How to configure root for temp dirs in Java

Question

We run code which does the standard for creating a temp directory:

import java.nio.file.Files;

And then:

tmp = Files.createTempDirectory("ourprefix-");

This, effectively, creates the directories under /tmp/ so that we get things like /tmp/ourprefix-1234 or similar.

Unfortunately, this base directory /tmp/ seems to be fixed and since on our build server lots of things tend to put their temp stuff there and because the partition the /tmp/ is on is rather small, this is a problem.

Is there a way to configure this facility from the outside (i. e. without changing the code)? I would have guessed that /tmp/ is a default and can be overridden by setting a special environment variable or (more Javaish) passing a special property to the compiler (e. g. -Djava.tmp.root=/path/to/my/larger/partition/tmp).

I tried using java.io.tmpdir but setting this did not have any effect; it seems to be the default in case nothing is given to createTempDirectory() but in our case the code passes a prefix.

Any idea how to achieve what I want without changing the source code?

EDIT

After some investigation I found that this works just fine:

import java.nio.file.Path;
import java.nio.file.Files;
import java.io.IOException;

public class TestTempDir {
    public static void main(String[] args) throws IOException {
        System.out.println(System.getProperty("java.io.tmpdir"));
        Path path = Files.createTempDirectory("myprefix-");
        System.out.println(path.toFile().getAbsolutePath());
    }
}

Compile with javac TestTempDir.java, prepare with mkdir tmp and run with java -Djava.io.tmpdir=pwd/tmp TestTempDir this just works as expected:

/my/work/path/tmp
/my/work/path/tmp/myprefix-1525078348397347983

My issue rather seems to be one with Jenkins and its Maven plugin which does not pass the set properties along to the test cases :-/

Answer 1

if you pass the java.io.tmpdir property as a custom JVM property as you run the JVM, it should work.
Something like that :

java -Djava.io.tmpdir=myPath myClass

I tested and it works :

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

public class TestTempDir {

    public static void main(String[] args) throws IOException {
        System.out.println(System.getProperty("java.io.tmpdir"));
        Path dir = Files.createTempDirectory("helloDir");
        System.out.println(dir.toString());
    }
}

$ java -Djava.io.tmpdir=D:\temp TestTempDir

D:\temp

D:\temp\helloDir5660384505531934395