SDK1.7新增的nio WatchService能完美解決這個問題。美中不足是如果部署在window系統下會出現莫名其妙的文件夾占用異常導致子目錄監聽失效，linux下則完美運行。這個問題着實讓人頭疼。如果有童鞋找到問題根源請一起探討。
這里簡單的列出用Servlet實現的基本類供大家參考。首先是核心的實現類。
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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 {
// 存儲監聽主鍵和監聽目錄的對應
private static Map<WatchKey, String> pathMap = null;
private WatchService watcher;// 目錄監聽服務
private WatchKey key;// 目錄對應的監聽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);
// 循環路徑下所有目錄填充map
for (File eveDir : dirs) {
Path path = Paths.get(eveDir.getAbsolutePath());
// 監控目錄內文件的更新、創建和刪除事件
try {
key = path.register(watcher, ENTRY_CREATE, ENTRY_DELETE);
pathMap.put(key, eveDir.getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
}
}
}
// 遞歸獲取所有目錄
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);
}
}
}
/**
* 啟動監控過程
*/
public void execute() {
// 通過線程池啟動一個額外的線程加載Watching過程
executor.execute(task);
}
/**
* 關閉后的對象無法重新啟動
*/
public void shutdown() throws IOException {
watcher.close();
executor = null;
}
// * 監控文件系統事件
void processEvents() {
while (true) {
// 等待直到獲得事件信號
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);// 通知所有觀察者事件變更
}
// 為監控下一個通知做准備
signal.reset();
}
}
// * 通知外部各個Observer目錄有新的事件更新
void notifiy(FileWatchEventArgs args) {
// 標注目錄已經被做了更改
setChanged();
// 主動通知各個觀察者目標對象狀態的變更
notifyObservers(args);
}
}
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來自CODE的代碼片
DirectoryWatcher.java
Servlet的實現類：
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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();
// 建立目錄監聽，注冊觀察者為本身
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
// 實現Observer觀察者接口，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);
}
}
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來自CODE的代碼片
GetList.java
轉：http://blog.csdn.net/feiying2j/article/details/50719648
附上源碼下載地址：
http://download.csdn.net/detail/feiying2j/9439698