What is a safe way to create a Temp file in Java?
JavaTemporary FilesJava Problem Overview
I'm looking for a safe way to create a temp file in Java. By safe, I mean the following:
- Name should be unique, even under potential race conditions (e.g. another Thread calls the same func at the same time, or another process runs this code simultaneously)
- File should be private, even under potential race conditions (e.g. another user tries to chmod file at high rate)
- I can tell it to delete the file, without me having to do a generic delete, and risk deleting the wrong file
- Ideally, should ensure file is deleted, even if exception is thrown before I get the chance to
- File should default to a sane location (e.g. the JVM specified tmp dir, defaulting to the system temp dir)
Java Solutions
Solution 1 - Java
File tempFile = File.createTempFile("prefix-", "-suffix");
//File tempFile = File.createTempFile("MyAppName-", ".tmp");
tempFile.deleteOnExit();
Will create a file in the temp dir, like:
> prefix-6340763779352094442-suffix
Solution 2 - Java
Since Java 7 there is the new file API "NIO2" which contains new methods for creating temnp files and directories. See
e.g.
Path tempDir = Files.createTempDirectory("tempfiles");
or
Path tempFile = Files.createTempFile("tempfiles", ".tmp");
Security notice:
Important difference between File.createTempFile()
and Files.createTempFile
is also that the latter has more secure permission defaults.
> When no file attributes are specified, then the resulting file may
> have more restrictive access permissions to files created by the
> File.createTempFile(String,String,File)
method.