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。

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：

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