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153 lines (136 loc) · 3.98 KB
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-----------------------
文件监视 |
-----------------------
# 监视某个目录下文件的
* 创建
* 删除
* 修改
# 涉及类库
WatchService
WatchKey
WatchEvent<?>
WatchEvent.Kind
# 事件
StandardWatchEventKinds.ENTRY_CREATE 文件创建
StandardWatchEventKinds.ENTRY_DELETE 文件删除
StandardWatchEventKinds.ENTRY_MODIFY 文件修改
StandardWatchEventKinds.OVERFLOW 事件丢失，一般不关注
-----------------------
WatchService |
-----------------------
# 接口方法
@Override
void close() throws IOException;
WatchKey poll();
WatchKey poll(long timeout, TimeUnit unit) throws InterruptedException;
WatchKey take() throws InterruptedException;
-----------------------
WatchKey |
-----------------------
# 接口方法
boolean isValid();
List<WatchEvent<?>> pollEvents();
boolean reset();
void cancel();
Watchable watchable();
-----------------------
WatchEvent |
-----------------------
# 接口方法
Kind<T> kind();
int count();
T context();
# 内部接口
public static interface Kind<T> {
String name();
Class<T> type();
}
public static interface Modifier {
String name();
}
-----------------------
Demo |
-----------------------
//WatchService 是线程安全的，跟踪文件事件的服务，一般是用独立线程启动跟踪
public static void watchRNDir(Path path) throws Exception {
//创建 WatchService 对象
WatchService watchService = FileSystems.getDefault().newWatchService();
//给path路径加上文件观察服务
path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
// 开始监视路径
while (true) {
//线程阻塞
final WatchKey key = watchService.take();
//获取事件集合
List<WatchEvent<?>> watchEventList = key.pollEvents();
//遍历
for (WatchEvent<?> watchEvent : watchEventList) {
// 获取事件
final WatchEvent.Kind<?> kind = watchEvent.kind();
// handle OVERFLOW event
if (kind == StandardWatchEventKinds.OVERFLOW) {
continue;
}
//创建事件
if (kind == StandardWatchEventKinds.ENTRY_CREATE) {
}
//修改事件
if (kind == StandardWatchEventKinds.ENTRY_MODIFY) {
}
//删除事件
if (kind == StandardWatchEventKinds.ENTRY_DELETE) {
}
//把当前事件强制转换泛型为 Path 的事件
final WatchEvent<Path> watchEventPath = (WatchEvent<Path>) watchEvent;
//获取事件文件名称
final Path filename = watchEventPath.context();
// print it out
System.out.println(kind + " -> " + filename);
}
// reset the keyf
boolean valid = key.reset();
// exit loop if the key is not valid (if the directory was
// deleted, for
if (!valid) {
break;
}
}
}
------------------------------------
WatchService |
------------------------------------
# 构建
WatchService watchService = FileSystems.getDefault().newWatchService();
# 方法
WatchKey take();
* 检索并移除下一个watch key。若没有可检索的则阻塞。
------------------------------------
WatchKey |
------------------------------------
# 构建
通过 WatchService 实例的 take()方法获取
# 方法
List<WatchEvent<?>> pollEvents();
* 检索并移除所有该watch key
------------------------------------
WatchEvent |
------------------------------------
# 构建
# 方法
Kind<?> kind();
* 返回事件种类
------------------------------------
Kind |
------------------------------------
# 方法
String name();
* 返回事件的名称
------------------------------------
StandardWatchEventKinds |
------------------------------------
# 事件类
# 静态字段
OVERFLOW
ENTRY_CREATE
ENTRY_DELETE
ENTRY_MODIFY