Here you can find the source of createURLClassLoader(String dirPath)
public final static URLClassLoader createURLClassLoader(String dirPath) throws IOException
//package com.java2s; /*// www.ja v a 2 s .co m * Copyright 2015 Async-IO.org * * Licensed 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. */ import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.JarURLConnection; import java.net.URL; import java.net.URLClassLoader; import java.util.Enumeration; import java.util.jar.JarEntry; import java.util.jar.JarFile; public class Main { public final static URLClassLoader createURLClassLoader(String dirPath) throws IOException { String path; File file; URL appRoot; URL classesURL; if (!dirPath.endsWith("/") && !dirPath.endsWith(".war") && !dirPath.endsWith(".jar")) { dirPath += File.separator; } //Must be a better way because that sucks! String separator = (System.getProperty("os.name").toLowerCase().startsWith("win") ? "/" : "//"); if (dirPath != null && (dirPath.endsWith(".war") || dirPath.endsWith(".jar"))) { file = new File(dirPath); appRoot = new URL("jar:file:" + separator + file.getCanonicalPath().replace('\\', '/') + "!/"); classesURL = new URL( "jar:file:" + separator + file.getCanonicalPath().replace('\\', '/') + "!/WEB-INF/classes/"); path = expand(appRoot); //DEBUG //classesURL = new URL("file:/" + path + "WEB-INF/classes/"); //appRoot = new URL("file:/" + path); } else { path = dirPath; classesURL = new URL("file://" + path + "WEB-INF/classes/"); appRoot = new URL("file://" + path); } String absolutePath = new File(path).getAbsolutePath(); URL[] urls; File libFiles = new File(absolutePath + File.separator + "WEB-INF" + File.separator + "lib"); int arraySize = 4; if (libFiles.exists() && libFiles.isDirectory()) { urls = new URL[libFiles.listFiles().length + arraySize]; for (int i = 0; i < libFiles.listFiles().length; i++) { urls[i] = new URL( "jar:file:" + separator + libFiles.listFiles()[i].toString().replace('\\', '/') + "!/"); } } else { urls = new URL[arraySize]; } urls[urls.length - 1] = classesURL; urls[urls.length - 2] = appRoot; urls[urls.length - 3] = new URL("file://" + path + "/WEB-INF/classes/"); urls[urls.length - 4] = new URL("file://" + path); return new URLClassLoader(urls, Thread.currentThread().getContextClassLoader()); } /** * Expand the jar file found at the specified URL into an unpacked * directory structure, and return the absolute pathname to the expanded * directory. * * @param jar URL of the web application archive to be expanded * (must start with "jar:") * @return Absolute path as in {@link java.io.File#getAbsolutePath()} of location where to find expanded jar. * @throws IllegalArgumentException if this is not a "jar:" URL * @throws IOException if an input/output error was encountered * during expansion */ public static String expand(URL jar) throws IOException { return expand(jar, System.getProperty("java.io.tmpdir")); } /** * Expand the jar file found at the specified URL into an unpacked * directory structure, and return the absolute pathname to the expanded * directory. * * @param jar URL of the web application archive to be expanded * (must start with "jar:") * @param workFolder the folder where the file will be expanded * @return Absolute path as in {@link java.io.File#getAbsolutePath()} of location where to find expanded jar. * @throws IllegalArgumentException if this is not a "jar:" URL * @throws IOException if an input/output error was encountered * during expansion */ public static String expand(URL jar, String workFolder) throws IOException { // Calculate the directory name of the expanded directory String pathname = jar.toString().replace('\\', '/'); if (pathname.endsWith("!/")) { pathname = pathname.substring(0, pathname.length() - 2); } int period = pathname.lastIndexOf('.'); if (period >= pathname.length() - 4) pathname = pathname.substring(0, period); int slash = pathname.lastIndexOf('/'); if (slash >= 0) { pathname = pathname.substring(slash + 1); } return expand(jar, pathname, workFolder); } /** * Expand the jar file found at the specified URL into an unpacked * directory structure, and return the absolute pathname to the expanded * directory. * * @param jar URL of the web application archive to be expanded * (must start with "jar:") * @param pathname Context path name for web application * @return Absolute path as in {@link java.io.File#getAbsolutePath()} of location where to find expanded jar. * @throws IllegalArgumentException if this is not a "jar:" URL * @throws IOException if an input/output error was encountered * during expansion */ public static String expand(URL jar, String pathname, String dirname) throws IOException { // Make sure that there is no such directory already existing File appBase = new File(dirname); File docBase = new File(appBase, pathname); // Create the new document base directory if (!docBase.mkdir()) { throw new IllegalStateException( String.format("Unable to create directory: %s", docBase.getAbsolutePath())); } // Expand the jar into the new document base directory JarURLConnection juc = (JarURLConnection) jar.openConnection(); juc.setUseCaches(false); JarFile jarFile = null; InputStream input = null; try { jarFile = juc.getJarFile(); Enumeration<JarEntry> jarEntries = jarFile.entries(); while (jarEntries.hasMoreElements()) { JarEntry jarEntry = jarEntries.nextElement(); String name = jarEntry.getName(); int last = name.lastIndexOf('/'); if (last >= 0) { File parent = new File(docBase, name.substring(0, last)); if (!parent.mkdirs()) { throw new IllegalStateException( String.format("Unable to create directory: %s", parent.getAbsolutePath())); } } if (name.endsWith("/")) { continue; } input = jarFile.getInputStream(jarEntry); expand(input, docBase, name); input.close(); input = null; } } catch (IOException e) { // If something went wrong, delete expanded dir to keep things // clean deleteDir(docBase); throw e; } finally { if (input != null) { try { input.close(); } catch (Throwable ignored) { } input = null; } if (jarFile != null) { try { jarFile.close(); } catch (Throwable ignored) { } jarFile = null; } } // Return the absolute path to our new document base directory return (docBase.getAbsolutePath()); } /** * Expand the specified input stream into the specified directory, creating * a file named from the specified relative path. * * @param input InputStream to be copied * @param docBase Document base directory into which we are expanding * @param name Relative pathname of the file to be created * @throws IOException if an input/output error occurs */ protected static void expand(InputStream input, File docBase, String name) throws IOException { File file = new File(docBase, name); BufferedOutputStream output = null; try { output = new BufferedOutputStream(new FileOutputStream(file)); byte buffer[] = new byte[2048]; while (true) { int n = input.read(buffer); if (n <= 0) break; output.write(buffer, 0, n); } } finally { if (output != null) { try { output.close(); } catch (IOException ignored) { // Ignore } } } } /** * Delete the specified directory, including all of its contents and * subdirectories recursively. * * @param dir File object representing the directory to be deleted */ public static boolean deleteDir(File dir) { String files[] = dir.list(); if (files == null) { files = new String[0]; } for (int i = 0; i < files.length; i++) { File file = new File(dir, files[i]); if (file.isDirectory()) { deleteDir(file); } else { if (!file.delete()) { throw new IllegalStateException( String.format("Unable to delete file: %s", file.getAbsolutePath())); } } } return dir.delete(); } }