feature/jackson3 native (fixes #22294) by thorstenhirsch · Pull Request #23071 · OpenAPITools/openapi-generator

thorstenhirsch · 2026-02-27T17:21:45Z

Add Jackson 3 support to java-native.

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Summary by cubic

Adds opt‑in Jackson 3 support to the Java native client generator while keeping Jackson 2 as default. Fixes #22294. When enabled it requires Java 17+, improves RFC3339 date/time handling, validates option combos, and ships a native-jackson3 sample wired into CI (JDK 17/21).

New Features
- Opt‑in useJackson3: dynamic imports via {{jacksonPackage}}, switch to JsonMapper with EnumFeature/DateTimeFeature, adopt SerializationContext, update RFC3339 module/Instant deserializer, better anyOf/oneOf, handle JacksonException, remove unused IOException, fix mapper.copy().
- Build/CI: Java 17 source/target for Jackson 3; upgrade to Jackson 3.1.0; pin jackson-annotations 2.21; add java-native-jackson3 config and samples/client/petstore/java/native-jackson3; include sample in samples-java-client-jdk17 workflow; add JDK HttpClient test; enable JUnit 5 and useJUnitPlatform() in native/native-async Gradle builds.
- Validation/docs/configs: fail on unsupported combinations (useJackson3 with openApiNullable, or with unsupported libraries); clarify support matrix (supported for native, and for restclient with useSpringBoot4=true); remove useJackson3 from resttemplate/webclient configs and refresh samples; fix duplicated method names in generated WithHttpInfo docs.
Migration
- Default remains Jackson 2. To opt in for native, set additionalProperties.useJackson3=true and openApiNullable=false (requires Java 17+). For restclient, support requires useSpringBoot4=true.
- useJackson3 is incompatible with openApiNullable and not supported for resttemplate or webclient; the generator now fails on these combinations.

^{Written for commit f45392e. Summary will update on new commits.}

cubic-dev-ai

4 issues found across 304 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/resources/Java/libraries/native/pom.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/native/pom.mustache:268">
P1: Potential compile failure: When useJackson3=true, jackson-databind-nullable dependency is excluded from POM, but pojo.mustache still generates JsonNullable type references if openApiNullable is enabled (default). This causes compilation errors due to missing import org.openapitools.jackson.nullable.JsonNullable.</violation>
</file>

<file name="samples/client/petstore/java/native-jackson3/build.gradle">

<violation number="1" location="samples/client/petstore/java/native-jackson3/build.gradle:87">
P2: JUnit 5 is incompletely configured - missing engine dependency and useJUnitPlatform()</violation>
</file>

<file name="modules/openapi-generator/src/main/resources/Java/libraries/native/model.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/native/model.mustache:50">
P0: Incorrect Jackson 3 annotation package imports. The `jackson-annotations` module deliberately kept `com.fasterxml.jackson.annotation.*` package in Jackson 3 for backward compatibility - only core modules moved to `tools.jackson.*`. Fix: annotation imports should remain as `com.fasterxml.jackson.annotation.*` in the useJackson3 section.</violation>
</file>

<file name="samples/client/petstore/java/native-jackson3/docs/DefaultApi.md">

<violation number="1" location="samples/client/petstore/java/native-jackson3/docs/DefaultApi.md:73">
P2: Documentation method signature contains extra 'fooGet' token, resulting in invalid Java syntax 'ApiResponse<FooGetDefaultResponse> fooGet fooGetWithHttpInfo()'. Should be 'ApiResponse<FooGetDefaultResponse> fooGetWithHttpInfo()'.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

modules/openapi-generator/src/main/resources/Java/libraries/native/model.mustache

modules/openapi-generator/src/main/resources/Java/libraries/native/pom.mustache

samples/client/petstore/java/native-jackson3/build.gradle

samples/client/petstore/java/native-jackson3/docs/DefaultApi.md

...es/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java

modules/openapi-generator/src/main/resources/Java/libraries/native/build.gradle.mustache

modules/openapi-generator/src/main/resources/Java/libraries/native/pom.mustache

modules/openapi-generator/src/main/resources/Java/libraries/native/build.gradle.mustache

thorstenhirsch · 2026-03-01T18:23:18Z

I'm not sure about the JUnit 5 changes in samples/client/... - here's what Claude Sonnet 4.6 says when asked for the reason of these changes:

