asmhatre/jackson2-to-3-migration
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Jackson 2 to 3 migration companion code

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Three Maven modules - jackson2-before (2.22.1), jackson3-after (3.2.1) and a
coexistence module with BOTH majors on one classpath - so every claim in the two
migration guides is executed rather than asserted. Paired class names make the
before/after outputs directly diffable via run-all.sh.

Confirms the guides on wire-format equivalence (10-case suite, zero mismatches),
classpath coexistence and the collapse of four artifacts into one. Corrects nine
points, including that enableDefaultTyping() is still present in Jackson 2.22.1
rather than removed in 2.16, and that the published "after" mapper snippet does
not compile.
This commit is contained in:
Ankur
2026-08-04 23:12:25 +05:30
commit f0a7053fc9
43 changed files with 1665 additions and 0 deletions
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jackson2-before/pom.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.ankurm</groupId>
<artifactId>jackson2-to-3-migration</artifactId>
<version>1.0.0</version>
</parent>
<artifactId>jackson2-before</artifactId>
<name>jackson2-before</name>
<description>The "before" side: Jackson 2 with the three modules it needs</description>
<dependencies>
<!-- Jackson 2 group ID: com.fasterxml.jackson.core -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson2.version}</version>
</dependency>
<!-- java.time support: a SEPARATE artifact in Jackson 2. Gone in Jackson 3. -->
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
<version>${jackson2.version}</version>
</dependency>
<!-- Optional<T> support: a SEPARATE artifact in Jackson 2. Gone in Jackson 3. -->
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jdk8</artifactId>
<version>${jackson2.version}</version>
</dependency>
<!-- Reliable record deserialisation: a SEPARATE artifact in Jackson 2. Gone in Jackson 3. -->
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-parameter-names</artifactId>
<version>${jackson2.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<!-- Jackson 2 needs -parameters for constructor-based deserialisation.
Jackson 3 does not; jackson3-after has no compilerArgs at all. -->
<compilerArgs><arg>-parameters</arg></compilerArgs>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>