[
https://issues.apache.org/jira/browse/MNGSITE-550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17907553#comment-17907553
]
ASF GitHub Bot commented on MNGSITE-550:
----------------------------------------
mthmulders commented on code in PR #598:
URL: https://github.com/apache/maven-site/pull/598#discussion_r1894580250
##########
content/markdown/whatsnewinmaven4.md:
##########
@@ -0,0 +1,466 @@
+# What's new in Maven 4?
+
+Maven is over 20 years old and is one of the most used build-tool in the Java
world.
+Since all the years one important rule was the highest backward-compatibility
as possible, especially with
+its [POM-schema with Model version 4.0.0][2], used for the build itself, but
also by consumers.
+This made Maven more than a tool, but a whole ecosystem with a lot of things
depended on the POM, esp. the Maven Central
+repository, other build tools and IDEs.
+But this stable schema comes at a price - the lack of flexibility.
+
+> "With the Maven build schema preserved in amber, we can’t evolve much: we’ll
stay forever with Maven 3 minor releases,
+> unable to implement improvements that we imagine will require seriously
updating the POM schema…"
+> — <cite>[Hervé Boutemy (in Javaadvent 2021)][1]</cite>
+
+Maven 4 will prepare to changes which are impossible nowadays, like a complete
new build schema.
+
+Another pain point of Maven 3 is a code base with a lot of deprecated,
convoluted, non performant and duplicated code
+which costs the volunteers who maintain Maven a lot of time.
+This not only means that the Maven codebases contains old Java code that can
be optimized nowadays, but also old
+dependencies and bad API design of its own APIs, especially for Maven plugins.
+Therefore, Maven 4 will also be a maintenance release.
+
+This article presents and explains major changes brought by Maven 4, grouped
into several topics.
+
+## POM-Changes
+
+### Build-POM and Consumer-POM
+
+As written in the introduction the Model version 4.0.0 is used not only for
the build, but also by consumers of the
+artifact.
+But several contents of the POM are only necessary for the build while others
like the dependencies are also needed by
+the consumer.
+Maven 4 will therefore differentiate between a "Build-POM" and a
"Consumer-POM".
+As names suggest the "Build-POM" will contain all information needed for to
build the artifact, e.g. used plugins and
+their configuration, while the "Consumer-POM", which is created during the
Maven build, will not contain those.
+This POM will only keep those which are really needed to use the artifact,
e.g. dependency information.
+
+**Note**: See below for a comparison of the content of both POMs.
+
+### Model version 4.1.0
+
+With now having two types of POM Maven 4 can already make additions to the
Build-POM as it will only be used by Maven (
+and of course IDEs).
+Therefore, with Maven 4 a new Model version 4.1.0 is introduced.
+This version introduces some new elements and attributes, while others got
marked as deprecated.
+To not break the ecosystem this version is only available for the Build-POM,
while the Consumer-POM will still use
+version 4.0.0.
+This means Maven will generate the Consumer-POM during the build.
+
+**Note**: Maven 4 will of course continue to build your model version 4.0.0
project!
+There is no need to update your POMs to 4.1.0 as long as you don't want to
make use of the new features.
+But as like every software update - it's suggested to update them to 4.1.0,
e.g. to avoid problems when deprecated
+things get removed in future updates.
+
+### Modules are now subprojects
+
+From the early days of Maven 1 till today, all build information is stored in
the POM, short for "Project Object Model".
+Together with build folders and other files the wording "Maven project" is
used.
+However, project containing multiple parts, e.g. an API and a client, each of
those parts was called "module" and listed
+in the `<modules>` section of the POM, leading to the terms of "multi-module
project".
+This wording introduced some inconsistency, especially as projects with any
`<modules>` section are often called "
+single-module".
+Since the introduction of the [Java Platform Module System][3] in Java 9 the
term "module" raised additional confusion.
+
+Maven 4 gets rid of this by naming "modules" as what they are - subprojects.
+Model version 4.1.0 contains a new element `<subprojects>`analogous to the now
deprecated, but still usable, element
+`<modules>`.
+
+**Note**: It's suggested to use the terms `multi-project setup` and
`single-project setup` to differentiate between a
+Maven project with or without subprojects.
+
+### New packaging type: bom
+
+Maven 4 introduces a dedicated packaging type to provide a [Bill of Material
BOM][4] called "bom" to differentiate more
+precisely between "parent POMs" and dependency managing BOMs.
+While the new type is only available with model Version 4.1.0 the final
outcome is a full Maven 3 compatible (model
+4.0.0) POM file!
+For an example see the link above or
+the [live coding by Maven maintainer Karl Heinz Marbaise at IntelliJ IDEA Conf
2004][5].
+
+**Note**: With Maven 4 it's also possible to exclude dependencies which are
declared by BOMs using the existing
+`<exclusions>` element.
+Also note that in Maven4 importing BOMs with classifier is now possible.
+Therefore, Maven team suggests that projects BOMs be generated as classified
artifacts (see Maven build "skinny" vs "
Review Comment:
The clarification helps me a lot, thanks @Bukama and @cstamas!
> Information about "What's new in Maven 4?"
> ------------------------------------------
>
> Key: MNGSITE-550
> URL: https://issues.apache.org/jira/browse/MNGSITE-550
> Project: Maven Project Web Site
> Issue Type: Improvement
> Reporter: Matthias Bünger
> Priority: Major
>
> A comprehensive article/list of the important changes in Maven 4 is needed.
> ----
>
> Issue based on the slack message / thread, started by [~cstamas]
> {quote}
> More and more times we get questions like "and what is new in Maven4?". We
> have no document that distills the relevant changes. Could someone try to
> collect that in cwiki or somewhere?
> {quote}
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
