Java WatchService和SwingWorker:如何正确执行?
WatchService听起来像是一个激动人心的想法。。。不幸的是,它似乎和教程/api plus中警告的一样低级,并不真正适合Swing事件模型(或者我遗漏了一些明显的东西,不是零概率) 以代码(简化为只处理一个目录)为例,我基本上以Java WatchService和SwingWorker:如何正确执行?,java,swing,nio,swingworker,watchservice,Java,Swing,Nio,Swingworker,Watchservice,WatchService听起来像是一个激动人心的想法。。。不幸的是,它似乎和教程/api plus中警告的一样低级,并不真正适合Swing事件模型(或者我遗漏了一些明显的东西,不是零概率) 以代码(简化为只处理一个目录)为例,我基本上以 扩展SwingWorker 在构造函数中进行注册 将无休止的等待钥匙的循环放在后台 通过key.pollEvents()检索时发布每个WatchEvent 通过将已删除/创建的文件作为newValue触发propertyChangeEvents来处理区块 @S
- 扩展SwingWorker
- 在构造函数中进行注册
- 将无休止的等待钥匙的循环放在后台
- 通过key.pollEvents()检索时发布每个WatchEvent
- 通过将已删除/创建的文件作为newValue触发propertyChangeEvents来处理区块
@SuppressWarnings("unchecked") public class FileWorker extends SwingWorker<Void, WatchEvent<Path>> { public static final String DELETED = "deletedFile"; public static final String CREATED = "createdFile"; private Path directory; private WatchService watcher; public FileWorker(File file) throws IOException { directory = file.toPath(); watcher = FileSystems.getDefault().newWatchService(); directory.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY); } @Override protected Void doInBackground() throws Exception { for (;;) { // wait for key to be signalled WatchKey key; try { key = watcher.take(); } catch (InterruptedException x) { return null; } for (WatchEvent<?> event : key.pollEvents()) { WatchEvent.Kind<?> kind = event.kind(); // TBD - provide example of how OVERFLOW event is handled if (kind == OVERFLOW) { continue; } publish((WatchEvent<Path>) event); } // reset key return if directory no longer accessible boolean valid = key.reset(); if (!valid) { break; } } return null; } @Override protected void process(List<WatchEvent<Path>> chunks) { super.process(chunks); for (WatchEvent<Path> event : chunks) { WatchEvent.Kind<?> kind = event.kind(); Path name = event.context(); Path child = directory.resolve(name); File file = child.toFile(); if (StandardWatchEventKinds.ENTRY_DELETE == kind) { firePropertyChange(DELETED, null, file); } else if (StandardWatchEventKinds.ENTRY_CREATE == kind) { firePropertyChange(CREATED, null, file); } } } }
@SuppressWarnings(“未选中”) 公共类FileWorker扩展SwingWorker{ 公共静态最终字符串DELETED=“deletedFile”; 创建的公共静态最终字符串=“createdFile”; 专用路径目录; 私人观察者; 公共文件工作者(文件)引发IOException{ directory=file.toPath(); watcher=FileSystems.getDefault().newWatchService(); 目录。注册(观察者、条目创建、条目删除、条目修改); } @凌驾 受保护的Void doInBackground()引发异常{ 对于(;;){ //等待钥匙发出信号 监视键; 试一试{ key=watcher.take(); }捕捉(中断异常x){ 返回null; } for(WatchEvent事件:key.pollEvents()){ WatchEvent.Kind-Kind=event.Kind(); //TBD-提供如何处理溢出事件的示例 如果(种类==溢出){ 继续; } 发布((监视事件)事件); } //如果目录不再可访问,则重置键返回 布尔有效值=key.reset(); 如果(!有效){ 打破 } } 返回null; } @凌驾 受保护的无效进程(列表块){ 超级进程(块); for(WatchEvent事件:块){ WatchEvent.Kind-Kind=event.Kind(); 路径名=event.context(); Path child=directory.resolve(名称); File=child.toFile(); if(StandardWatchEventTypes.ENTRY_DELETE==种类){ firePropertyChange(已删除,空,文件); }else if(StandardWatchEventTypes.ENTRY_CREATE==种类){ firePropertyChange(已创建,空,文件); } } } }
String testDir = "D:\\scans\\library";
File directory = new File(testDir);
final DefaultListModel<File> model = new DefaultListModel<File>();
for (File file : directory.listFiles()) {
model.addElement(file);
}
