java set file permissions to 777 while creating a

问题:

Possible Duplicate:
How can I set the umask from within java?

How do you set file permissions to 777(or any other arbitrary permission) while creating a file object in java?

回答1:

If you set the umask(2) to 0 before starting the JVM, all files and directories created will be created with full permissions for everyone. This is probably a bad idea.

You can use the File.setReadable(), File.setWritable APIs to fiddle with the mode bits after the file has been created. That's often good enough, if you're granting permissions; if you're trying to remove permissions from other users, then your permissions should probably be set very restrictively from the start. (umask(0777) before launching the JVM, then add permissions exactly where you want them.)

回答2:

3 methods are available:

setReadalble(boolean boolean)
setWritable(boolean,boolean)
setExecutable(boolean,boolean)

This will set the file to "0777"

String path = "SOME/PATH";

final File file = new File(path);
file.setReadable(true, false);
file.setExecutable(true, false);
file.setWritable(true, false);

回答3:

Java SE 7 has java.nio.file.attribute.PosixFileAttributes which gives you fine grained control over read, write, and execute permissions for owner, group, and others.

import java.nio.file.*;
import java.nio.file.attribute.*;
import java.util.Set;

public class Test {
    public static void main(String[] args) throws Exception {
        Path path = Paths.get("/tmp/test-file.txt");
        if (!Files.exists(path)) Files.createFile(path);
        Set<PosixFilePermission> perms = Files.readAttributes(path,PosixFileAttributes.class).permissions();

        System.out.format("Permissions before: %s%n",  PosixFilePermissions.toString(perms));

        perms.add(PosixFilePermission.OWNER_WRITE);
        perms.add(PosixFilePermission.OWNER_READ);
        perms.add(PosixFilePermission.OWNER_EXECUTE);
        perms.add(PosixFilePermission.GROUP_WRITE);
        perms.add(PosixFilePermission.GROUP_READ);
        perms.add(PosixFilePermission.GROUP_EXECUTE);
        perms.add(PosixFilePermission.OTHERS_WRITE);
        perms.add(PosixFilePermission.OTHERS_READ);
        perms.add(PosixFilePermission.OTHERS_EXECUTE);
        Files.setPosixFilePermissions(path, perms);

        System.out.format("Permissions after:  %s%n",  PosixFilePermissions.toString(perms));
    }
}

Which can then be used like:

$ rm -f /tmp/test-file.txt && javac Test.java && java Test
Permissions before: rw-r--r--
Permissions after:  rwxrwxrwx