fix #796 where order of object nodes attributes is not kept

Author: glhez

json-unit-core/src/main/java/net/javacrumbs/jsonunit/core/internal/Node.java

@@ -16,12 +16,15 @@
 package net.javacrumbs.jsonunit.core.internal;
 
 import static java.util.stream.Collectors.toUnmodifiableSet;
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.toCollection;
 import static net.javacrumbs.jsonunit.core.internal.JsonUtils.prettyPrint;
 
 import java.math.BigDecimal;
 import java.util.AbstractMap;
 import java.util.Collections;
 import java.util.Iterator;
+import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.Set;
 import java.util.Spliterators;
@@ -233,10 +236,9 @@ class JsonMap extends AbstractMap<String, Object> implements NodeWrapper {
         public Set<Entry<String, Object>> entrySet() {
             if (entrySet == null) {
                 Iterator<KeyValue> fields = wrappedNode.fields();
-                entrySet = StreamSupport.stream(Spliterators.spliteratorUnknownSize(fields, 0), false)
-                        .map(keyValue -> new SimpleEntry<>(
-                                keyValue.getKey(), keyValue.getValue().getValue()))
-                        .collect(toUnmodifiableSet());
+                entrySet = StreamSupport.stream(Spliterators.spliteratorUnknownSize(fields, java.util.Spliterator.ORDERED), false)
+                                        .map(keyValue -> new SimpleEntry<>(keyValue.getKey(), keyValue.getValue().getValue()))
+                                        .collect(collectingAndThen(toCollection(LinkedHashSet::new), Collections::unmodifiableSet));
             }
             return entrySet;
         }

tests/test-base/src/main/java/net/javacrumbs/jsonunit/test/base/AbstractAssertJTest.java

@@ -270,6 +270,15 @@ void objectShouldContainComplexValueError() {
                   {"c":5}""");
     }
 
+    @Test
+    void objectFieldsShouldBeKeptInOrder() {
+        assertThatJson("{\"root\":{\"key3\": 3, \"key2\": 2, \"key1\": 1 }}").node("root")
+            .isObject()
+            .containsExactly(entry("key3", 3),
+                             entry("key2", 2),
+                             entry("key1", 1));
+    }
+
     @Test
     void objectDoesContainComplexValue() {
         assertThatJson("{\"a\":1, \"b\": {\"c\" :3}}")