final FileWorker worker = new FileWorker(directory);
PropertyChangeListener l = new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (FileWorker.DELETED == evt.getPropertyName()) {
model.removeElement(evt.getNewValue());
} else if (FileWorker.CREATED == evt.getPropertyName()) {
model.addElement((File) evt.getNewValue());
}
}
};
worker.addPropertyChangeListener(l);
JXList list = new JXList(model);
String testDir=“D:\\scans\\library”;
文件目录=新文件(testDir);
最终DefaultListModel=新DefaultListModel();
对于(文件:directory.listFiles()){
模型补遗(文件);
}
最终文件工作者=新文件工作者(目录);
PropertyChangeListener l=新的PropertyChangeListener(){
@凌驾
公共作废属性更改(属性更改事件evt){
if(FileWorker.DELETED==evt.getPropertyName()){
model.removelement(evt.getNewValue());
}else if(FileWorker.CREATED==evt.getPropertyName()){
model.addElement((文件)evt.getNewValue());
}
}
};
worker.addPropertyChangeListener(l);
JXList列表=新JXList(型号);
看起来不错,但我觉得不舒服
- 把自己打扮成线程不可知论者:到目前为止,我看到的所有示例代码片段都会使用watcher.take()阻止等待的线程。为什么要这样做?至少会有一些人使用watcher.poll()并睡一会儿
- SwingWorker发布方法似乎不太合适:目前还可以,因为我在尝试查看多个目录(如最初的WatchDir示例中)时只查看一个目录(不想走错太远的方向:)有多个键以及与其中一个键相关的WatchEvent。要解析路径,我需要事件和键正在监视的目录[A]。但只能传递一个。不过,很可能是逻辑分布错误
刚刚接受了我自己的回答-将谦恭地回复,如果有人有合理的反对意见,因为您的后台线程完全用于观看,这是正确的选择。它有效地隐藏了实现,可以转发或轮询。例如,如果您的后台线程也eded检查与
监视服务
串联的其他队列
附录:由于具有状态,可能不应将其转发到process()
。a的路径是“在watch服务中注册的目录和
@SuppressWarnings("unchecked")
public class FileWorker extends SwingWorker<Void, PropertyChangeEvent> {
public static final String FILE_DELETED = StandardWatchEventKinds.ENTRY_DELETE.name();
public static final String FILE_CREATED = StandardWatchEventKinds.ENTRY_CREATE.name();
public static final String FILE_MODIFIED = StandardWatchEventKinds.ENTRY_MODIFY.name();
// final version will keep a map of keys/directories (just as in the tutorial example)
private Path directory;
private WatchService watcher;
public FileWorker(File file) throws IOException {
directory = file.toPath();
watcher = FileSystems.getDefault().newWatchService();
directory.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
}
@Override
protected Void doInBackground() throws Exception {
for (;;) {
// wait for key to be signalled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return null;
}
for (WatchEvent<?> event : key.pollEvents()) {
WatchEvent.Kind<?> kind = event.kind();
// TBD - provide example of how OVERFLOW event is handled
if (kind == OVERFLOW) {
continue;
}
publish(createChangeEvent((WatchEvent<Path>) event, key));
}
// reset key return if directory no longer accessible
boolean valid = key.reset();
if (!valid) {
break;
}
}
return null;
}
/**
* Creates and returns the change notification. This method is called from the
* worker thread while looping through the events as received from the Watchkey.
*
* @param event
* @param key
*/
protected PropertyChangeEvent createChangeEvent(WatchEvent<Path> event, WatchKey key) {
Path name = event.context();
// real world will lookup the directory from the key/directory map
Path child = directory.resolve(name);
PropertyChangeEvent e = new PropertyChangeEvent(this, event.kind().name(), null, child.toFile());
return e;
}
@Override
protected void process(List<PropertyChangeEvent> chunks) {
super.process(chunks);
for (PropertyChangeEvent event : chunks) {
getPropertyChangeSupport().firePropertyChange(event);
}
}
}