Publish Jackson 3 module under new groupId org.msgpack.jackson3

Restructure the module layout per PR review feedback (JLBP-6): instead of
renaming the Jackson 2 artifact to jackson2-dataformat-msgpack and giving
Jackson 3 the unqualified jackson-dataformat-msgpack artifactId, rename the
Maven coordinates and the Java package together:

- Jackson 2 (msgpack-jackson): keeps org.msgpack:jackson-dataformat-msgpack
  and the org.msgpack.jackson.dataformat package, exactly as 0.9.x. Existing
  users need no changes. Maintenance mode: Jackson 2.x bumps and bug fixes only.
- Jackson 3 (msgpack-jackson3): published as
  org.msgpack.jackson3:jackson-dataformat-msgpack with the
  org.msgpack.jackson3.dataformat package, mirroring Jackson's own 2->3
  groupId rename (com.fasterxml.jackson.dataformat -> tools.jackson.dataformat).

Because the two artifacts share the same fully-qualified class names in
neither direction, they can coexist on one classpath, and dependency
resolution can never silently replace the Jackson 2 classes with Jackson 3
ones (or vice versa). The 1.0.0 version bump is no longer needed.

Both sbt subprojects now share the module name jackson-dataformat-msgpack,
so the Jackson 3 project overrides outputPath to keep sbt 2 build output
directories from overlapping.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C4Sp7Q2urgnYfuNXK2fVFm

Author: xerial

.github/workflows/CI.yml

@@ -28,7 +28,7 @@ jobs:
               - 'project/build.properties'
               - 'msgpack-core/**'
               - 'msgpack-jackson/**'
-              - 'msgpack-jackson2/**'
+              - 'msgpack-jackson3/**'
             docs:
               - '**.md'
               - '**.txt'
@@ -83,10 +83,10 @@ jobs:
         env:
           TEST_JAVA_HOME: ${{ steps.target-jdk.outputs.path }}
         run: |
-          # msgpack-jackson (Jackson 3) requires JDK 17+; older lanes test the
+          # msgpack-jackson3 (Jackson 3) requires JDK 17+; older lanes test the
           # Java 8 compatible modules only
           if [[ ${{ matrix.java }} -lt 17 ]]; then
-            ./sbt msgpack-core/test msgpack-jackson2/test
+            ./sbt msgpack-core/test msgpack-jackson/test
           else
             ./sbt test
           fi
@@ -95,7 +95,7 @@ jobs:
           TEST_JAVA_HOME: ${{ steps.target-jdk.outputs.path }}
         run: |
           if [[ ${{ matrix.java }} -lt 17 ]]; then
-            ./sbt msgpack-core/test msgpack-jackson2/test -J-Dmsgpack.universal-buffer=true
+            ./sbt msgpack-core/test msgpack-jackson/test -J-Dmsgpack.universal-buffer=true
           else
             ./sbt test -J-Dmsgpack.universal-buffer=true
           fi

.github/workflows/release.yml

@@ -38,17 +38,17 @@ jobs:
           PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
           TEST_JAVA_HOME: ${{ steps.jdk8.outputs.path }}
         run: |
-          ./sbt msgpack-core/publishSigned msgpack-jackson2/publishSigned
-      # msgpack-jackson (Jackson 3) requires JDK 17+
+          ./sbt msgpack-core/publishSigned msgpack-jackson/publishSigned
+      # msgpack-jackson3 (Jackson 3) requires JDK 17+
       - uses: actions/setup-java@v5
         with:
           java-version: 17
           distribution: temurin
-      - name: Build bundle for msgpack-jackson (Jackson 3)
+      - name: Build bundle for msgpack-jackson3 (Jackson 3)
         env:
           PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
         run: |
-          ./sbt msgpack-jackson/publishSigned
+          ./sbt msgpack-jackson3/publishSigned
       - name: Release to Sonatype
         env:
           SONATYPE_USERNAME: '${{ secrets.SONATYPE_USERNAME }}'

CLAUDE.md

@@ -6,8 +6,8 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 MessagePack-Java is a binary serialization library that provides a fast and compact alternative to JSON. The project consists of two main modules:
 - **msgpack-core**: Standalone MessagePack implementation with no external dependencies
-- **msgpack-jackson**: Jackson 3.x integration for object mapping capabilities (artifact `jackson-dataformat-msgpack`, Java 17+)
-- **msgpack-jackson2**: Jackson 2.x integration in maintenance mode (artifact `jackson2-dataformat-msgpack`, Java 8+)
+- **msgpack-jackson**: Jackson 2.x integration in maintenance mode (`org.msgpack:jackson-dataformat-msgpack`, Java 8+)
+- **msgpack-jackson3**: Jackson 3.x integration for object mapping capabilities (`org.msgpack.jackson3:jackson-dataformat-msgpack`, Java 17+)
 
 ## Essential Development Commands
 
@@ -50,8 +50,8 @@ The main entry point is the `MessagePack` factory class which creates:
 
