Keep Order of Fields like in the given Java Bean (#76)

* Adding Fields Order flag tot he object mapper

* add test

* do not use for deserz.

* fix merge conflict

* remove unused imports

Author: jenspapenhagen

src/main/java/dev/toonformat/jtoon/util/ObjectMapperSingleton.java

@@ -1,6 +1,7 @@
 package dev.toonformat.jtoon.util;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
+import tools.jackson.databind.MapperFeature;
 import tools.jackson.databind.ObjectMapper;
 import tools.jackson.databind.json.JsonMapper;
 import tools.jackson.module.afterburner.AfterburnerModule;
@@ -30,10 +31,8 @@ public static ObjectMapper getInstance() {
             INSTANCE = JsonMapper.builder()
                 .changeDefaultPropertyInclusion(incl -> incl.withValueInclusion(JsonInclude.Include.ALWAYS))
                 .addModule(new AfterburnerModule()) // Speeds up Jackson by 20–40% in most real-world cases
-                // .disable(MapperFeature.DEFAULT_VIEW_INCLUSION) in Jackson 3 this is default disabled
-                // .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES) in Jackson 3 this is default disabled
-                // .configure(SerializationFeature.INDENT_OUTPUT, false)  in Jackson 3 this is default false
                 .defaultTimeZone(TimeZone.getTimeZone("UTC")) // set a default timezone for dates
+                .disable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY)
                 .build();
         }
         return INSTANCE;

src/test/java/dev/toonformat/jtoon/JToonTest.java

@@ -9,6 +9,7 @@
 import java.lang.reflect.InvocationTargetException;
 import java.math.BigInteger;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -1200,6 +1201,24 @@ void encodesListOfAnnotatedPOJOs() {
                                   102,Monitor,299.99""",
                         encode(obj));
             }
+
+            @Test
+            @DisplayName("encodes nested POJO with keeping the order")
+            void encodesNestedWithKeepingTheOrder() {
+                List<HotelInfoLlmRerankDTO> hotelList = new ArrayList<>();
+                for (int i = 0; i < 5; i++) {
+                    hotelList.add(new HotelInfoLlmRerankDTO("A" + (i + 1),
+                        "hotelId " + i,
+                        "hotelName",
+                        "hotelBrand",
+                        "hotelCategory",
+                        "hotelPrice",
+                        "hotelAddressDistance"
+                    ));
+                }
+
+                assertTrue(encode(hotelList).startsWith("[5]{no,hotelId,hotelName,hotelBrand,hotelCategory,hotelPrice,hotelAddressDistance}:"));
+            }
         }
     }
     @Test

src/test/java/dev/toonformat/jtoon/TestPojos.java

@@ -124,5 +124,16 @@ public record AnnotatedEmployee(
             Address address,
             @JsonIgnore String ssn) {
     }
+
+    /**
+     * Record for checking the field order in the output.
+     */
+    public record HotelInfoLlmRerankDTO(String no,
+                                        String hotelId,
+                                        String hotelName,
+                                        String hotelBrand,
+                                        String hotelCategory,
+                                        String hotelPrice,
+                                        String hotelAddressDistance) {}
 }