在Java中写锁定

Question

我有一个文件说text.csv从我的Java程序试图读取/写入。

有没有办法在Java中检测此文件是否打开，以便在文件被某些用户通过“双击”打开时进行写入？如果是这样，怎么样？我在寻找这样的代码：

if(isOpenForWrite(File file){ 
//say text.csv is already opened ... 
} 

任何有用的文档或其他资源是值得欢迎的。检查此

Answer 1

最好的办法是检查是否可以重命名文件

String fileName = "C:\\Text.xlsx"; 
File file = new File(fileName); 

// try to rename the file with the same name 
File sameFileName = new File(fileName); 

if(file.renameTo(sameFileName)){ 
    // if the file is renamed 
    System.out.println("file is closed");  
}else{ 
    // if the file didnt accept the renaming operation 
    System.out.println("file is opened"); 
} 

或使用Apache通用IO库

Answer 2

我会用FileChannel.lock做到这一点。

try { // Get a file channel for the file 
    File file = new File("text.csv"); 
    FileChannel channel = new RandomAccessFile(file, "rw").getChannel(); 

    // Blocks until it can retrieve the lock. 
    FileLock lock = channel.lock(); 
    // Try acquiring the lock without blocking. 
    // lock is null or exception if the file is already locked. 

    try { 
     lock = channel.tryLock(); 
    } catch (OverlappingFileLockException e){} 


    lock.release(); // Close the file 
    channel.close(); 
} catch (Exception e) { 
} 

Answer 3

来源：Java: Check if file is already open

使用此，我发现这个上面吩咐链接

boolean isFileUnlocked = false; 
    try { 
    org.apache.commons.io.FileUtils.touch(yourFile); 
    isFileUnlocked = true; 
    } catch (IOException e) { 
    isFileUnlocked = false; 
    } 

    if(isFileUnlocked){ 
    // Do stuff you need to do with a file that is NOT locked. 
    } else { 
    // Do stuff you need to do with a file that IS locked 
    }