Java tutorial
/* ============================================================================ * * FILE: JarModuleLoader.java * The MIT License (MIT) Copyright (c) 2016 Sutanu Dalui Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. * * ============================================================================ */ package com.reactive.hzdfs.dll; import java.io.File; import java.io.IOException; import java.nio.file.ClosedWatchServiceException; import java.nio.file.FileVisitResult; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; import java.nio.file.SimpleFileVisitor; import java.nio.file.StandardWatchEventKinds; import java.nio.file.WatchEvent; import java.nio.file.WatchKey; import java.nio.file.WatchService; import java.nio.file.attribute.BasicFileAttributes; import java.util.HashSet; import java.util.LinkedHashSet; import java.util.Set; import java.util.jar.JarFile; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.BeanInitializationException; /** * Class to register libraries (jar files) as JAX RS services, by linking and * loading them to the application classpath. This class will register a file watcher * to listen for new jar files. */ class JarModuleLoader implements Runnable { private static final Logger log = LoggerFactory.getLogger(JarModuleLoader.class); private final Path root; /** * * @param path root directory */ public JarModuleLoader(String path) { root = Paths.get(path); jarLoader = new JarClassLoader(); } /** * * @param f */ public JarModuleLoader(File f) { this(f.getAbsolutePath()); } private WatchService watcher; void init() { log.info("[JAR Loader] Registering file change listeners on root dir- " + root); try { watcher = root.getFileSystem().newWatchService(); } catch (Exception e) { throw new BeanInitializationException("Unable to register file watcher", e); } setInitialFiles(walkDirectory(root)); for (File f : getInitialFiles()) { loadDynamicLibrary(f); } new Thread(this, "JAR Loader-Worker").start(); log.info("[JAR Loader] Loaded dynamic modules on startup.."); } private Set<File> initialFiles = new HashSet<>(); private void registerWatch(Path dir) throws IOException { if (log.isDebugEnabled()) { log.debug("registering: " + dir + " for file events"); } dir.register(watcher, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY); } private Set<File> walkDirectory(Path directory) { final Set<File> walkedFiles = new LinkedHashSet<File>(); try { registerWatch(directory); Files.walkFileTree(directory, new SimpleFileVisitor<Path>() { @Override public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException { FileVisitResult fileVisitResult = super.preVisitDirectory(dir, attrs); registerWatch(dir); return fileVisitResult; } @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException { FileVisitResult fileVisitResult = super.visitFile(file, attrs); if (isJarFile(file.toFile())) walkedFiles.add(file.toFile()); return fileVisitResult; } }); } catch (IOException e) { log.error("Failed to walk directory: " + directory.toString(), e); } return walkedFiles; } private static boolean isJarFile(File f) { try (JarFile j = new JarFile(f)) { return true; } catch (IOException e) { } return false; } private final JarClassLoader jarLoader; private volatile boolean stopRequested; private void loadDynamicLibrary(File f) { try { jarLoader.addJar(f); log.info("[JAR Loader] Loaded classes from: " + f.getName()); } catch (Exception e) { log.error("[JAR Loader] Unable to load classes from jar", e); } } @Override public void run() { while (!stopRequested) { try { Set<File> files = filesFromEvents(); for (File f : files) { loadDynamicLibrary(f); } } catch (ClosedWatchServiceException e) { if (!stopRequested) log.error("[JAR Loader] Watch service closed unexpectedly!", e); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } public void stop() { stopRequested = true; try { watcher.close(); } catch (IOException e) { log.debug(e.getMessage()); } } private Set<File> filesFromEvents() throws InterruptedException { WatchKey key = watcher.take(); Set<File> files = new LinkedHashSet<File>(); if (key != null && key.isValid()) { for (WatchEvent<?> event : key.pollEvents()) { if (event.kind() == StandardWatchEventKinds.ENTRY_CREATE || event.kind() == StandardWatchEventKinds.ENTRY_MODIFY) { Path item = (Path) event.context(); File file = new File( ((Path) key.watchable()).toAbsolutePath() + File.separator + item.getFileName()); if (log.isDebugEnabled()) { log.debug("Watch Event: " + event.kind() + ": " + file); } if (isJarFile(file)) { files.add(file); } else log.warn("[JAR Loader] Ignoring file:- " + file); } } key.reset(); } return files; } public Set<File> getInitialFiles() { return initialFiles; } public void setInitialFiles(Set<File> initialFiles) { this.initialFiles.addAll(initialFiles); } }