diff --git a/modules/openapi-generator/src/main/resources/JavaSpring/apiDelegate.mustache b/modules/openapi-generator/src/main/resources/JavaSpring/apiDelegate.mustache
index a14a42a8d0b7..060df0fc84c4 100644
--- a/modules/openapi-generator/src/main/resources/JavaSpring/apiDelegate.mustache
+++ b/modules/openapi-generator/src/main/resources/JavaSpring/apiDelegate.mustache
@@ -27,6 +27,9 @@ import java.util.Optional;
 {{#async}}
 import java.util.concurrent.CompletableFuture;
 {{/async}}
+{{#returnSuccessCode}}
+import java.util.concurrent.atomic.AtomicInteger;
+{{/returnSuccessCode}}
 import {{javaxPackage}}.annotation.Generated;
 
 {{#operations}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
index 54b0e81ac9d1..9390923cbf97 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
@@ -5575,4 +5575,36 @@ public void testGenericReturnTypeWhenNotUsingResponseEntity_issue1096() throws I
                 .toFileAssert()
                 .assertMethod("findPetsByStatus").hasReturnType("List<Pet>");
     }
+
+    @Test
+    public void testHasRestControllerDoesNotHaveController_issue21156() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_1/issue_21156.yaml");
+        final SpringCodegen codegen = new SpringCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.setLibrary("spring-boot");
+
+        codegen.additionalProperties().put(INTERFACE_ONLY, "false");
+        codegen.additionalProperties().put(DELEGATE_PATTERN, "true");
+        codegen.additionalProperties().put(SPRING_CONTROLLER, "true");
+        codegen.additionalProperties().put(RETURN_SUCCESS_CODE, "true");
+
+        ClientOptInput input = new ClientOptInput();
+        input.openAPI(openAPI);
+        input.config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.setGenerateMetadata(false); // skip metadata generation
+        generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
+
+        Map<String, File> files = generator.opts(input).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApiDelegate.java"));
+        javaFileAssert
+                .hasImports("java.util.concurrent.atomic.AtomicInteger");
+    }
 }
diff --git a/modules/openapi-generator/src/test/resources/3_1/issue_21156.yaml b/modules/openapi-generator/src/test/resources/3_1/issue_21156.yaml
new file mode 100644
index 000000000000..9b1882ba9791
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_1/issue_21156.yaml
@@ -0,0 +1,45 @@
+openapi: 3.1.1
+info:
+  title: Test Bug
+  version: 1.0.0
+servers:
+  - url: https://where.am.i
+paths:
+  /test/bug:
+    post:
+      operationId: testRequest
+      requestBody:
+        content:
+          application/x-www-form-urlencoded:
+            schema:
+              $ref: '#/components/schemas/TestRequest'
+      responses:
+        '200':
+          description: Test request successful
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/TestResponse'
+        '500':
+          $ref: '#/components/responses/InternalServerError'
+components:
+  schemas:
+    TestRequest:
+      properties:
+        test:
+          type: string
+    TestResponse:
+      properties:
+        test:
+          type: string
+    ErrorResponse:
+      properties:
+        error:
+          type: string
+  responses:
+    InternalServerError:
+      content:
+        application/json:
+          schema:
+            $ref: '#/components/schemas/ErrorResponse'
+      description: Internal server error
\ No newline at end of file