多线程使用LockFIle，每个线程Lock一部分文件

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;

public class LockFiles {

    static final int   LENGTH = 1000000;
    static FileChannel fc ;

    public static void main(String[] args) throws Exception {

        File file = new File("D://in.txt");
        FileOutputStream fo = new FileOutputStream(file);//可使用OutputStream和RandomAccessFile，使用InputStream会抛出异常NonWritableChannelException 

        fc  = fo.getChannel();
        ByteBuffer out = ByteBuffer.allocate(LENGTH);

        for (int i = 0; i < LENGTH; i++)

            out.put((byte)( 'i'+i));

        new LockAndModify(out, 0, 0 + LENGTH / 4);

        new LockAndModify(out, LENGTH / 3, LENGTH / 3 + LENGTH / 4);

    }

 

    private static class LockAndModify extends Thread {

        private ByteBuffer buff;

        private int        start, end;

 

        LockAndModify(ByteBuffer mbb, int start, int end) {

            this.start = start;

            this.end = end;

            mbb.limit(end);

            mbb.position(start);

            buff = mbb.slice();

            start();

        }

        
        public void run() {

            try {
                FileLock fl = fc.lock(start, end, false);

                System.out.println("The Buffer Locked: " + start + " to " + end);


                while (buff.position() < buff.limit() - 1){
                   	buff.put((byte) (buff.get() + 1));
                   	}
                fl.release();

                System.out.println("The Buffer Released: " + start + " to " + end);

            } catch (IOException e) {

                throw new RuntimeException(e);

            }

        }

    }

}

运行结果如下：The Buffer Locked: 333333 to 583333
The Buffer Locked: 0 to 250000
The Buffer Released: 333333 to 583333
The Buffer Released: 0 to 250000
如果两个线程的锁定重叠就会抛出如下异常：Exception in thread "Thread-1" java.nio.channels.OverlappingFileLockException

评论

1 楼 hejianmingwshjmcj 2012-09-07  

不知道应用到什么场景