replace stream api usage on Map with dedicated for loop

Author: christophstrobl

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java

@@ -674,12 +674,13 @@ public <T> T getPropertyValue(MongoPersistentProperty property) {
 		}
 
 		if (!documentField.getProperty().isMap() && sourceValue instanceof Document document) {
-			return new Document(document.entrySet().stream().collect(Collectors.toMap(Entry::getKey, entry -> {
-				if (isKeyword(entry.getKey())) {
-					return getMappedValue(documentField, entry.getValue());
+
+			return BsonUtils.mapValues(document, (key, val) -> {
+				if (isKeyword(key)) {
+					return getMappedValue(documentField, val);
 				}
-				return entry.getValue();
-			})));
+				return val;
+			});
 		}
 
 		return valueConverter.write(value, conversionContext);

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/util/BsonUtils.java

@@ -20,9 +20,12 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.StringJoiner;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.stream.StreamSupport;
 
@@ -716,6 +719,23 @@ public static Collection<?> asCollection(Object source) {
 		return source.getClass().isArray() ? CollectionUtils.arrayToList(source) : Collections.singleton(source);
 	}
 
+	public static Document mapValues(Document source, BiFunction<String, Object, Object> valueMapper) {
+		return mapEntries(source, Entry::getKey, entry -> valueMapper.apply(entry.getKey(), entry.getValue()));
+	}
+
+	public static Document mapEntries(Document source, Function<Entry<String,Object>,String> keyMapper, Function<Entry<String,Object>,Object> valueMapper) {
+
+		if(source.isEmpty()) {
+			return source;
+		}
+
+		Map<String, Object> target = new LinkedHashMap<>(source.size(), 1f);
+		for(Entry<String,Object> entry : source.entrySet()) {
+			target.put(keyMapper.apply(entry), valueMapper.apply(entry));
+		}
+		return new Document(target);
+	}
+
 	@Nullable
 	private static String toJson(@Nullable Object value) {
 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/util/json/BsonUtilsTest.java

@@ -29,6 +29,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.stream.Stream;
 
 import org.bson.BsonArray;
@@ -180,6 +181,52 @@ void resolveValueForField(FieldName fieldName, boolean exists) {
 		}
 	}
 
+	@Test
+	void retainsOrderWhenMappingValues() {
+
+		Document source = new Document();
+		source.append("z", "first-entry");
+		source.append("a", "second-entry");
+		source.append("0", "third-entry");
+		source.append("9", "fourth-entry");
+
+		Document target = BsonUtils.mapValues(source, (key, value) -> value);
+		assertThat(source).isNotSameAs(target).containsExactlyEntriesOf(source);
+	}
+
+	@Test
+	void retainsOrderWhenMappingKeys() {
+
+		Document source = new Document();
+		source.append("z", "first-entry");
+		source.append("a", "second-entry");
+
+		Document target = BsonUtils.mapEntries(source, entry -> entry.getKey().toUpperCase(), Entry::getValue);
+		assertThat(target).containsExactly(Map.entry("Z", "first-entry"), Map.entry("A", "second-entry"));
+	}
+
+	@Test
+	void appliesValueMapping() {
+		Document source = new Document();
+		source.append("z", "first-entry");
+		source.append("a", "second-entry");
+
+		Document target = BsonUtils.mapValues(source,
+				(key, value) -> new StringBuilder(value.toString()).reverse().toString());
+		assertThat(target).containsValues("yrtne-tsrif", "yrtne-dnoces");
+	}
+
+	@Test
+	void appliesKeyMapping() {
+
+		Document source = new Document();
+		source.append("z", "first-entry");
+		source.append("a", "second-entry");
+
+		Document target = BsonUtils.mapEntries(source, entry -> entry.getKey().toUpperCase(), Entry::getValue);
+		assertThat(target).containsKeys("Z", "A");
+	}
+
 	static Stream<Arguments> fieldNames() {
 		return Stream.of(//
 				Arguments.of(FieldName.path("a"), true), //