Java以独占的方式写文件的几种方法
来源:jxqlovejava
// 方案1:利用RandomAccessFile的文件操作选项s,s即表示同步锁方式写 RandomAccessFile file = new RandomAccessFile(file, "rws"); // 方案2:利用FileChannel的文件锁 File file = new File("test.txt"); FileInputStream fis = new FileInputStream(file); FileChannel channel = fis.getChannel(); FileLock fileLock = null; while(true) { fileLock = channel.tryLock(0, Long.MAX_VALUE, false); // true表示是共享锁,false则是独享锁定 if(fileLock!=null) break; else // 有其他线程占据锁 sleep(1000); } // 方案3:先将要写的内容写入一个临时文件,然后再将临时文件改名(Hack方案,利用了缓冲+原子操作的原理) public class MyFile { private String fileName; public MyFile(String fileName) { this.fileName = fileName; } public synchronized void writeData(String data) throws IOException { String tmpFileName = UUID.randomUUID().toString()+".tmp"; File tmpFile = new File(tmpFileName); FileWriter fw = new FileWriter(tmpFile); fw.write(data); fw.flush(); fw.close(); // now rename temp file to desired name, this operation is atomic operation under most os if(!tmpFile.renameTo(fileName) { // we may want to retry if move fails throw new IOException("Move failed"); } } } // 方案4:根据文件路径封装文件,并且用synchronized控制写文件 public class MyFile { private String fileName; public MyFile(String fileName) { this.fileName = fileName; } public synchronized void writeData(String data) throws IOException { FileWriter fw = new FileWriter(fileName); fw.write(data); fw.flush(); fw.close(); } } // 方案5:我自己想出来的一个方案,不太精确。通过切换设置读写权限控制,模拟设置一个可写标记量(蜕变成操作系统中的读写问题....) public class MyFile { private boolean canWrite = false; private String fileName; public MyFile(String fileName) { this.fileName = fileName; } public void writeData(String data) { while(!canWrite) { try { Thread.sleep(100); } catch(InteruptedException ie) { // } // 可以设置一个超时写时间 } canWrite = false; // Now write file } }