[java][resttemplate] Add support for Jackson 3 and Spring Boot 4 in Java resttemplate

[jorgerod]

Add option to generate Resttemplate using latest spring 7.

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---

Summary by cubic

Adds optional RestTemplate generation for Spring Framework 7 (Spring Boot 4) with Jackson 3. Opt-in only; existing defaults stay the same.

• New Features

  • New flags: useSpringBoot4 and useJackson3 (requires useSpringBoot4; incompatible with openApiNullable).
  • Jackson groupId switches via jacksonPackage; Gradle/POM use jackson_version and align jackson-databind to jackson_version; JSON/XML imports updated.
  • Spring Boot 4 sets spring-web 7.0.5, bean-validation 3.1.1, and Java 17; Jakarta uses spring-web 6.2.x; legacy remains 5.3.x. Jackson 3 drops jackson-datatype-jsr310.
  • Added sample configs and generated samples for resttemplate-springBoot4-jackson2 and -jackson3; CI builds these on JDK 17/21.
  • Maintenance: removed unused test files; added libs.versions.toml and updated sample FILES lists.

• Migration

  • Opt in with -DuseSpringBoot4=true; add -DuseJackson3=true for Jackson 3.
  • Build with JDK 17 when useSpringBoot4=true; with useJackson3=true also set -DopenApiNullable=false.
  • No changes unless these flags are set.

^{Written for commit 5bcd5c0. Summary will update on new commits.}

[cubic-dev-ai]

6 issues found across 562 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/resttemplate-springBoot4-jackson2/docs/EnumArrays.md">

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson2/docs/EnumArrays.md:10">
P2: Enum property links use fragment IDs that don’t match the actual enum heading anchors, causing broken intra-doc navigation.</violation>
</file>

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

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson2/README.md:18">
P2: README lists an incorrect Java minimum version for the Spring Boot 4 sample, which will mislead users into unsupported JDKs.</violation>
</file>

<file name="samples/client/petstore/java/resttemplate-springBoot4-jackson2/docs/FakeApi.md">

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson2/docs/FakeApi.md:1007">
P2: The generated Java example uses `Arrays.asList(-efg)`, which is invalid Java syntax; it should reference a valid enum constant (e.g., `EnumClass._EFG`) or `EnumClass.fromValue("-efg")` so the example compiles.</violation>
</file>

<file name="samples/client/petstore/java/resttemplate-springBoot4-jackson2/.travis.yml">

<violation number="1" location="samples/client/petstore/java/resttemplate-springBoot4-jackson2/.travis.yml:8">
P2: Travis CI matrix uses JDK 8–12, but this sample requires Java 17 (build.gradle sets source/target 17), so CI will fail on these runtimes.</violation>
</file>

<file name=".github/workflows/samples-java-client-jdk17.yaml">

<violation number="1" location=".github/workflows/samples-java-client-jdk17.yaml:32">
P1: New Spring Boot 4 RestTemplate samples were added to the build matrix without corresponding workflow path triggers, so PRs/commits touching only those folders can skip this CI workflow.</violation>
</file>

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

<violation number="1" location="modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/pom.mustache:159">
P2: The new useSpringBoot4 properties block omits beanvalidation-version, but the Bean Validation dependency still references ${beanvalidation-version}. If useSpringBoot4 and useBeanValidation are enabled together, Maven fails with an unresolved property. Define beanvalidation-version in the useSpringBoot4 branch to avoid build failures.</violation>
</file>

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

[cubic-dev-ai]

P2: Enum property links use fragment IDs that don’t match the actual enum heading anchors, causing broken intra-doc navigation.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/resttemplate-springBoot4-jackson2/docs/EnumArrays.md, line 10:

<comment>Enum property links use fragment IDs that don’t match the actual enum heading anchors, causing broken intra-doc navigation.</comment>

<file context>
@@ -0,0 +1,32 @@
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**justSymbol** | [**JustSymbolEnum**](#JustSymbolEnum) |  |  [optional] |
+|**arrayEnum** | [**List&lt;ArrayEnumEnum&gt;**](#List&lt;ArrayEnumEnum&gt;) |  |  [optional] |
+
</file context>

