What is the purpose of gradle's buildSrc folder?
configuration, gradle, structure
Solution
`buildSrc` is a separate build whose purpose is to build any tasks, plugins, or other classes which are intended to be used in build scripts of the main build, but don't have to be shared across builds.(*) It wouldn't be possible to build such classes as part of the main build, because they have to exist before the main build's build scripts can even be compiled/evaluated, and Gradle compiles/evaluates all build scripts before it does any work (configuration vs. execution phase).
Compared to putting all build code into build scripts, `buildSrc` gives you a way to develop build code more like regular code, as classes that you can test, import into your IDE, etc. It is one way to keep build scripts simple and DRY even for more complicated builds.
`buildSrc` is more often seen in multi-project builds simply because larger builds are more likely to implement their own custom tasks and plugins.
Over time, `buildSrc` will grow into a more general capability of executing multiple dependent builds in a single Gradle invocation.
(*) Sharing classes across builds is possible but more involved. In particular, you'll need to publish the classes to a repository, and consuming builds have to explicitly import them from there, similar to when sharing production libraries between builds.
Problem
In gradle, what is the purpose of using a `buildSrc` file as a top level, as opposed to just a typical java project layout (src/main/java)? If I have a layout of ``` src main java ``` or ``` buildSrc src main java ``` What would be the difference (or the reason for doing this)? Is it more useful in multi module projects? Even for a multi module project, couldn't I do something like ``` proj1 src proj2 src ``` And then just have a top level build.gradle (at the same level as `proj1` and `proj2`) that defines common settings across the projects?