The sample changes come from two of our template fixes that affect all native library samples, not just the Jackson 3 one:

build.gradle.mustache — we added testRuntimeOnly "junit-jupiter-engine" and test { useJUnitPlatform() } to fix incomplete JUnit 5 configuration. This regenerated
build.gradle in every native library sample (native-async, echo_api/java/native, etc.).

api_doc.mustache — we removed the duplicate {{operationId}} token from WithHttpInfo method signatures. This regenerated all native library API docs (removing the
spurious prefix like > fooGet fooGetWithHttpInfo() → > fooGetWithHttpInfo()).

Sounds reasonable to me. If you don't want them here, but in a separate PR instead, I will revert them here, of course.

thorstenhirsch · 2026-03-01T18:43:05Z

Alright, please do another code review @cubic-dev-ai

cubic-dev-ai · 2026-03-01T18:43:12Z

Alright, please do another code review @cubic-dev-ai

@thorstenhirsch I have started the AI code review. It will take a few minutes to complete.

cubic-dev-ai

3 issues found across 333 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="samples/client/petstore/java/native-jackson3/README.md">

<violation number="1" location="samples/client/petstore/java/native-jackson3/README.md:18">
P1: README incorrectly states Java 11+ requirement but Jackson 3 requires Java 17+. This documentation error will cause build/runtime failures for users following the instructions.</violation>
</file>

<file name="samples/client/petstore/java/native-jackson3/.travis.yml">

<violation number="1" location="samples/client/petstore/java/native-jackson3/.travis.yml:6">
P1: Travis CI uses JDK 11 (oraclejdk11) but Jackson 3.x requires Java 17+</violation>
</file>

<file name="modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache:4">
P1: JsonNullableModule is not registered when useJackson3 is enabled, breaking JsonNullable (de)serialization for models generated with openApiNullable=true</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

samples/client/petstore/java/native-jackson3/README.md

samples/client/petstore/java/native-jackson3/.travis.yml

modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache

…on-databind-nullable

thorstenhirsch · 2026-03-03T10:27:40Z

Sorry, this PR is still not ready. The generated code contains wrong imports. I'm working on it.

thorstenhirsch · 2026-03-03T16:29:04Z

Alright, I've fixed SerializerProvider/SerializationContext, ObjectMapper/JsonMapper issues and error handling with the new JacksonException. Now I could successfully generate a Java client with Jackson 3, all unit tests succeed. Also, I've made sure that Jackson 2 still works.

Now I guess it's finally time to start with human code reviews. And sorry @robinmarechal that I've asked you too early and wasted your time.

bin/configs/java-native-jackson3.yaml

thorstenhirsch · 2026-03-04T22:07:01Z

Lots of getters and setters missing in modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java after I've merged master into this feature branch. Looks like I now need to respect useSpringBoot4, as well. Let me give it a shot ...

cubic-dev-ai

1 issue found across 66 files (changes from recent commits).

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="docs/generators/java.md">

<violation number="1" location="docs/generators/java.md:100">
P2: Documentation for useJackson3 with 'native' library is missing Java 17 requirement. Jackson 3 requires Java 17 but the documentation only mentions 'native' library requires Java 11+, misleading users who may attempt to use useJackson3 on Java 11-16.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

docs/generators/java.md

thorstenhirsch · 2026-03-04T23:03:35Z

Alright, this branch is now aligned with restclient's Jackson 3.1.0, unit tests and the integration test you mentioned succeed. @wing328

docs/generators/java-microprofile.md

Clarify the incompatibility of Jackson 3 with openApiNullable in the documentation.

cubic-dev-ai

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="docs/generators/java-microprofile.md">

<violation number="1" location="docs/generators/java-microprofile.md:100">
P2: Documentation regression: The `useJackson3` option description removes the incompatibility warning for `openApiNullable`, but the generator code (`JavaClientCodegen.java`) still silently disables `openApiNullable` when both options are enabled. This creates a documentation-to-implementation contract mismatch where users expect the combination to work but won't get the expected nullable functionality in generated code.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

docs/generators/java-microprofile.md

Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>

tools/jackson/databind/cfg/DateTimeFeature.class

...es/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java

cubic-dev-ai

5 issues found across 31 files (changes from recent commits).

