The Minecraft API Is Now On Github
github.com
github.com
I added a Jenkins build job for it on BuildHive so anyone can download the bits if you want to play with the very limited banning API that they apparently have so far :) https://buildhive.cloudbees.com/job/swashbuck1r/job/Minecraf...
I hope they'll consider adding a build job for the official project.
Nonetheless the API is good news.
Bukkit made it really far with community extensibility via non-official APIs. Now they get to help define the official API based on real-word experience about what developers want to do with customizing Minecraft. They also recently announced that they are merging single player and multi-player, creating a single mod-able codebase. http://www.mojang.com/2012/07/minecraft-1-3-info-snapshot-w2...
Minecraft-API
|- src
|- main
|- java
|- net
|- minecraft
|- workbench
On my machine that means it would end up being: /home/ajf/Projects/2012/Minecraft/Minecraft-API/src/main/java/net/minecraft/workbench/
Who on earth thought deeply nested directories for packages was a good idea?
Java does not stop you from doing this:
Minecraft-API
|- srcI do this all the time using static inner classes.
|- main
|- java
Correction: As per the message below I guess I should say that it has nothing to do with Java, the ecosystem, framework he is using is forcing him to use that hierarchy.
Maven requires a standard directory layout. Maven chose that hierarchy, because:
1) Namespacing. With tens or hundreds of thousands of packages out there, there needs to be an unambiguous way to refer to them separately.
2) Multiple language support. Maven can do Java, Scala, Clojure, Groovy, and so on - in the same project, even. It can even do Javascript, which isn't a JVM language, in certain cases. For the JVM languages, if you want a multi-lamguage project, there has to be an easy way to interoperate (this is enabled by namespacing).
3) Separation of test code and program code. Don't ship tests with your binary package.
4) Separation of code from data.
5) Automation - of packaging, IDE support, etc. This has to do with all of the previous ones. You want to produce a JAR, but don't want to include the default log configuration. So you package the project up. It just happens. You want to edit the code in your IDE. So you add the project. All libraries are downloaded and on your classpath. Add a few lines to your config (as a per-system-user setting or per-project setting, take your pick). Java documentation and source code for those libraries is automatically downloaded. Eclipse hooks it up for you.
Suddenly, this:
src/main/java
src/main/scala
src/main/resources
src/test/java
src/test/scala
src/test/resources
...makes a lot more sense. It's hardly overengineering, but even then, the engineer isn't the one engineering the build system; these are details Maven takes care of.
[Aside: I am appalled and flabbergasted by the ignorance typically leveled at Java by people who don't understand it✝. It has real flaws, don't get me wrong, but making dependency resolution and installation ridiculously straightforward, multi-language builds dead simple, and unit testing a core feature - these are good things.]
Take a look at ant and compare it to maven and you'll see which one makes your life easier✝✝.
✝ I have worn many hats, and have experience with Python, Ruby, PHP, C, Java, and a little bit of Scala in real world contexts, among others. So I'm not a noob who hasn't experienced elegance or conciseness or performance. Java is actually an amazing language that many people don't give it credit for. Though the syntax can be pretty ugly even when the code is conceptually solid.
✝✝ Losing a bit of nuance here - ant gives you configuration. maven gives you convention. Ant is good for very custom; maven is good for straightforward processes.
Things like the Play! Framework can get away with it because the framework is basically an exoskeleton around the Java code rather than a traditional container.
It is true that more steps have to be done "manually," but the build is 10x more deterministic than Maven. For example, think about this:
With Maven I spend two months developing $APP on my machine. Maven does its magic dependency downloading at time t0. Then someone else starts hacking on $APP at time t1 on their machine, and as the first step, they do the magic dependency downloading and it breaks. Why does it break? Different configuration? Different OS? One of the 100 servers for the app's 100 dependencies broke? An incompatible change introduced in one of the 100 dependencies during an interval of t1-t0 = 2 months? Different version of one of the 100 dependencies?
At least Ant builds are deterministic. Maven builds depend on remote Internet resources remaining the same over time. Spoiler: They don't. Libraries are updated all the time. Often the changes are incompatible (sometimes intentionally, sometimes not). URL's become dead as businesses and organizations change their file structure, change CMS'es, change domain names, merge, go out of business.
With Maven, I'll admit that when things work, they're easier. But when they break, there's so much automagic going on -- including the contents of remote servers you don't control -- that it's tough to know where to begin finding the problem. Whereas with Ant, it's fairly easy to understand exactly what's going on, and you have a good chance of fixing it.
I'm sure most HN readers know exactly how frequently build systems of all stripes break, and how important it is to quickly troubleshoot build issues so you can get back to work that actually creates some sort of value :)
In practice, as far as I've seen, one should specify the exact versions of the library you're pulling. This is done explicitly in the name of build reproducibility. The "main" repositories should be preferred unless something really custom is needed - in which case, you should be running your own package repository with the libraries you need.
So I guess more tips for maven:
1) Prefer releases over snapshots of libraries whenever possible.
2) Consider running an artifact repository if you're working with a large enough team. It's simple enough that it'd speed you up nicely even if your entire project lives on one laptop, if you're comfortable with a few details of running it. This is strictly optional but will make certain team-based workflows smoother.
3) Always specify versions manually! Don't set it to use the latest automatically. Is this ever a good idea?
4) Try not to include too many third-party repositories if you can.
It's not hard to get Maven dependencies under control. The dependencies are also cached locally, so Maven builds should depend on the internet only the very first time their dependency is included, and thereafter, every time they are updated, only for the package that was updated. Maven is actually -very- good at repeatable builds by default.
