Many coworkers I've worked with have called it complicated and then I find out they really haven't learned the (very simple) lifecycle and how build behavior gets attached, etc. This is all very simple but it is something to learn.

I don't know why this happens. I think programmers are so used to imperative (ant/Grunt/etc/etc) programming/building that it becomes confusing for them when they encounter a declarative system. And their brain revolts. Because they are like how do I just do a thing (i.e., copy some file somewhere, call a "build" method, etc, etc.)!? Instead of realizing the value of the declarative + idiomatic Tao and learning it...they say no, no gimme gimme let meee do it. Much like my two year old. And then I'm left fighting non-reproducible builds and getting their projects going in my IDE like it's somehow 2005 again. But Maven is great, declarative systems -- especially declarative build systems are the optimal way to do builds (in most cases).

For example, if you have a multi-pom project with a parent pom (not unusual in a medium-sized codebase, never mind large), and you have unit tests in your child poms, they'll get executed with dependencies resolved locally for that child pom, and not with the global dependency resolution that satisfies all constraints that need satisfying at the parent level.

The upshot is that you easily end up running tests using different versions of dependencies than what you deploy with, misleading you into thinking things are working, and can end up with hilarious NoSuchMethodError at runtime.

The "solution" is to pin your versions using dependencyManagement, but that's no real solution at all, not least because it's neither automatic (though dependency convergance using Maven Enforcer helps, and I've developed some scripts that help further) nor is there an easy route forward when you want to bump versions safely.

As it should, otherwise you'd get the even more hilarious situation where your tests pass when you run the single-module build but fail when you run the multi-module build.

> The "solution" is to pin your versions using dependencyManagement, but that's no real solution at all, not least because it's neither automatic (though dependency convergance using Maven Enforcer helps, and I've developed some scripts that help further) nor is there an easy route forward when you want to bump versions safely.

This is not a maven issue, it's a combination of Java's flat classpath and the reality of diamond dependencies on versioned libraries in any system. We could allow multiple versions of a transitive dependency on the classpath but then you get Rust's hilarious "expected Foo but was Foo" type errors. Java 9 modularisation should reduce the problem by allowing modules to have explicitly private dependencies, but the problem exists everywhere.

This isn't true; there are better solutions already existing. E.g. Ruby with the Gemfile.lock approach. I'd like to be able to do a two-step: do a global analysis of dependencies and pin the common versions for diamond situations, but not need to maintain or calculate those pinned versions manually. And I still get to use the pinned versions from the global resolution for executing tests etc. on submodules.

As it is, I've had to write a bunch of tools to rewrite the dependencyManagement as and when required. The main app I work on is linked into the Hadoop ecosystem, and that dependency set ends up being quite large.

Another issue with Maven is rebranding: when the groupId of an artifact changes, but the package and class names don't; see e.g. asm / asm vs org.ow2.asm / asm, or the whole codehaus debacle.

I have spent more than two weeks of my life updating, maintaining, fixing, researching and tooling Maven pom files, and it was almost all around deficiencies in dependency management.

Let's not get started on trying to get builds to work reliably offline, caching maven repositories, etc.

I dislike this for the same reason as before: I find it really valuable that building a single module on its own behaves the exact same way as building that module as part of a multi-module project. If you want to ensure that the tests run against the same version as in the final product, I do that by making eviction an error.

> Another issue with Maven is rebranding: when the groupId of an artifact changes, but the package and class names don't; see e.g. asm / asm vs org.ow2.asm / asm, or the whole codehaus debacle.

Maven has better handling of this than most; it can at least warn/error when this has happened, and if you're using the shade plugin or similar it will warn or error when two jars contain the same classes. Yes it's a problem, but it's much more of a problem in other ecosystems.

> As it is, I've had to write a bunch of tools to rewrite the dependencyManagement as and when required. The main app I work on is linked into the Hadoop ecosystem, and that dependency set ends up being quite large.

There are standardized plugins for the common use cases e.g. "mvn versions:use-latest-releases". Most things that can be automated are. But since most of the library ecosystem predates version ranges and semVer, there simply isn't an automated way to know when using a newer version of a transitive dependency is safe or not.

Because, after all is said and done, programming is about having your computer "do" something - whether it be to write some bytes to the disk or to send some bytes to the network.

It's just that sometimes there's an advantage to use an abstraction - such as say "SELECT * FROM TABLE WHERE ROW_ID =14" is an abstraction over something like "for (int i =0;i<table.size();i++) if(table.row[i].elem[1] == 14) ... ", but often you don't need such a complicated abstraction, you just "need something done" before (or after) building. Whether it be that you want to download an HTML file to package, or to move the resulting file to a certain directory, or to clean a certain directory, your build language shouldn't be that arcane that you have to create a "build.sh" to get things done.

— Maven is simple, not arcane. I’ve produced countless “custom” builds with wild variations of need and never has Maven let me down. In some sense this is easy to prove (see maven-antrun-plugin); however, Maven’s core plugin/idioms supports 90+% of use cases I’ve seen over many many “weird” build requirements. To your example, “copying files” is fundamental; however you have to learn the idiomatic way to do it if you want to reap the benefits. Otherwise, just call out to maven-antrun- or similar. But then you’re chasing your tail.

The issue with convention over configuration is that you don't see how things should happen, because they're hidden behind the convention.

For example, what are the steps behind your Android build? Can you tell me exactly what steps gradle takes when you run gradlew assembleDebug?

So if for whatever reason you need to modify something, you're completely on your own.

$ gradlew -m assembleDebug

Learn the tools you use..

Not always. Often, particularly in scientific computing, you just want to ... compute ... a result. I mean sure, the computer needs to display the result to you, but the computation isn't about displaying it, it's about computing it. Just like adding up a bunch of numbers on a calculator isn't about getting the calculator to "do" anything.

> often you don't need such a complicated abstraction, you just "need something done" before (or after) building.

Abstractions should be simpler than the thing they abstract over, that's their whole point. Treating my computer's memory as a flat array of numbers is simpler than thinking about how much current is flowing through each RAM wire. "Compile all source files" is simpler than "execute javac Foo.java, then execute javac Bar.java, then..."

> Whether it be that you want to download an HTML file to package, or to move the resulting file to a certain directory, or to clean a certain directory, your build language shouldn't be that arcane that you have to create a "build.sh" to get things done.

You shouldn't need a build.sh, agreed, but nor should you need particular things to happen to particular directories. Maven has great support for things like "package my documentation in the standard way". It's only when people try to fight it about the low-level details that they really shouldn't be caring about that they run into trouble.

Building is a simple concept: dependency DAG + inputs -> artifacts. The "->" here can involve arbitrary intermediate artifacts and steps.

Maven ignores this fundamental concept of building. Rather than treat interim dependencies as part of the DAG, there's a hard-coded recipe of lifecycle steps.

This is why I personally cringe at maven - it has nothing to do with the fact that it's declarative (virtually every build system is largely declarative). It has everything to do with hard-coding one particular set of build steps into a supposedly general build tool.

With Maven, if you follow Maven's way of doing things, everything just works. But, if you need to do something different, or have some rare use case Maven's designers weren't focused on, you start struggling a lot to get Maven to do what you want.

Gradle is a lot more flexible and if you have some uncommon requirement you are far more likely to successfully implement it using Gradle than using Maven.

You'll be fine as long as you realise the Maven-ey way of doing the thing is to write your own plugin.

But most of the time people just want their build to do something different for no real reason, IME.

A short while later I was wondering why I'd never tried that before: Maven plugins are really quite simple to write.