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="samples/client/petstore/java/webclient-springBoot4-jackson3/build.gradle">

<violation number="1" location="samples/client/petstore/java/webclient-springBoot4-jackson3/build.gradle:131">
P1: The `webclient-springBoot4-jackson3` sample build.gradle replaces Jackson 3 dependencies (`tools.jackson.*:3.1.0`) with Jackson 2 dependencies (`com.fasterxml.jackson.*:2.21.1`), which breaks the sample's purpose of validating Jackson 3 compatibility. Other jackson3 samples like `restclient-springBoot4-jackson3` correctly use Jackson 3 coordinates.</violation>
</file>

<file name="samples/client/petstore/java/resttemplate-springBoot4-jackson3/build.gradle">

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson3/build.gradle:100">
P1: Jackson 3 sample now depends on Jackson 2 artifacts, silently breaking Jackson 3 support validation coverage.</violation>
</file>

<file name="samples/client/petstore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java">

<violation number="1" location="samples/client/petstore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java:19">
P1: The jackson3 sample has been regenerated with Jackson 2 APIs instead of Jackson 3 APIs. The code changed from using `tools.jackson.*` package classes (JacksonJsonEncoder/JacksonJsonDecoder, JsonMapper) to `com.fasterxml.jackson.*` package classes (Jackson2JsonEncoder/Jackson2JsonDecoder, ObjectMapper). This invalidates the sample's purpose of testing Jackson 3.x compatibility with Spring Boot 4, as CI would falsely report Jackson 3 works when it's not actually being tested.</violation>
</file>

<file name="samples/client/petstore/java/resttemplate-springBoot4-jackson3/pom.xml">

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson3/pom.xml:234">
P1: Sample POM 'resttemplate-springBoot4-jackson3' has been downgraded from Jackson 3 (3.1.0) to Jackson 2 (2.21.1), losing the purpose of validating Jackson 3 compatibility. Other jackson3 samples (native-jackson3, restclient-springBoot4-jackson3) correctly use Jackson 3 dependencies.</violation>
</file>

<file name="samples/client/petstore/java/resttemplate-springBoot4-jackson3/src/main/java/org/openapitools/client/RFC3339DateFormat.java">

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson3/src/main/java/org/openapitools/client/RFC3339DateFormat.java:22">
P1: Jackson 3 sample uses incorrect namespace and Jackson 2 dependencies instead of Jackson 3. The code changed from tools.jackson (correct Jackson 3 namespace) to com.fasterxml.jackson (Jackson 2 namespace), while dependencies also reference Jackson 2.21.1. This means the 'jackson3' sample doesn't actually use Jackson 3.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

samples/client/petstore/java/webclient-springBoot4-jackson3/build.gradle

samples/client/petstore/java/resttemplate-springBoot4-jackson3/build.gradle

...ore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java

samples/client/petstore/java/resttemplate-springBoot4-jackson3/pom.xml

...sttemplate-springBoot4-jackson3/src/main/java/org/openapitools/client/RFC3339DateFormat.java

thorstenhirsch · 2026-03-12T22:06:59Z

Feels like going 2 steps back... why do I need to cope with resttemplate and webclient reverting from Jackson 3 to Jackson 2 here? I've synced my forked repo and rebased my branch - but with no effect. Was everything up-to-date already? Seems like this is the point when I got lost regarding resttemplate/webclient.

