fix(spring): Add Nullable import for array-type models (#22788)

Author: spider-yamet

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

@@ -968,11 +968,6 @@ public void postProcessModelProperty(CodegenModel model, CodegenProperty propert
         if (model.getVendorExtensions().containsKey("x-jackson-optional-nullable-helpers")) {
             model.imports.add("Arrays");
         }
-
-        // to prevent inheritors (JavaCamelServerCodegen etc.) mistakenly use it
-        if (getName().contains("spring")) {
-            model.imports.add("Nullable");
-        }
     }
 
     @Override
@@ -989,6 +984,11 @@ public CodegenModel fromModel(String name, Schema model) {
             codegenModel.imports.remove("Schema");
         }
 
+        // Add Nullable import for all models including array-type models (issue #22788)
+        if (getName().contains("spring")) {
+            codegenModel.imports.add("Nullable");
+        }
+
         return codegenModel;
     }
 

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

@@ -6223,4 +6223,37 @@ public void testExtensionsOnSchema_issue9183() throws IOException {
                                                                          ));
     }
 
+    @Test
+    public void shouldAddNullableImportForArrayTypeModels() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec(
+                "src/test/resources/3_0/spring/petstore-with-fake-endpoints-models-for-testing-with-spring-pageable.yaml");
+        final SpringCodegen codegen = new SpringCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put(INTERFACE_ONLY, "true");
+        codegen.additionalProperties().put(CodegenConstants.GENERATE_ALIAS_AS_MODEL, "true");
+
+        ClientOptInput input = new ClientOptInput();
+        input.openAPI(openAPI);
+        input.config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.setGenerateMetadata(false);
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_TESTS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_DOCS, "false");
+
+        Map<String, File> files = generator.opts(input).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        // AnimalFarm is an array-type model with no properties (issue #22788)
+        JavaFileAssert.assertThat(files.get("AnimalFarm.java"))
+                .hasImports("org.springframework.lang.Nullable");
+        JavaFileAssert.assertThat(files.get("Pet.java"))
+                .hasImports("org.springframework.lang.Nullable");
+    }
+
 }