Java comes with some handy tools to manipulate file permissions. Though Java File class has the ability to set the file permissions but it is not so versatile. The biggest drawback of Java’s file permission is that you can’t set the different file permissions for group and other users. That is you can divide the file permissions into two sets of users, owner and all other users.
For example you can not set different permissions for a file for different users and groups.
But Java 7 introduced PosixFilePermission (part of java.nio.file package) which allows us to set different permissions for different users and owners and groups. In this tutorial we shall see both type of examples before Java 7 and Java 7 file permissions.
Java File Permission Example
import java.io.File;
public class SetFilePermissionInJava
{
private static String MY_FILE = "/home/hduser/test/test.sh";
public static void main(String args[])
{
File file = new File(MY_FILE);
//Check if the files Exists
if(file.exists())
{
//Show the Present Permissions on the file
System.out.println("Is Readable: " + file.canRead());
System.out.println("Is Executable: " + file.canExecute());
System.out.println("Is Writable: " + file.canRead());
}
//Change the file permissions
file.setExecutable(true);
file.setReadable(false);
file.setWritable(false);
System.out.println("-----------New Permissions---------------");
System.out.println("Is Readable: " + file.canRead());
System.out.println("Is Executable: " + file.canExecute());
System.out.println("Is Writable: " + file.canRead());
}
}
Output
Is Readable: true Is Executable: false Is Writable: true -----------New Permissions--------------- Is Readable: false Is Executable: true Is Writable: false
The above example is not capable of setting different file permissions to different users or groups.
Now lets see Java 7 example of setting file permission which can set different permissions for users and groups.
Java 7 File Permission Example
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.util.HashSet;
import java.util.Set;
public class SetFilePermissionInJava7
{
private static String MY_FILE = "/home/hduser/test/test.sh";
public static void main(String args[])
{
//Lets use PosixFilePermission to set file permissions
Set<PosixFilePermission> filePerms = new HashSet<PosixFilePermission>();
//Owner File permission
filePerms.add(PosixFilePermission.OWNER_READ);
filePerms.add(PosixFilePermission.OWNER_WRITE);
filePerms.add(PosixFilePermission.OWNER_EXECUTE);
//For Group File Permissions (Only Read and Write for groups)
filePerms.add(PosixFilePermission.GROUP_READ);
filePerms.add(PosixFilePermission.GROUP_WRITE);
//For Others File permissions (Only read permission for others)
filePerms.add(PosixFilePermission.OTHERS_READ);
System.out.println("Done!!!");
try
{
Files.setPosixFilePermissions(Paths.get(MY_FILE), filePerms);
}
catch (IOException e)
{
System.out.println("Unable to change file permissions :" + e.getMessage());
}
}
}
You can refer above example codes to manipulate file permissions in your application as well. Hope this tutorial was helpful for you.
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