 Key locations:
 - Core interfaces: `msgpack-core/src/main/java/org/msgpack/core/`
-- Jackson 3 integration: `msgpack-jackson/src/main/java/org/msgpack/jackson3/dataformat/`
-- Jackson 2 integration: `msgpack-jackson2/src/main/java/org/msgpack/jackson/dataformat/`
+- Jackson 2 integration: `msgpack-jackson/src/main/java/org/msgpack/jackson/dataformat/`
+- Jackson 3 integration: `msgpack-jackson3/src/main/java/org/msgpack/jackson3/dataformat/`
 
 ### Buffer Management System
 MessagePack uses an efficient buffer abstraction layer:
@@ -70,8 +70,8 @@ The msgpack-jackson module provides:
 ### Testing Structure
 - **msgpack-core tests**: Written in Scala (always use the latest Scala 3 version) using AirSpec framework
   - Location: `msgpack-core/src/test/scala/`
-- **msgpack-jackson / msgpack-jackson2 tests**: Written in Java using JUnit
-  - Location: `msgpack-jackson/src/test/java/`, `msgpack-jackson2/src/test/java/`
+- **msgpack-jackson / msgpack-jackson3 tests**: Written in Java using JUnit
+  - Location: `msgpack-jackson/src/test/java/`, `msgpack-jackson3/src/test/java/`
 
 ## Important JVM Options
 

README.md

@@ -57,12 +57,12 @@ msgpack-java supports serialization and deserialization of Java objects through
 
 Two artifacts are published depending on which Jackson major version your project uses:
 
-| Jackson version | Artifact | Requirements |
-| --- | --- | --- |
-| Jackson 3.x | [`jackson-dataformat-msgpack`](https://github.com/msgpack/msgpack-java/blob/main/msgpack-jackson/README.md) (1.x) | Java 17+ |
-| Jackson 2.x | [`jackson2-dataformat-msgpack`](https://github.com/msgpack/msgpack-java/blob/main/msgpack-jackson2/README.md) (maintenance mode) | Java 8+ |
+| Jackson version | groupId | artifactId | Java package | Requirements |
+| --- | --- | --- | --- | --- |
+| Jackson 3.x | `org.msgpack.jackson3` | [`jackson-dataformat-msgpack`](https://github.com/msgpack/msgpack-java/blob/main/msgpack-jackson3/README.md) | `org.msgpack.jackson3.dataformat` | Java 17+ |
+| Jackson 2.x | `org.msgpack` | [`jackson-dataformat-msgpack`](https://github.com/msgpack/msgpack-java/blob/main/msgpack-jackson/README.md) (maintenance mode) | `org.msgpack.jackson.dataformat` | Java 8+ |
 
-Since msgpack-java 1.0.0, `jackson-dataformat-msgpack` targets Jackson 3.x. If your project still depends on Jackson 2.x, either stay on `jackson-dataformat-msgpack` 0.9.x or switch to `jackson2-dataformat-msgpack` to keep receiving msgpack-core updates (only the artifactId changes; the Java package is the same). See each module's README for install instructions and usage details.
+The Jackson 2.x artifact keeps the same Maven coordinates and Java package as before, so existing users need no changes. The Jackson 3.x support is published under a new groupId (`org.msgpack.jackson3`) with a new Java package, following the same convention as Jackson itself (`com.fasterxml.jackson.dataformat` → `tools.jackson.dataformat`); renaming the Maven coordinates and the Java package together allows both artifacts to coexist on the same classpath for incremental migration. See each module's README for install instructions and usage details.
 
 - [Release Notes](https://github.com/msgpack/msgpack-java/blob/develop/RELEASE_NOTES.md)
 
@@ -153,6 +153,6 @@ If some sporadic error happens (e.g., Sonatype timeout), rerun `sonaRelease` aga
 
 ```
 msgpack-core                 # Contains packer/unpacker implementation that never uses third-party libraries
-msgpack-jackson              # jackson-dataformat-msgpack: Jackson 3.x integration (Java 17+)
-msgpack-jackson2             # jackson2-dataformat-msgpack: Jackson 2.x integration (maintenance mode)
+msgpack-jackson              # org.msgpack:jackson-dataformat-msgpack: Jackson 2.x integration (maintenance mode)
+msgpack-jackson3             # org.msgpack.jackson3:jackson-dataformat-msgpack: Jackson 3.x integration (Java 17+)
 ```

build.sbt

@@ -125,7 +125,10 @@ val isJava17Plus: Boolean = {
   // getOrElse(false): non-numeric versions (e.g. early-access "17-ea") fail safe
   // by not compiling the Jackson 3 module (msgpack-jackson) rather than making an
   // optimistic guess.
-  if (v.startsWith("1.")) false else scala.util.Try(v.toInt >= 17).getOrElse(false)
+  if (v.startsWith("1."))
+    false
+  else
+    scala.util.Try(v.toInt >= 17).getOrElse(false)
 }
 
 lazy val root = Project(id = "msgpack-java", base = file("."))
@@ -137,8 +140,12 @@ lazy val root = Project(id = "msgpack-java", base = file("."))
     publishLocal    := {}
   )
   .aggregate(
-    Seq[ProjectReference](msgpackCore, msgpackJackson2) ++
-      (if (isJava17Plus) Seq[ProjectReference](msgpackJackson) else Nil): _*
+    Seq[ProjectReference](msgpackCore, msgpackJackson) ++ (
+      if (isJava17Plus)
+        Seq[ProjectReference](msgpackJackson3)
+      else
+        Nil
+    ): _*
   )
 
 lazy val msgpackCore = Project(id = "msgpack-core", base = file("msgpack-core"))
@@ -182,49 +189,56 @@ lazy val msgpackCore = Project(id = "msgpack-core", base = file("msgpack-core"))
       )
   )
 
