this post was submitted on 12 Sep 2023
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Why are packages labled com.person.mypackage rather than just person.mypackage

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[–] fubo 49 points 1 year ago (1 children)

They used DNS domains as a namespace to keep one company's work from colliding with another.

https://en.wikipedia.org/wiki/Reverse_domain_name_notation

[–] [email protected] 24 points 1 year ago (1 children)

To expand on this, it’s the naming convention that Java defines.

Package names are written in all lower case to avoid conflict with the names of classes or interfaces.
Companies use their reversed Internet domain name to begin their package names—for example, com.example.mypackage for a package named mypackage created by a programmer at example.com.

https://docs.oracle.com/javase/tutorial/java/package/namingpkgs.html

[–] orclev 15 points 1 year ago (1 children)

Further it isn't always com, you'll often see net, org, and rarely even io show up as the base package. All that said with the introduction of modules and some of the other recent changes I'm not sure how much longer we're going to see the reversed DNS naming system stick around.

[–] qaz 11 points 1 year ago* (last edited 1 year ago) (1 children)

I’ve quite often seen people shoehorn their Github account into this format. com.github.username.projectname is quite a common sight for Flatpak packages. Reverse DNS naming assumes every package is created by a company while nowadays a large portion of popular packages were created by individuals.

[–] [email protected] 4 points 1 year ago (1 children)

It doesn't check for an actual DNS entry though, right? Would it be possible to do person.developer.app?

[–] orclev 13 points 1 year ago

Correct, there's no actual validation done. You can literally make the package anything you want, you don't even need to follow the convention if you don't want to, although it is of course considered best practice to do so. The entire reason it exists is just as a convenient way to namespace Java classes without worrying about collisions. I personally think using com.github.username.projectname is a perfectly fine way to use the system and is completely within the spirit of it. Likewise if you wanted to use person.developer.app you could, although that's a little weirder. You might be better off using something like dev.person.app, although you'd need to be careful you don't accidentally step on someones toes if someone actually has the registration for person.dev.

[–] [email protected] 7 points 1 year ago

I addition to the answers others have given, consider the large centralized package repositories for software development: npm, PyPI, crates.io, etc. If you frequently publish packages to these indexes, you often will find name collisions and are forced to come up with clever names. In the case of PyPI specifically, it is even worse because while your pip package might be uniquely named, the actual importable python package may not be, and you end up where two pip packages clobber each other. Java's system is verbose but it is simple and solved this problem decades ago.