feat(jackson3): add jackson3 support for Java Client generator - WebClient

[phoval]

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---

Summary by cubic

Adds Jackson 3 support to the Java client generator for Spring Boot 4, covering both WebClient and RestTemplate libraries. Introduces a new useJackson3 option, updates templates and docs, and adds Spring Boot 4 sample configs.

• New Features

  • New additionalProperty: useJackson3 (requires useSpringBoot4, incompatible with openApiNullable).
  • WebClient and RestTemplate ApiClient templates now switch imports and runtime components based on Jackson 2 vs 3, including XML converters when enabled.
  • POM templates updated to emit correct Jackson 3 coordinates and Spring Boot 4 compatible dependencies.
  • New sample configs:
    • java-restclient-springBoot4-jackson2.yaml
    • java-restclient-springBoot4-jackson3.yaml
    • java-webclient-springBoot4-jackson3.yaml
  • Docs updated (java.md, java-microprofile.md) to document useJackson3.
  • Misc: RFC3339DateFormat and model templates now use a configurable jacksonPackage; sample builds bump to newer Maven plugins; dev shell uses JDK 17.

• Migration

  • To generate Jackson 3 clients: set useSpringBoot4=true and useJackson3=true.
  • Do not enable openApiNullable with Jackson 3.
  • Build with Java 17+.

^{Written for commit 1a7c61b. Summary will update on new commits.}

[cubic-dev-ai]

6 issues found across 860 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 (all 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/restclient-springBoot4-jackson2/docs/FakeApi.md">

<violation number="1" location="samples/client/petstore/java/restclient-springBoot4-jackson2/docs/FakeApi.md:1007">
P2: The generated example uses `Arrays.asList(-efg)`, which is invalid Java syntax. The enum value "-efg" maps to `EnumClass._EFG`, so the example should reference the enum constant instead of the raw token.</violation>
</file>

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

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/restclient/pom.mustache:351">
P2: When useJackson3 is enabled, the template still includes jackson-databind-nullable, which depends on Jackson 2 (com.fasterxml.jackson.*). This will conflict with Jackson 3’s tools.jackson.* packages and can cause compilation/runtime failures. Guard this dependency for Jackson 3 or provide a compatible alternative.</violation>
</file>

<file name="samples/client/petstore/java/restclient-springBoot4-jackson2/README.md">

<violation number="1" location="samples/client/petstore/java/restclient-springBoot4-jackson2/README.md:100">
P2: README example uses `HttpStatusCodeException` without importing it, so the snippet won’t compile when copied.</violation>
</file>

<file name="samples/client/petstore/java/restclient-springBoot4-jackson2/build.sbt">

<violation number="1" location="samples/client/petstore/java/restclient-springBoot4-jackson2/build.sbt:1">
P2: Invalid comment syntax in build.sbt; '#' is not a Scala comment and will cause sbt parsing to fail.</violation>
</file>

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

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/webclient/ApiClient.mustache:169">
P2: Jackson 3 createDefaultMapper omits JsonNullableModule registration, so openApiNullable types won’t serialize/deserialize correctly.</violation>
</file>

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

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/restclient/ApiClient.mustache:195">
P2: Jackson3 createDefaultMapper builds a JsonMapper without registering JsonNullableModule when openApiNullable is enabled, unlike the Jackson2 branch. JsonNullable requires its module to be registered to serialize/deserialize nullable fields, so Jackson3-generated clients will mishandle JsonNullable values.</violation>
</file>

---

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[cubic-dev-ai]

P2: The generated example uses Arrays.asList(-efg), which is invalid Java syntax. The enum value "-efg" maps to EnumClass._EFG, so the example should reference the enum constant instead of the raw token.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/restclient-springBoot4-jackson2/docs/FakeApi.md, line 1007:

<comment>The generated example uses `Arrays.asList(-efg)`, which is invalid Java syntax. The enum value "-efg" maps to `EnumClass._EFG`, so the example should reference the enum constant instead of the raw token.</comment>