-// Maintenance-mode module for Jackson 2.x users: Jackson 2.x dependency bumps and
-// bug fixes only. To be dropped in a future major release when Jackson 2 usage fades.
-lazy val msgpackJackson2 = Project(id = "msgpack-jackson2", base = file("msgpack-jackson2"))
+// Jackson 2.x module. Keeps the same Maven coordinates (org.msgpack:jackson-dataformat-msgpack)
+// and Java package as the 0.9.x line, so existing Jackson 2.x users need no changes.
+// Maintenance mode: Jackson 2.x dependency bumps and bug fixes only.
+lazy val msgpackJackson = Project(id = "msgpack-jackson", base = file("msgpack-jackson"))
   .enablePlugins(SbtOsgi)
   .settings(
     buildSettings,
-    name                        := "jackson2-dataformat-msgpack",
+    name                        := "jackson-dataformat-msgpack",
     description                 := "Jackson 2.x extension that adds support for MessagePack",
-    OsgiKeys.bundleSymbolicName := "org.msgpack.msgpack-jackson2",
+    OsgiKeys.bundleSymbolicName := "org.msgpack.msgpack-jackson",
     OsgiKeys.exportPackage      := Seq("org.msgpack.jackson", "org.msgpack.jackson.dataformat"),
     libraryDependencies ++=
       Seq(
         "com.fasterxml.jackson.core" % "jackson-databind" % "2.22.1",
         junitJupiter,
         junitVintage,
         "com.github.sbt.junit" % "jupiter-interface" % JupiterKeys.jupiterVersion.value % "test",
-        "org.apache.commons" % "commons-math3" % "3.6.1" % "test"
+        "org.apache.commons"   % "commons-math3"     % "3.6.1"                          % "test"
       ),
     testOptions += Tests.Argument(TestFrameworks.JUnit, "-v")
   )
   .dependsOn(msgpackCore)
 
-lazy val msgpackJackson = Project(id = "msgpack-jackson", base = file("msgpack-jackson"))
+// Jackson 3.x module. Published under a new groupId (org.msgpack.jackson3) with a new
+// Java package (org.msgpack.jackson3.dataformat), following JLBP-6: the Maven coordinates
+// and the Java package are renamed together, so this artifact can coexist on the same
+// classpath with the Jackson 2.x artifact (org.msgpack:jackson-dataformat-msgpack).
+lazy val msgpackJackson3 = Project(id = "msgpack-jackson3", base = file("msgpack-jackson3"))
   .enablePlugins(SbtOsgi, JmhPlugin)
   .settings(
     buildSettings,
-    name                        := "jackson-dataformat-msgpack",
+    organization := "org.msgpack.jackson3",
+    name         := "jackson-dataformat-msgpack",
+    // sbt derives build output paths from moduleName, which would collide with the
+    // Jackson 2 module publishing the same artifactId; use the project id instead
+    outputPath                  := s"${platform.value}/u/msgpack-jackson3",
     description                 := "Jackson 3.x extension that adds support for MessagePack",
-    OsgiKeys.bundleSymbolicName := "org.msgpack.msgpack-jackson",
+    OsgiKeys.bundleSymbolicName := "org.msgpack.jackson3.jackson-dataformat-msgpack",
     OsgiKeys.exportPackage      := Seq("org.msgpack.jackson3", "org.msgpack.jackson3.dataformat"),
     OsgiKeys.importPackage      := Seq("!android.os", "!sun.*"),
-    Test / fork    := true,
-    javacOptions   := Seq("--release", "17"),
-    doc / javacOptions := Seq("--release", "17", "-Xdoclint:none"),
+    Test / fork                 := true,
+    javacOptions                := Seq("--release", "17"),
+    doc / javacOptions          := Seq("--release", "17", "-Xdoclint:none"),
     libraryDependencies ++=
-      Seq(
-        "tools.jackson.core" % "jackson-databind" % "3.1.2",
-        junitInterface
-      ),
+      Seq("tools.jackson.core" % "jackson-databind" % "3.1.2", junitInterface),
     testOptions += Tests.Argument(TestFrameworks.JUnit, "-v"),
-    Jmh / javaOptions ++= Seq(
-      "--add-opens=java.base/java.nio=ALL-UNNAMED",
-      "--add-opens=java.base/sun.nio.ch=ALL-UNNAMED"
-    )
+    Jmh / javaOptions ++=
+      Seq(
+        "--add-opens=java.base/java.nio=ALL-UNNAMED",
+        "--add-opens=java.base/sun.nio.ch=ALL-UNNAMED"
+      )
   )
   .dependsOn(msgpackCore)