How to modify the permissions of Java files and folders
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Use the File class
This is the most common method in the past, but it has some drawbacks in LINUX or UNIX systems, where it is not so easy to display a specified permission of 440770.
File dirFile = new File (dirPath); dirFile.setReadable (true, false); dirFile.setExecutable (true, false); dirFile.setWritable (true, false)
So we usually use some workaround to modify folder permissions. I need to set the permissions to 770 on LINUX.
Runtime runtime = getRuntime (); String command = "chmod 770" + dirPath;try {Process process = runtime.exec (command); process.waitFor (); int existValue = process.exitValue (); if (existValue! = 0) {logger.log (Level.SEVERE, "Change file permission failed.");} catch (Exception e) {logger.log (Level.SEVERE, "Command execute failed.", e);}
There is a problem with this approach. When dirPath contains spaces or semicolons, it not only has an impact on functionality, but also has a hidden danger to security.
Case 1: dirPath = / home/an aa.txt
The command executed in the LINUX system is chmod 770 / home/an aa.txt, and the system will think that the file permissions of modify / home/an and aa.txt are 770. the modification of file permissions failed.
Case 2: when dirPath = / home/aaa.txt;rm test.txt
At this point, two instructions are executed on the LINUX system:
Chmod 770 / home/omc/aaa.txtrm test.txt
At this point, there will be security risks.
NIO mode
Private void changeFolderPermission (File dirFile) throws IOException {Set perms = new HashSet (); perms.add (PosixFilePermission.OWNER_READ); perms.add (PosixFilePermission.OWNER_WRITE); perms.add (PosixFilePermission.OWNER_EXECUTE); perms.add (PosixFilePermission.GROUP_READ); perms.add (PosixFilePermission.GROUP_WRITE); perms.add (PosixFilePermission.GROUP_EXECUTE); try {Path path = Paths.get (dirFile.getAbsolutePath ()); Files.setPosixFilePermissions (path, perms) } catch (Exception e) {logger.log (Level.SEVERE, "Change folder" + dirFile.getAbsolutePath () + "permission failed.", e);}}
From the API query, we know that this approach of NIO natively supports LINUX and UNIX low-level systems, but the test found that there seems to be no effect under the Windows system without distinguishing between the file owner and others, which is consistent with the practical File. From the underlying code, I found that the File class is still used.
In addition, UnsupportedOperationException IOException SecurityException may be thrown
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