[BUG][JAVA] Add @Nullable to resttemplate api method parameters

[SubhamAshok]

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the checklist and does not contain an issue number.
• Ran the generator tests (JavaClientCodegenTest).

Description

When useJspecify=true, package-info files are marked with @NullMarked. For the resttemplate library, API operation methods previously emitted raw parameter types without @Nullable, causing static analysis tools to flag optional parameters as non-null.

This change updates resttemplate/api.mustache to use {{>nullableArgumentForApi}}, matching webclient and restclient. It also enables the corresponding assertions in JavaClientCodegenTest and updates the sample output.

Fixes #23656.

---

Summary by cubic

Adds @Nonnull and @Nullable annotations to resttemplate API method parameters so required and optional parameters are explicit to static analysis tools. Previously generated methods had no nullability annotations, which made optional parameters look non-null under JSpecify @NullMarked packages. api.mustache now uses the same nullable argument partial as webclient and restclient. Fixes #23656.

• Enables the existing JSpecify parameter assertions in JavaClientCodegenTest for resttemplate.
• Regenerates the resttemplate samples, including the resttemplate-springBoot4-jackson3-jspecify sample.

^{Written for commit 69f0fd4. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

_{Re-trigger cubic}

[wing328]

please update the samples to fix https://github.com/OpenAPITools/openapi-generator/actions/runs/35515230440/job/106090355898?pr=24970 when you've time.

[SubhamAshok]

@wing328 Thanks, I have updated the resttemplate samples.

[cubic-dev-ai]

1 issue found across 29 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/resttemplate/src/main/java/org/openapitools/client/api/FakeApi.java">

<violation number="1" location="samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/api/FakeApi.java:459">
P2: `testBodyWithBinary`/`testBodyWithBinaryWithHttpInfo` annotate the required `body` parameter `@javax.annotation.Nullable`, but the generated body immediately throws `HttpClientErrorException` when `body == null` ("verify the required parameter 'body' is set"). The Javadoc also marks it `(required)`. Marking a parameter nullable while the method rejects null at runtime misleads the static analyzers this PR targets (under `@NullMarked`, callers may pass null and only fail at runtime). The spec schema is nullable, so the required-null-check and the annotation are inconsistent; decide one: emit `@Nullable` and skip the required-null-check for schema-nullable required params, or keep the null check and emit `@Nonnull`. Note the same generated output already exists in the webclient/restclient samples, so the root cause is in the shared `nullableArgumentForApi`/`nullable_var_annotations` logic that this PR adopts for resttemplate.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: testBodyWithBinary/testBodyWithBinaryWithHttpInfo annotate the required body parameter @javax.annotation.Nullable, but the generated body immediately throws HttpClientErrorException when body == null ("verify the required parameter 'body' is set"). The Javadoc also marks it (required). Marking a parameter nullable while the method rejects null at runtime misleads the static analyzers this PR targets (under @NullMarked, callers may pass null and only fail at runtime). The spec schema is nullable, so the required-null-check and the annotation are inconsistent; decide one: emit @Nullable and skip the required-null-check for schema-nullable required params, or keep the null check and emit @Nonnull. Note the same generated output already exists in the webclient/restclient samples, so the root cause is in the shared nullableArgumentForApi/nullable_var_annotations logic that this PR adopts for resttemplate.

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/src/main/java/org/openapitools/client/api/FakeApi.java, line 459:

<comment>`testBodyWithBinary`/`testBodyWithBinaryWithHttpInfo` annotate the required `body` parameter `@javax.annotation.Nullable`, but the generated body immediately throws `HttpClientErrorException` when `body == null` ("verify the required parameter 'body' is set"). The Javadoc also marks it `(required)`. Marking a parameter nullable while the method rejects null at runtime misleads the static analyzers this PR targets (under `@NullMarked`, callers may pass null and only fail at runtime). The spec schema is nullable, so the required-null-check and the annotation are inconsistent; decide one: emit `@Nullable` and skip the required-null-check for schema-nullable required params, or keep the null check and emit `@Nonnull`. Note the same generated output already exists in the webclient/restclient samples, so the root cause is in the shared `nullableArgumentForApi`/`nullable_var_annotations` logic that this PR adopts for resttemplate.</comment>

<file context>
@@ -456,7 +456,7 @@ public ResponseEntity<Void> testAdditionalPropertiesReferenceWithHttpInfo(Map<St
      * @throws RestClientException if an error occurs while attempting to invoke the API
      */
-    public void testBodyWithBinary(File body) throws RestClientException {
+    public void testBodyWithBinary(@javax.annotation.Nullable File body) throws RestClientException {
         testBodyWithBinaryWithHttpInfo(body);
     }
</file context>