satishd commented on a change in pull request #11390: URL: https://github.com/apache/kafka/pull/11390#discussion_r767425395
########## File path: clients/src/main/java/org/apache/kafka/common/utils/ChildFirstClassLoader.java ########## @@ -0,0 +1,131 @@ +/* + * 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.kafka.common.utils; + +import java.io.File; +import java.io.IOException; +import java.net.URL; +import java.net.URLClassLoader; +import java.util.ArrayList; +import java.util.Enumeration; +import java.util.Locale; +import java.util.NoSuchElementException; + +/** + * A class loader that looks for classes and resources in a specified class path first, before delegating to its parent + * class loader. + */ +public class ChildFirstClassLoader extends URLClassLoader { + static { + ClassLoader.registerAsParallelCapable(); + } + + /** + * @param classPath Class path string + * @param parent The parent classloader. If the required class / resource cannot be found in the given classPath, + * this classloader will be used to find the class / resource. + */ + public ChildFirstClassLoader(String classPath, ClassLoader parent) { + super(classpath2URLs(classPath), parent); + } + + static private URL[] classpath2URLs(String classPath) { + ArrayList<URL> urls = new ArrayList<>(); + for (String path : classPath.split(File.pathSeparator)) { + if (path == null || path.trim().isEmpty()) + continue; + File f = new File(path); + + if (path.endsWith("/*")) { + try { + File parent = new File(new File(f.getCanonicalPath()).getParent()); + if (parent.isDirectory()) { + File[] files = parent.listFiles((dir, name) -> { + String lower = name.toLowerCase(Locale.ROOT); + return lower.endsWith(".jar") || lower.endsWith(".zip"); + }); + if (files != null) { + for (File jarFile : files) { + urls.add(jarFile.getCanonicalFile().toURI().toURL()); + } + } + } + } catch (IOException e) { + } + } else if (f.exists()) { + try { + urls.add(f.getCanonicalFile().toURI().toURL()); + } catch (IOException e) { + } + } + } + return urls.toArray(new URL[0]); + } + + @Override + protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException { + synchronized (getClassLoadingLock(name)) { + Class<?> c = findLoadedClass(name); + + if (c == null) { + try { + c = findClass(name); + } catch (ClassNotFoundException e) { + // try parent + c = super.loadClass(name, false); + } + } + + if (resolve) + resolveClass(c); + + return c; + } + } + + @Override + public URL getResource(String name) { + URL url = findResource(name); + if (url == null) { + // try parent + url = super.getResource(name); + } + return url; + } + + @Override + public Enumeration<URL> getResources(String name) throws IOException { + Enumeration<URL> urls1 = findResources(name); + Enumeration<URL> urls2 = getParent() != null ? getParent().getResources(name) : null; Review comment: It checks if the given resource exists within this class loader first, it delegates to the parent classloader if it is not found in this class loader. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
