[英]Unknown Exception? java.nio.file.FileSystemException: Invalid exchange
[英]Renaming a file throwing Exception in thread “main” java.nio.file.FileSystemException:
我正在尋找使用WatchService創建新文件的目錄。 每當創建新文件或進入該目錄時,我都需要更改該文件的名稱。
我有以下代碼
Path pathfolder=Paths.get("D:\\tempm\\watch");
WatchService watcherService=FileSystems.getDefault().newWatchService();
pathfolder.register(watcherService, StandardWatchEventKinds.ENTRY_CREATE);
System.out.println("Watching that directory");
boolean valid=true;
do{
WatchKey watchKey=watcherService.take();
for(WatchEvent<?> event:watchKey.pollEvents()){
WatchEvent.Kind kind=event.kind();
if(StandardWatchEventKinds.ENTRY_CREATE.equals(event.kind())){
final String fileName=event.context().toString();
if(fileName.endsWith(".jar")){
System.out.println("File created--"+fileName);
File oldFileName=new File("D:\\tempm\\watch\\"+fileName);
File destFile=new File("D:\\tempm\\watch\\"+fileName.substring(0,fileName.lastIndexOf("."))+"_processing.jar");
File path=new File("D:\\tempm\\watch\\");
if(!fileName.contains("_processing")){
Files.move(oldFileName.toPath(), destFile.toPath(),StandardCopyOption.ATOMIC_MOVE,StandardCopyOption.REPLACE_EXISTING); //Line Number 45
FileDeleteStrategy.FORCE.delete(oldFileName);
System.out.println("Old file deleted");
}
}
}
}
valid=watchKey.reset();
}while(valid);
當我第一次將文件粘貼到該目錄中時,它已成功重命名;如果我第二次添加任何文件,它將引發異常。我不知道為什么會給出該異常。需要一些幫助。
我的輸出
Watching that directory
File created--dom4j.jar
Old file deleted
File created--dom4j_processing.jar
File created--watchplc.jar
Exception in thread "main" java.nio.file.FileSystemException: D:\tempm\watch\watchplc.jar -> D:\tempm\watch\watchplc_processing.jar: The process cannot access the file because it is being used by another process.
at sun.nio.fs.WindowsException.translateToIOException(Unknown Source)
at sun.nio.fs.WindowsException.rethrowAsIOException(Unknown Source)
at sun.nio.fs.WindowsFileCopy.move(Unknown Source)
at sun.nio.fs.WindowsFileSystemProvider.move(Unknown Source)
at java.nio.file.Files.move(Unknown Source)
at ext.gt.test.MonitorDirectory.main(MonitorDirectory.java:45)
您的程序失敗,因為StandardWatchEventKinds.ENTRY_CREATE
僅告訴您已創建文件,而不是告訴進程已停止寫入文件或釋放文件句柄。 您可以通過自己創建一個簡單的程序來復制錯誤。
public class FileCreator
{
public static void main(String... args)
{
new FileCreator().go();
}
public void go()
{
FileWriter fileWriter = null;
try
{
File file = new File("d:/tempm/watch/" + System.currentTimeMillis() + ".jar");
fileWriter = new FileWriter(file);
for (int counter = 0; counter < 100; counter++)
{
// first write
fileWriter.write(String.valueOf(System.nanoTime()));
}
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if(fileWriter != null)
{
try
{
// data is flushed and file handles are closed
fileWriter.flush();
fileWriter.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
}
請注意,一旦遇到第一個write()
,就會立即創建一個文件。 該程序仍然具有文件的句柄,並繼續對其進行寫入,直到刷新並關閉流為止。 您的其他程序在流關閉該文件之前,先將其移走。
在嘗試move
文件之前,您需要一個系統來告訴您文件是否已完全寫入要查看的目錄。
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