[BUG][openapi-yaml] Preserve field order in auto-generated object-level examples (#23664)

modules/openapi-generator/src/main/java/org/openapitools/codegen/examples/ExampleGenerator.java

@@ -351,7 +351,7 @@ private Object resolveModelToExample(String name, String mediaType, Schema schem
         }
 
         processedModels.add(name);
-        Map<String, Object> values = new HashMap<>();
+        Map<String, Object> values = new LinkedHashMap<>();
         LOGGER.debug("Resolving model '{}' to example", name);
         if (schema.getExample() != null) {
             LOGGER.debug("Using example from spec: {}", schema.getExample());

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

@@ -1,6 +1,8 @@
 package org.openapitools.codegen;
 
 import io.swagger.v3.oas.models.OpenAPI;
+import io.swagger.v3.oas.models.media.Schema;
+import io.swagger.v3.oas.models.media.IntegerSchema;
 import org.openapitools.codegen.examples.ExampleGenerator;
 import org.testng.annotations.Test;
 
@@ -11,6 +13,7 @@
 
 import static org.testng.AssertJUnit.assertEquals;
 import static org.testng.AssertJUnit.assertNull;
+import static org.testng.AssertJUnit.assertTrue;
 
 public class ExampleGeneratorTest {
     @Test
@@ -334,4 +337,77 @@ public void generateFromResponseSchemaWithAnyOfComposedModel() {
         assertEquals(String.format(Locale.ROOT, "{%n  \"example_schema_property\" : \"example schema property value\"%n}"), examples.get(0).get("example"));
         assertEquals("200", examples.get(0).get("statusCode"));
     }
+
+    @Test
+    public void testExamplePropertyOrderPreservation() {
+        OpenAPI openAPI = new OpenAPI();
+
+        // Create a schema with properties in a specific order
+        Schema<?> testSchema = new Schema<>();
+        testSchema.setType("object");
+
+        // Use LinkedHashMap to preserve property order as defined in spec
+        Map<String, Schema> properties = new LinkedHashMap<>();
+
+        // Add properties in the specific order: zebra, apple, mango, cherry, banana
+        IntegerSchema zebraSchema = new IntegerSchema();
+        zebraSchema.setExample(1);
+        properties.put("zebra", zebraSchema);
+
+        IntegerSchema appleSchema = new IntegerSchema();
+        appleSchema.setExample(2);
+        properties.put("apple", appleSchema);
+
+        IntegerSchema mangoSchema = new IntegerSchema();
+        mangoSchema.setExample(3);
+        properties.put("mango", mangoSchema);
+
+        IntegerSchema cherrySchema = new IntegerSchema();
+        cherrySchema.setExample(4);
+        properties.put("cherry", cherrySchema);
+
+        IntegerSchema bananaSchema = new IntegerSchema();
+        bananaSchema.setExample(5);
+        properties.put("banana", bananaSchema);
+
+        testSchema.setProperties(properties);
+
+        // Create examples map
+        Map<String, Schema> examples = new HashMap<>();
+        examples.put("TestModel", testSchema);
+
+        // Generate the example using the model name approach
+        ExampleGenerator generator = new ExampleGenerator(examples, openAPI);
+        Set<String> mediaTypeKeys = new TreeSet<>();
+        mediaTypeKeys.add("application/json");
+
+        List<Map<String, String>> generatedExamples = generator.generate(null, new ArrayList<>(mediaTypeKeys), "TestModel");
+
+        assertEquals(1, generatedExamples.size());
+        String exampleOutput = generatedExamples.get(0).get("example");
+
+        System.out.println("Generated example output: " + exampleOutput);
+
+        // Verify the example contains properties in the correct order
+        // The order should be: zebra, apple, mango, cherry, banana
+        assertTrue(exampleOutput.contains("\"zebra\" : 1"));
+        assertTrue(exampleOutput.contains("\"apple\" : 2"));
+        assertTrue(exampleOutput.contains("\"mango\" : 3"));
+        assertTrue(exampleOutput.contains("\"cherry\" : 4"));
+        assertTrue(exampleOutput.contains("\"banana\" : 5"));
+
+        // Verify the order by checking the position of each field in the string
+        int zebraPos = exampleOutput.indexOf("\"zebra\"");
+        int applePos = exampleOutput.indexOf("\"apple\"");
+        int mangoPos = exampleOutput.indexOf("\"mango\"");
+        int cherryPos = exampleOutput.indexOf("\"cherry\"");
+        int bananaPos = exampleOutput.indexOf("\"banana\"");
+
+        System.out.println("Field positions: zebra=" + zebraPos + ", apple=" + applePos + ", mango=" + mangoPos + ", cherry=" + cherryPos + ", banana=" + bananaPos);
+
+        assertTrue("zebra should come before apple", zebraPos < applePos);
+        assertTrue("apple should come before mango", applePos < mangoPos);
+        assertTrue("mango should come before cherry", mangoPos < cherryPos);
+        assertTrue("cherry should come before banana", cherryPos < bananaPos);
+    }
 }