Java tutorial
/* * 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.accumulo.start.classloader; import java.io.File; import java.io.IOException; import java.net.MalformedURLException; import java.net.URI; import java.net.URISyntaxException; import java.net.URL; import java.net.URLClassLoader; import java.util.ArrayList; import java.util.Map; import java.util.regex.Matcher; import java.util.regex.Pattern; import org.apache.commons.configuration.PropertiesConfiguration; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import edu.umd.cs.findbugs.annotations.SuppressFBWarnings; public class AccumuloClassLoader { public static final String GENERAL_CLASSPATHS = "general.classpaths"; private static URL accumuloConfigUrl; private static URLClassLoader classloader; private static final Logger log = LoggerFactory.getLogger(AccumuloClassLoader.class); static { String configFile = System.getProperty("accumulo.properties", "accumulo.properties"); if (configFile.startsWith("file://")) { try { File f = new File(new URI(configFile)); if (f.exists() && !f.isDirectory()) { accumuloConfigUrl = f.toURI().toURL(); } else { log.warn("Failed to load Accumulo configuration from " + configFile); } } catch (URISyntaxException | MalformedURLException e) { log.warn("Failed to load Accumulo configuration from " + configFile, e); } } else { accumuloConfigUrl = AccumuloClassLoader.class.getClassLoader().getResource(configFile); if (accumuloConfigUrl == null) log.warn("Failed to load Accumulo configuration '{}' from classpath", configFile); } if (accumuloConfigUrl != null) log.debug("Using Accumulo configuration at {}", accumuloConfigUrl.getFile()); } /** * Returns value of property in accumulo.properties file, otherwise default value * * @param propertyName * Name of the property to pull * @param defaultValue * Value to default to if not found. * @return value of property or default */ public static String getAccumuloProperty(String propertyName, String defaultValue) { if (accumuloConfigUrl == null) { log.warn("Using default value '{}' for '{}' as there is no Accumulo configuration on classpath", defaultValue, propertyName); return defaultValue; } try { PropertiesConfiguration config = new PropertiesConfiguration(); config.setDelimiterParsingDisabled(true); config.setThrowExceptionOnMissing(false); config.load(accumuloConfigUrl); String value = config.getString(propertyName); if (value != null) return value; return defaultValue; } catch (Exception e) { throw new IllegalStateException( "Failed to look up property " + propertyName + " in " + accumuloConfigUrl.getFile(), e); } } /** * Replace environment variables in the classpath string with their actual value */ public static String replaceEnvVars(String classpath, Map<String, String> env) { Pattern envPat = Pattern.compile("\\$[A-Za-z][a-zA-Z0-9_]*"); Matcher envMatcher = envPat.matcher(classpath); while (envMatcher.find(0)) { // name comes after the '$' String varName = envMatcher.group().substring(1); String varValue = env.get(varName); if (varValue == null) { varValue = ""; } classpath = (classpath.substring(0, envMatcher.start()) + varValue + classpath.substring(envMatcher.end())); envMatcher.reset(classpath); } return classpath; } /** * Populate the list of URLs with the items in the classpath string */ @SuppressFBWarnings(value = "PATH_TRAVERSAL_IN", justification = "class path configuration is controlled by admin, not unchecked user input") private static void addUrl(String classpath, ArrayList<URL> urls) throws MalformedURLException { classpath = classpath.trim(); if (classpath.length() == 0) return; classpath = replaceEnvVars(classpath, System.getenv()); // Try to make a URI out of the classpath URI uri = null; try { uri = new URI(classpath); } catch (URISyntaxException e) { // Not a valid URI } if (uri == null || !uri.isAbsolute() || (uri.getScheme() != null && uri.getScheme().equals("file://"))) { // Then treat this URI as a File. // This checks to see if the url string is a dir if it expand and get all jars in that // directory final File extDir = new File(classpath); if (extDir.isDirectory()) urls.add(extDir.toURI().toURL()); else { if (extDir.getParentFile() != null) { File[] extJars = extDir.getParentFile() .listFiles((dir, name) -> name.matches("^" + extDir.getName())); if (extJars != null && extJars.length > 0) { for (File jar : extJars) urls.add(jar.toURI().toURL()); } else { log.debug("ignoring classpath entry {}", classpath); } } else { log.debug("ignoring classpath entry {}", classpath); } } } else { urls.add(uri.toURL()); } } private static ArrayList<URL> findAccumuloURLs() throws IOException { String cp = getAccumuloProperty(GENERAL_CLASSPATHS, null); if (cp == null) return new ArrayList<>(); log.warn("'{}' is deprecated but was set to '{}' ", GENERAL_CLASSPATHS, cp); String[] cps = replaceEnvVars(cp, System.getenv()).split(","); ArrayList<URL> urls = new ArrayList<>(); for (String classpath : cps) { if (!classpath.startsWith("#")) { addUrl(classpath, urls); } } return urls; } public static synchronized ClassLoader getClassLoader() throws IOException { if (classloader == null) { ArrayList<URL> urls = findAccumuloURLs(); ClassLoader parentClassLoader = AccumuloClassLoader.class.getClassLoader(); log.debug("Create 2nd tier ClassLoader using URLs: {}", urls); classloader = new URLClassLoader(urls.toArray(new URL[urls.size()]), parentClassLoader) { @Override protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException { if (name.startsWith("org.apache.accumulo.start.classloader.vfs")) { Class<?> c = findLoadedClass(name); if (c == null) { try { // try finding this class here instead of parent findClass(name); } catch (ClassNotFoundException e) { } } } return super.loadClass(name, resolve); } }; } return classloader; } }