thorstenhirsch added 2 commits February 27, 2026 14:04

add jackson 3 support to java native

2a9e1e6

upgrade to jackson 3.0.4, fix whitespaces

8f7a982

thorstenhirsch mentioned this pull request Feb 27, 2026

[REQ] Jackson3 support for java libraries #22294

Open

thorstenhirsch marked this pull request as ready for review February 27, 2026 17:39

cubic-dev-ai bot reviewed Feb 27, 2026

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robinmarechal mentioned this pull request Feb 28, 2026

[java][webclient] Jackson3 support for webclient robinmarechal/openapi-generator#1

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robinmarechal suggested changes Feb 28, 2026

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...es/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java Outdated Show resolved Hide resolved

robinmarechal mentioned this pull request Feb 28, 2026

[java][webclient] Jackson3 support for webclient #23072

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robinmarechal suggested changes Feb 28, 2026

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thorstenhirsch added 3 commits March 1, 2026 12:31

remove importMapping.put section

a8fb300

require Java 17 for Jackson 3

b69df0d

fix cubic-dev-ai issues, fix unit tests

caca305

cubic-dev-ai bot reviewed Mar 1, 2026

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fix more cubic-dev-ai findings, includes a solution for missing jacks…

4e39fad

…on-databind-nullable

thorstenhirsch requested a review from robinmarechal March 1, 2026 19:52

thorstenhirsch added 7 commits March 3, 2026 12:54

use SerializationContext instead of SerializerProvider

f13f114

use JsonMapper instead of ObjectMapper for Jackson 3

a1e24d1

also fix Mapper in JSON.java for Jackson 3

e8453d3

update samples

fd4a67c

fix mapper.copy()

19d1296

add JacksonException handling

f118f3f

remove IOException where not thrown anymore

8091162

thorstenhirsch added 3 commits March 3, 2026 22:28

Merge branch 'master' into feature/jackson3-native

45dc531

Update jackson_annotations_version in build.gradle.mustache

bf23069

update samples after rebase

786e186

wing328 added the Enhancement: Feature label Mar 4, 2026

wing328 added this to the 7.21.0 milestone Mar 4, 2026

wing328 reviewed Mar 4, 2026

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bin/configs/java-native-jackson3.yaml Show resolved Hide resolved

thorstenhirsch added 3 commits March 4, 2026 22:38

fix FakeApi integration test

d4bcb59

add native-jackson3 to samples-java-client-jdk17 workflow

9d5e569

Merge branch 'master' into feature/jackson3-native

3bc4c27

thorstenhirsch added 2 commits March 4, 2026 23:14

fix compile errors

fbf011e

update samples and docs

52a5a6b

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thorstenhirsch added 2 commits March 4, 2026 23:46

update Jackson to v3.1.0, use {{jacksonPackage}}

cf4a519

update docs and samples

5d2fb18

wing328 reviewed Mar 5, 2026

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docs/generators/java-microprofile.md Outdated Show resolved Hide resolved

thorstenhirsch added 3 commits March 5, 2026 22:00

Update Jackson 3 compatibility note in documentation

c93e857

Clarify the incompatibility of Jackson 3 with openApiNullable in the documentation.

Merge branch 'OpenAPITools:master' into feature/jackson3-native

b0f9078

update the correct documentation

e801e42

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docs/generators/java-microprofile.md Outdated Show resolved Hide resolved

Update docs/generators/java-microprofile.md once again

4ce631a

Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>

robinmarechal suggested changes Mar 6, 2026

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thorstenhirsch added 5 commits March 12, 2026 22:10

fail when an unsupported combination of parameters is used

7559b58

merge latest changes

8e309b8

update docs

21b2655

add openApiNullable=false

2d4f60f

fix resttemplate and webclient

0c2e88e

cubic-dev-ai bot reviewed Mar 12, 2026

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sync docs: incompatible with openApiNullable

fc5b350

thorstenhirsch force-pushed the feature/jackson3-native branch from ac30f57 to fc5b350 Compare March 12, 2026 22:16

update resttemplate/webclient with ai magic

f45392e

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thorstenhirsch commented Feb 27, 2026 •

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