fix(kotlin-spring): default Jackson 3 when Spring Boot 4 set via setter or additionalProperties

The Jackson 3 defaulting logic only checked additionalProperties map,
so calling setUseSpringBoot4(true) via the Java API skipped the default.
Now checks both the field value and the map.

Author: yonatankarp

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinSpringServerCodegen.java

@@ -424,9 +424,10 @@ public String getHelp() {
 
     @Override
     public void processOpts() {
-        if (additionalProperties.containsKey(USE_SPRING_BOOT4)
-                && Boolean.parseBoolean(additionalProperties.get(USE_SPRING_BOOT4).toString())
-                && !additionalProperties.containsKey(USE_JACKSON_3)) {
+        boolean springBoot4Enabled = useSpringBoot4
+                || (additionalProperties.containsKey(USE_SPRING_BOOT4)
+                    && Boolean.parseBoolean(additionalProperties.get(USE_SPRING_BOOT4).toString()));
+        if (springBoot4Enabled && !additionalProperties.containsKey(USE_JACKSON_3)) {
             additionalProperties.put(USE_JACKSON_3, "true");
         }
 

modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/spring/KotlinSpringServerCodegenTest.java

@@ -5010,6 +5010,38 @@ public void shouldNotUseLegacyOAuth2WithSpringBoot4CloudLibrary() throws IOExcep
         assertFileContains(clientConfigPath, "ClientRegistrationRepository");
         assertFileContains(clientConfigPath, "OAuth2RequestInterceptor");
     }
+
+    @Test
+    public void shouldDefaultToJackson3WhenSpringBoot4EnabledViaSetter() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        String outputPath = output.getAbsolutePath().replace('\\', '/');
+
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/petstore.yaml");
+        final KotlinSpringServerCodegen codegen = new KotlinSpringServerCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.setOutputDir(output.getAbsolutePath());
+
+        // Set via setter, NOT additionalProperties
+        codegen.setUseSpringBoot4(true);
+        codegen.additionalProperties().put(DOCUMENTATION_PROVIDER, DocumentationProvider.NONE.toCliOptValue());
+        codegen.additionalProperties().put(ANNOTATION_LIBRARY, AnnotationLibrary.NONE.toCliOptValue());
+
+        ClientOptInput input = new ClientOptInput();
+        input.openAPI(openAPI);
+        input.config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.setGenerateMetadata(false);
+        generator.opts(input).generate();
+
+        Path pomPath = Paths.get(outputPath + "/pom.xml");
+        assertFileContains(pomPath, "tools.jackson.dataformat");
+        assertFileContains(pomPath, "tools.jackson.module");
+        assertFileNotContains(pomPath, "com.fasterxml.jackson.dataformat");
+        assertFileNotContains(pomPath, "com.fasterxml.jackson.module");
+        assertFileNotContains(pomPath, "jackson-datatype-jsr310");
+    }
 }