Creating a custom FileSystem implementation in Java

Question

I read on oracle that it is possible to create a custom FileSystem, but I can't really find much documentation on creating one. Could anyone link me to somewhere I can learn more about custom FileSystems?

Where I read about this: http://docs.oracle.com/javase/7/docs/technotes/guides/io/fsp/filesystemprovider.html

The link you provided contains the information on how to implement custom file system. What else do you need? — Oleg Estekhin
– Oleg Estekhin, Commented Apr 9, 2014 at 14:50
How to actually create it. Maybe an example? I couldn't really find enough info to go on to actually create one. — Mr. Awellstein
– Mr. Awellstein, Commented Apr 9, 2014 at 14:52
I think OpenJDK contains the source of the Zip File System Provider somewhere, if you would like to look at an example. — Puce
– Puce, Commented Apr 9, 2014 at 14:54
The link you provided contains a reference to the ZipFileSystemProvider as an example of a custom file system provider. I think you should really read that document, especially if you yourself gave a link to it. — Oleg Estekhin
– Oleg Estekhin, Commented Apr 9, 2014 at 14:56
check under your jdk installation for demo/nio/zipfs/src.zip as stated in the link you provided. You can also find it here — bachr
– bachr, Commented Dec 19, 2014 at 14:09

btiernay · Accepted Answer · 2015-10-01 23:18:25Z

16

A (Real) Simple Example

A very simple Java FileSystem to use as an example is nodet/githubfs. There are only a few classes and it will give you the flavor of how to implement a basic file system. The primary classes are:

Note that this file system does not implement all operations (which is part of the reason it is good as a high level example).

Experiment!

To experiment with using a custom FileSystem without any coding, a handy project is puniverse/javafs. It allows you to mount it as a FUSE and interact with it from a terminal. Setup is quite easy:

import co.paralleluniverse.javafs.JavaFS;
...
// Need to mkdir /tmp/mnt first
JavaFS.mount(fileSystem, Paths.get("/tmp/mnt"));
Thread.sleep(Long.MAX_VALUE);

edited Oct 1, 2015 at 23:18

answered Oct 1, 2015 at 12:01

btiernay

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1 Comment

Román Over a year ago

Is this approach similar to AndrewFileSystem? I have a work in some months and can't really know where to start. Thanks in beforehand.

rboyer · Accepted Answer · 2014-04-13 21:52:03Z

9

Google opensourced a completely in-memory filesystem implementation called JimFS: https://github.com/google/jimfs

answered Apr 13, 2014 at 21:52

rboyer

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Comments

BhaskarG · Accepted Answer · 2018-07-21 14:52:25Z

I know this is an old question but many people still want the actual answer, which is not here. The problem is that the documentation by Oracle (Sun), listed by the OP is missing critical information. What adds to the confusion is that the "demo" referenced by the doc is packaged in a confusing way. There is a Demo.java source file and src.zip and a zipfs.jar. The Demo.java is NOT a FileSystemProvider. Its a custom FileSystem. For it to work you have to add the zipfs.jar to the "extensions" folder of your JRE/JDK, so that when the Demo.getZipFSProvider() method is called, it will find the custom FileSystemProvider which returns the custom FileSystem. If you look in the src.zip you will find the code for the provider. If the Java documentation had been properly written this question would not have come up. Its confusing. Even the readme file in the demo makes no mention of the provider. Sad.

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