Suggested change

	|**justSymbol** | [**JustSymbolEnum**](#JustSymbolEnum) | | [optional] |
	|**arrayEnum** | [**List<ArrayEnumEnum>**](#List<ArrayEnumEnum>) | | [optional] |
	|**justSymbol** | [**JustSymbolEnum**](#enum-justsymbolenum) | | [optional] |
	|**arrayEnum** | [**List<ArrayEnumEnum>**](#enum-listarrayenumenum) | | [optional] |

[cubic-dev-ai]

P2: README lists an incorrect Java minimum version for the Spring Boot 4 sample, which will mislead users into unsupported JDKs.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/resttemplate-springBoot4-jackson2/README.md, line 18:

<comment>README lists an incorrect Java minimum version for the Spring Boot 4 sample, which will mislead users into unsupported JDKs.</comment>

<file context>
@@ -0,0 +1,278 @@
+
+Building the API client library requires:
+
+1. Java 1.8+
+2. Maven/Gradle
+
</file context>

[cubic-dev-ai]

P2: The generated Java example uses Arrays.asList(-efg), which is invalid Java syntax; it should reference a valid enum constant (e.g., EnumClass._EFG) or EnumClass.fromValue("-efg") so the example compiles.

Prompt for AI agents

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

<comment>The generated Java example uses `Arrays.asList(-efg)`, which is invalid Java syntax; it should reference a valid enum constant (e.g., `EnumClass._EFG`) or `EnumClass.fromValue("-efg")` so the example compiles.</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>

Suggested change

	List<EnumClass> enumQueryModelArray = Arrays.asList(-efg); // List<EnumClass> |
	List<EnumClass> enumQueryModelArray = Arrays.asList(EnumClass._EFG); // List<EnumClass> |

[cubic-dev-ai]

P2: Travis CI matrix uses JDK 8–12, but this sample requires Java 17 (build.gradle sets source/target 17), so CI will fail on these runtimes.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/resttemplate-springBoot4-jackson2/.travis.yml, line 8:

<comment>Travis CI matrix uses JDK 8–12, but this sample requires Java 17 (build.gradle sets source/target 17), so CI will fail on these runtimes.</comment>

<file context>
@@ -0,0 +1,22 @@
+#
+language: java
+jdk:
+  - openjdk12
+  - openjdk11
+  - openjdk10
</file context>

[cubic-dev-ai]

P2: The new useSpringBoot4 properties block omits beanvalidation-version, but the Bean Validation dependency still references ${beanvalidation-version}. If useSpringBoot4 and useBeanValidation are enabled together, Maven fails with an unresolved property. Define beanvalidation-version in the useSpringBoot4 branch to avoid build failures.

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/resttemplate/pom.mustache, line 159:

<comment>The new useSpringBoot4 properties block omits beanvalidation-version, but the Bean Validation dependency still references ${beanvalidation-version}. If useSpringBoot4 and useBeanValidation are enabled together, Maven fails with an unresolved property. Define beanvalidation-version in the useSpringBoot4 branch to avoid build failures.</comment>

<file context>
@@ -156,10 +156,14 @@
                     <target>17</target>
                 {{/useJakartaEe}}
-                {{^useJakartaEe}}
+                {{#useSpringBoot4}}
+                    <source>17</source>
+                    <target>17</target>
</file context>

[wing328]

can you please review the build failure when you've time?

[jorgerod]

can you please review the build failure when you've time?

I have run the tests locally and they are working fine. On GitHub, the error I see is:
/home/runner/work/_temp/291e3712-3492-4639-8a81-c2b055936578.sh: line 1: ./gradlew: Permission denied

@wing328 Can you guide me?

[wing328]

what about copying ./gradlew from one of the existing folders for Java resttemplate client to the new folders you just created in this PR?

e.g. https://github.com/OpenAPITools/openapi-generator/blob/master/samples/client/petstore/java/resttemplate/gradlew

[Mattias-Sehlstedt]

Note that RestTemplate is scheduled to be deprecated. So I would suggest to switch to RestClient if possible.

[jorgerod]

Note that RestTemplate is scheduled to be deprecated. So I would suggest to switch to RestClient if possible.

True, but in my case migrating to RestClient isn't feasible at this time.