Every time I've used it, it downloads hundreds of megabytes of who-knows-what from who-knows-where on the Internet. It's not like apt-get, which uses a central server where there's some level of QA to make sure all the versions of all the pieces work together.
Maven just shoves 100 different components from 100 different servers on your disk. If any one of those servers happens to be down, or moved, or the organization running it dies off, there goes your build.
I'll stick with Ant and manual dependency downloading, thanks. They're a pain in the arse, but at least you can keep the tarballs of the stuff you download around, and can have different library versions for different applications.
Its a little bit to wrap your head around to get started with maven. The first time I had to write a pom.xml file I almost burnt down my house. However SBT came along and fixed that problem. The only problem I have with maven now is that there is no way to tell it to make a single binary without a plugin.
Maven lets you keep different library versions around for different applications. This is actually a fundamental thing I've noticed everywhere I've personally seen it used: specify the versions. However you use Maven is evil. Your usage pattern needs to be improved.
FWIW, if I were listing "things to criticize Java for", I can't imagine that the package mechanism would be anywhere near the top 25, top 50, or even top 100. Unless you're routinely navigating around that structure using command line tools (which I suppose some Java developers do), I don't see the problem. Pretty much any modern IDE makes it nearly painless to navigate around the source code.
But yes, Java's packaging is mostly a good thing.
When I found this out, it changed my life.
You'll see this on lots of JVM-based projects.
I tip my hat to him for his commitment to "release early, release often."
Mods for Minecraft have been around almost as long as Minecraft has been. These mods took the form of patches to the decompiled .jar archives that the client and server code was distributed as.
It quickly became clear that different mods would often patch the same files, usually in contradictory ways, so applying different mods at the same time was near impossible.
Two projects sprang up to make the modder's life easier: hMod by hey0 [1] and the Minecraft Coders Pack (MCP) [2].
MCP was an attempt to translate decompiled obfuscated java code into something 'meaningful' that could be used to more easily write mods. Some of the people who would later go on to work on Bukkit were involved in this project. MCP also played a large role in keeping mods up to date as new versions were released.
Hey0's mod 'hmod' was the first successful server mod that provided an abstracted 'API' for developing plugins against. The community loved this idea, and an ecosystem of plugins sprung up extremely quickly around it. Server administrators were now able to install many different plugins, each of which would (almost certainly) work with each other at the same time.
Unfortunately, hey0 lost interest in the project, and the group that had started to maintain it felt they were often working against the code base, rather than with it. Hey0 was a relatively new programmer when he started the project (I think he was 14?) and while a lot was achieved there were a few architectural aspects that were extremely hard to change.
For better or worse (probably better in retrospect) the team that had started to maintain hmod broke off to a new project called Bukkit [3]. The four main team members at that point were EvilSeph, Dinnerbone, Grum and Tahg. This is the 'core' Bukkit team that was hired by Mojang a little while ago to work on Minecraft (and probably other things) full time.
I had started developing on hmod a few months before Bukkit started, and switched to it soon after. I eventually became one of the main contributors to that project, and still get involved from time to time.
Bukkit as a project aimed to learn from hmod, incorporating much of what was learnt from the mistakes in the original design. The project was still very young, and there was a lot of pressure on the project from the community. The pressure was primarily a result of hmod dying once the team that was supporting it moved on.
Every time a new Minecraft version was released, the server mods had to be updated. The new clients wouldn't work with an old server version, and there was no easy way to downgrade a client, so server administrators would have many angry users who could not connect to their modded server. The upgrade process was by far the most troublesome for a modding project, and was what the MCP project was most helpful in assisting with.
The source code would need to be decompiled, and then deobfuscated. Any changes by the mod would then need to be re-applied to the newly deobfuscated source, before repackaging everything for the server admins to install. One of the biggest problems with hmod was how incredibly hard and slow this process was. It would often take days if not weeks for this upgrade process to complete. When the team left hmod no one was left to rebuild it every time there was a new release, and so hmod died. It took a long time before anyone was able to revive that project [4]. Bukkit was designed first around making this process as easy as possible, and the results showed. A number of updates took less than a few hours from the time a new version was released by Mojang.
That being said, Bukkit had many issues. One that I was constantly working with was the number of classes implemented in the 'API' section of the code. We used two projects, Bukkit and CraftBukkit, to separate the plugins from the source code. Bukkit was what plugins linked against, and provided a stableish API that wouldn't break (too often). CraftBukkit implemented all the necessary hooks and behaviours in the server itself. Unfortunately, some classes were built into the API that made things quite difficult. We were locked into certain material behaviours, for example, because of the way they were implemented. Interestingly, one of the 'Coding standards' for the new API addresses this directly
Absolutely no already-implemented classes. Use interfaces, and have util classes created by a implementation-controlled Factory.
So I see it this way: Bukkit was created 'from fresh' to address some extremely difficult problems that made maintaining the existing solution (hmod) extremely time consuming and troublesome. As Bukkit matured it was able to deal with lots of issues, but some kept re-occurring. Integrating with client-side mods was a common problem that had no easy solution in the way Bukkit worked, for example. When the opportunity to create a supported, integrated plugin system presented itself, experience said that starting fresh was going to be the easiest way.
Something that might not be clear is that the actual Minecraft source code is (apparently - I have never seen it myself) very different to the decompiled and de-obfuscated version that CraftBukkit built on. To take advantage of being able to change the original source code much of what CraftBukkit does would need to be rewritten. Changing the API side of things (Bukkit) at the same time frees them to make better choices and learn from mistakes.
We will surely find out if that turns out to be the case, but for now I am quite excited to see what happens.
[1] http://www.ohloh.net/p/hmod - there is probably a better resource, but I can't find it
[2] http://mcp.ocean-labs.de/index.php/Main_Page
EDIT: grammar and such