<file context>
@@ -0,0 +1,1541 @@
+        String enumQueryString = "_abc"; // String | Query parameter enum test (string)
+        Integer enumQueryInteger = 1; // Integer | Query parameter enum test (double)
+        Double enumQueryDouble = 1.1D; // Double | Query parameter enum test (double)
+        List<EnumClass> enumQueryModelArray = Arrays.asList(-efg); // List<EnumClass> | 
+        List<String> enumFormStringArray = Arrays.asList("$"); // List<String> | Form parameter enum test (string array)
+        String enumFormString = "_abc"; // String | Form parameter enum test (string)
</file context>

[cubic-dev-ai]

P2: When useJackson3 is enabled, the template still includes jackson-databind-nullable, which depends on Jackson 2 (com.fasterxml.jackson.). This will conflict with Jackson 3’s tools.jackson. packages and can cause compilation/runtime failures. Guard this dependency for Jackson 3 or provide a compatible alternative.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/Java/libraries/restclient/pom.mustache, line 351:

<comment>When useJackson3 is enabled, the template still includes jackson-databind-nullable, which depends on Jackson 2 (com.fasterxml.jackson.*). This will conflict with Jackson 3’s tools.jackson.* packages and can cause compilation/runtime failures. Guard this dependency for Jackson 3 or provide a compatible alternative.</comment>

<file context>
@@ -341,25 +331,42 @@
+        {{#useSpringBoot4}}
+        <spring-web-version>7.0.5</spring-web-version>
+        {{#useJackson3}}
+        <jackson-version>3.0.4</jackson-version>
+        {{/useJackson3}}
+        {{^useJackson3}}
</file context>

[cubic-dev-ai]

P2: README example uses HttpStatusCodeException without importing it, so the snippet won’t compile when copied.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/restclient-springBoot4-jackson2/README.md, line 100:

<comment>README example uses `HttpStatusCodeException` without importing it, so the snippet won’t compile when copied.</comment>

<file context>
@@ -0,0 +1,278 @@
+        try {
+            Client result = apiInstance.call123testSpecialTags(client);
+            System.out.println(result);
+        } catch (HttpStatusCodeException e) {
+            System.err.println("Exception when calling AnotherFakeApi#call123testSpecialTags");
+            System.err.println("Status code: " + e.getStatusCode().value());
</file context>

[cubic-dev-ai]

P2: Invalid comment syntax in build.sbt; '#' is not a Scala comment and will cause sbt parsing to fail.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/restclient-springBoot4-jackson2/build.sbt, line 1:

<comment>Invalid comment syntax in build.sbt; '#' is not a Scala comment and will cause sbt parsing to fail.</comment>

<file context>
@@ -0,0 +1 @@
+# TODO
</file context>

[cubic-dev-ai]

P2: Jackson 3 createDefaultMapper omits JsonNullableModule registration, so openApiNullable types won’t serialize/deserialize correctly.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/Java/libraries/webclient/ApiClient.mustache, line 169:

<comment>Jackson 3 createDefaultMapper omits JsonNullableModule registration, so openApiNullable types won’t serialize/deserialize correctly.</comment>

<file context>
@@ -150,7 +164,21 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
-    public static ObjectMapper createDefaultObjectMapper(@Nullable DateFormat dateFormat) {
+    {{#useJackson3}}
+    public static JsonMapper createDefaultMapper(@Nullable DateFormat dateFormat) {
+        return JsonMapper.builder()
+            .defaultDateFormat(dateFormat)
+            {{#failOnUnknownProperties}}
</file context>

[cubic-dev-ai]

P2: Jackson3 createDefaultMapper builds a JsonMapper without registering JsonNullableModule when openApiNullable is enabled, unlike the Jackson2 branch. JsonNullable requires its module to be registered to serialize/deserialize nullable fields, so Jackson3-generated clients will mishandle JsonNullable values.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/Java/libraries/restclient/ApiClient.mustache, line 195:

<comment>Jackson3 createDefaultMapper builds a JsonMapper without registering JsonNullableModule when openApiNullable is enabled, unlike the Jackson2 branch. JsonNullable requires its module to be registered to serialize/deserialize nullable fields, so Jackson3-generated clients will mishandle JsonNullable values.</comment>

<file context>
@@ -159,7 +182,21 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
+            {{^failOnUnknownProperties}}
+            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+            {{/failOnUnknownProperties}}
+            .build();
+    }
+    {{/useJackson3}}
</file context>