Question

我运行一个任务来每5秒写一次文件，java程序写入成功到test.txt 但是文件file.txt lastModified仍然是创建时间，而不是lastModified时间。我用strace来看看有什么不对。

strace shell：

strace -e msync -f -p 24036

Process 24036 attached with 19 threads - interrupt to quit
[pid 24054] msync(0x2aaaaf5e9000, 10000, MS_SYNC) = 0
[pid 24054] msync(0x2aaaaf5e9000, 10000, MS_SYNC) = 0
[pid 24054] msync(0x2aaaaf5e9000, 10000, MS_SYNC) = 0
[pid 24054] msync(0x2aaaaf5e9000, 10000, MS_SYNC) = 0
[pid 24054] msync(0x2aaaaf5e9000, 10000, MS_SYNC) = 0

java演示代码：

import java.io.File;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


public class Test2 {
    private static String file = "/home/fuyou/test/test.txt";

    public static void main(String[] args) {
        ExecutorService executorService = Executors.newCachedThreadPool();
        executorService.submit(new Runnable() {
            @Override
            public void run() {
                try {
                    write();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
}

public static void write() throws Exception {
    RandomAccessFile randomAccessFile = new RandomAccessFile(new File(file), "rwd");
    FileChannel fileChannel = randomAccessFile.getChannel();
    MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, 10000);
    int i=0;
    while (true) {
        if(++i>=126){
            i =1;
        }
        mappedByteBuffer.position(i);
        mappedByteBuffer.put((byte)i);
        System.out.println("write...");
        Thread.sleep(5000);
        mappedByteBuffer.force();

    }

}
}

当我在Mac OSX10.9中运行一些代码时，文件lastModified按预期每5秒更新一次，那么我的程序有什么问题？

操作系统是：

uname -a
Linux  2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

cat /etc/issue

Red Hat Enterprise Linux Server release 5.4 (Tikanga)
java version "1.6.0_23"

在Java中，如何使用MappedByteBuffer同步文件元数据

0 个答案: