Java实现系统目录实时监听更新。

SDK1.7新增的nio WatchService能完美解决这个问题。美中不足是如果部署在window系统下会出现莫名其妙的文件夹占用异常导致子目录监听失效，linux下则完美运行。这个问题着实让人头疼。如果有童鞋找到问题根源请一起探讨。

这里简单的列出用Servlet实现的基本类供大家参考。首先是核心的实现类。

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package com.event;   import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE; import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE; import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY; import static java.nio.file.StandardWatchEventKinds.OVERFLOW;   import java.io.File; import java.io.IOException; import java.nio.file.FileSystems; import java.nio.file.Path; import java.nio.file.Paths; import java.nio.file.WatchEvent; import java.nio.file.WatchEvent.Kind; import java.nio.file.WatchKey; import java.nio.file.WatchService; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Observable; import java.util.concurrent.Executor; import java.util.concurrent.Executors; import java.util.concurrent.FutureTask;   import org.apache.poi.ss.formula.ptg.Ptg;   public class DirectoryWatcher extends Observable { // 存储监听主键和监听目录的对应 private static Map<WatchKey, String> pathMap = null; private WatchService watcher;// 目录监听服务 private WatchKey key;// 目录对应的监听key private Executor executor = Executors.newSingleThreadExecutor(); FutureTask<Integer> task = new FutureTask<Integer>(() -> { processEvents(); return Integer.valueOf(0); });   @SuppressWarnings("unchecked") static <T> WatchEvent<T> cast(WatchEvent<?> event) { return (WatchEvent<T>) event; }   public DirectoryWatcher(String dir) throws IOException { watcher = FileSystems.getDefault().newWatchService(); pathMap = new HashMap<WatchKey, String>(); registDirs(dir); }   private void registDirs(String dir) throws IOException { List<File> dirs = new ArrayList<File>(); File dirRoot = new File(dir); getAllDirs(dirRoot, dirs); // 循环路径下所有目录填充map for (File eveDir : dirs) { Path path = Paths.get(eveDir.getAbsolutePath()); // 监控目录内文件的更新、创建和删除事件 try { key = path.register(watcher, ENTRY_CREATE, ENTRY_DELETE); pathMap.put(key, eveDir.getAbsolutePath()); } catch (IOException e) { e.printStackTrace(); } } }   // 递归获取所有目录 private void getAllDirs(File dir, List<File> dirs) { if (dir.isDirectory()) { dirs.add(dir); File[] fs = dir.listFiles(); for (File f : fs) { getAllDirs(f, dirs); } } }   /** * 启动监控过程 */ public void execute() { // 通过线程池启动一个额外的线程加载Watching过程 executor.execute(task); }   /** * 关闭后的对象无法重新启动 */ public void shutdown() throws IOException { watcher.close(); executor = null; }   // * 监控文件系统事件 void processEvents() { while (true) { // 等待直到获得事件信号 WatchKey signal; try { signal = watcher.take(); } catch (InterruptedException x) { return; } for (WatchEvent<?> event : signal.pollEvents()) { Kind<?> kind = event.kind(); if (kind == OVERFLOW) { continue; } WatchEvent<Path> ev = cast(event);   Path name = ev.context(); String fileName = name.getFileName().toString(); String dirPath = pathMap.get(signal) + "/" + fileName; if (kind.name().equals("ENTRY_CREATE") && fileName.indexOf(".") == -1) { Path path = Paths.get(dirPath); try { key = path .register(watcher, ENTRY_CREATE, ENTRY_DELETE); pathMap.put(key, dirPath); } catch (IOException e) { e.printStackTrace(); } } else if (kind.name().equals("ENTRY_DELETE") && fileName.indexOf(".") == -1) { pathMap.remove(key); key.cancel(); }   System.out.println("event:" + kind.name() + ";file:" + dirPath); FileWatchEventArgs args = new FileWatchEventArgs(kind.name(), pathMap.get(signal), fileName); notifiy(args);// 通知所有观察者事件变更 } // 为监控下一个通知做准备 signal.reset(); } }   // * 通知外部各个Observer目录有新的事件更新 void notifiy(FileWatchEventArgs args) { // 标注目录已经被做了更改 setChanged(); // 主动通知各个观察者目标对象状态的变更 notifyObservers(args); } }

