterator<URL> iter = result.iterator(); | ||
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| public boolean hasMoreElements() { | ||
| return iter.hasNext(); | ||
| } | ||
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| public URL nextElement() { | ||
| return iter.next(); | ||
| } | ||
| }; | ||
| } | ||
| } |
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