来自CODE的代码片

DirectoryWatcher.java

Servlet的实现类：

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package com.demo;   import java.io.File; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Observable; import java.util.Observer;   import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;   import com.entry.VedioFile; import com.event.DirectoryWatcher; import com.event.FileWatchEventArgs;   public class GetList extends HttpServlet implements Observer {   private static final long serialVersionUID = 3715567236188574915L; private String PATH; private String JsonTreeStr = null; private static List<VedioFile> vedioFileList; private static ThreadLocal<String> SubRequestURL = new ThreadLocal<String>();   public static ThreadLocal<String> getSubRequestURL() { return SubRequestURL; }   public static List<VedioFile> getVedioFileList() { return vedioFileList; }   public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PATH = request.getServletContext().getRealPath("/") + "/curse";   request.getRequestDispatcher("/WEB-INF/index.jsp").forward(request, response); }   public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if (vedioFileList == null) { PATH = request.getServletContext().getRealPath("/") + "curse"; System.out.println(PATH); setVedioFileList(); // 建立目录监听，注册观察者为本身 DirectoryWatcher dw = new DirectoryWatcher(PATH); dw.addObserver(this); dw.execute(); }   SubRequestURL .set(request.getRequestURL().toString().split("getList")[0]); JsonTreeStr = vedioFileList.toString(); response.setContentType("text/xml;charset=utf-8"); response.setHeader("Cache-Control", "no-cache"); response.getWriter().write(JsonTreeStr); }   @Override // 实现Observer观察者接口，接收通知 public void update(Observable o, Object arg) { FileWatchEventArgs args = (FileWatchEventArgs) arg;   String name = args.getName(); String kind = args.getKind(); String dir = args.getDir();   File file = new File(dir + File.separator + name); if (kind.equals("ENTRY_CREATE")) { addVedioFile(file); } else if (kind.equals("ENTRY_DELETE")) { removeVedioFile(file); }   }   private void removeVedioFile(File file) { VedioFile nowVf = getNowVedioFile(file); if (nowVf != null) { for (int i = vedioFileList.size() - 1; i >= 0; i--) { if (nowVf.getPath() .equals(vedioFileList.get(i).getParentPath())) { vedioFileList.remove(i); } } vedioFileList.remove(nowVf); } }   private VedioFile getNowVedioFile(File file) { VedioFile nowVf = null; for (VedioFile vf : vedioFileList) { if (file.getAbsolutePath().equals(vf.getPath())) { nowVf = vf; break; } } return nowVf; }   private void setVedioFileList() { File file = new File(PATH); vedioFileList = new ArrayList<VedioFile>(); getVedioFiles(file, vedioFileList); }   private void getVedioFiles(File file, List<VedioFile> vfs) { if (file.isDirectory()) { File[] files = file.listFiles(); for (File f : files) { getVedioFiles(f, vfs); } } addVedioFile(file); }   private void addVedioFile(File file) { VedioFile vf = new VedioFile(); vf.setParentPath(file.getParent()); vf.setPath(file.getAbsolutePath()); vf.setName(file.getName()); if (file.getName().toLowerCase().endsWith(".mp4")) { vf.setUrl("vedio?url=" + MD5Utils.md5(vf.getPath())); } vedioFileList.add(vf); } }

来自CODE的代码片

GetList.java

 转：http://blog.csdn.net/feiying2j/article/details/50719648

附上源码下载地址：

http://download.csdn.net/detail/feiying2j/9439698