api

src/main/java/ru/olegcherednik/json/impl/JacksonFactory.java

@@ -31,9 +31,10 @@
 import ru.olegcherednik.json.jackson.JacksonEngine;
 import ru.olegcherednik.json.jackson.datetime.JacksonDateModule;
 import ru.olegcherednik.json.jackson.datetime.JacksonJavaTimeModule;
-import ru.olegcherednik.json.jackson.datetime.serializers.key.JacksonNullKeySerializer;
+import ru.olegcherednik.json.jackson.JacksonNullKeySerializer;
 import ru.olegcherednik.json.jackson.enumid.EnumIdModule;
 
+import java.util.Map;
 import java.util.Objects;
 import java.util.ServiceLoader;
 import java.util.TimeZone;
@@ -69,6 +70,8 @@ private static ObjectMapper config(ObjectMapper mapper, JsonSettings settings) {
             mapper.setTimeZone(TimeZone.getTimeZone(settings.getZoneId()));
 
         mapper.getSerializerProvider().setNullKeySerializer(JacksonNullKeySerializer.INSTANCE);
+        mapper.configOverride(Map.class).setInclude(JsonInclude.Value.construct(JsonInclude.Include.NON_NULL,
+                                                                                JsonInclude.Include.ALWAYS));
 
         return mapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.NONE)
                      .setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY)

src/main/java/ru/olegcherednik/json/jackson/datetime/serializers/key/JacksonKeySerializer.java → src/main/java/ru/olegcherednik/json/jackson/JacksonKeySerializer.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package ru.olegcherednik.json.jackson.datetime.serializers.key;
+package ru.olegcherednik.json.jackson;
 
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.databind.SerializationFeature;

src/main/java/ru/olegcherednik/json/jackson/datetime/serializers/key/JacksonNullKeySerializer.java → src/main/java/ru/olegcherednik/json/jackson/JacksonNullKeySerializer.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package ru.olegcherednik.json.jackson.datetime.serializers.key;
+package ru.olegcherednik.json.jackson;
 
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.databind.JsonSerializer;
@@ -31,10 +31,13 @@
 @NoArgsConstructor(access = AccessLevel.PRIVATE)
 public final class JacksonNullKeySerializer extends JsonSerializer<Object> {
 
+    public static final String NULL_VALUE = "";
+
+
     public static final JacksonNullKeySerializer INSTANCE = new JacksonNullKeySerializer();
 
     @Override
     public void serialize(Object value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
-        gen.writeFieldName("");
+        gen.writeFieldName(NULL_VALUE);
     }
 }

src/main/java/ru/olegcherednik/json/jackson/datetime/deserializers/JacksonJsr310KeyDeserializer.java

@@ -19,6 +19,7 @@
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.KeyDeserializer;
 import lombok.RequiredArgsConstructor;
+import ru.olegcherednik.json.jackson.JacksonNullKeySerializer;
 
 import java.io.IOException;
 import java.time.Instant;
@@ -73,7 +74,9 @@ public static JacksonJsr310KeyDeserializer<ZonedDateTime> zonedDateTime(DateTime
 
     @Override
     public final Object deserializeKey(String key, DeserializationContext ctxt) throws IOException {
-        return "".equals(key) ? null : df.parse(key, query);
+        if (JacksonNullKeySerializer.NULL_VALUE.equals(key))
+            return null;
+        return df.parse(key, query);
     }
 }
 

src/main/java/ru/olegcherednik/json/jackson/datetime/serializers/key/JacksonInstantKeySerializer.java

@@ -16,6 +16,8 @@
 
 package ru.olegcherednik.json.jackson.datetime.serializers.key;
 
+import ru.olegcherednik.json.jackson.JacksonKeySerializer;
+
 import java.time.Instant;
 import java.time.format.DateTimeFormatter;
 

src/main/java/ru/olegcherednik/json/jackson/datetime/serializers/key/JacksonOffsetDateTimeKeySerializer.java

@@ -16,6 +16,8 @@
 
 package ru.olegcherednik.json.jackson.datetime.serializers.key;
 
+import ru.olegcherednik.json.jackson.JacksonKeySerializer;
+
 import java.time.OffsetDateTime;
 import java.time.format.DateTimeFormatter;
 

src/main/java/ru/olegcherednik/json/jackson/datetime/serializers/key/JacksonZonedDateTimeKeySerializer.java

@@ -16,6 +16,8 @@
 
 package ru.olegcherednik.json.jackson.datetime.serializers.key;
 
+import ru.olegcherednik.json.jackson.JacksonKeySerializer;
+
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 

src/test/java/ru/olegcherednik/json/jackson/MapNullKeyValueTest.java

@@ -0,0 +1,29 @@
+package ru.olegcherednik.json.jackson;
+
+import org.testng.annotations.Test;
+import ru.olegcherednik.json.api.Json;
+
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Oleg Cherednik
+ * @since 06.02.2024
+ */
+@Test
+public class MapNullKeyValueTest {
+
+    public void shouldSerializeNulWhenWriteMap() {
+        Map<String, String> expected = MapUtils.of("one", "1",
+                                                   "two", null);
+        String json = Json.writeValue(expected);
+        assertThat(json).isNotNull();
+        assertThat(json).isEqualTo("{\"one\":\"1\",\"two\":null}");
+
+        Map<String, String> actual = Json.readMap(json, String.class, String.class);
+        assertThat(actual).isEqualTo(expected);
+
+    }
+
+}

src/test/java/ru/olegcherednik/json/jackson/datetime/deserializers/JacksonJsr310KeyDeserializerTest.java

@@ -33,7 +33,7 @@
 @SuppressWarnings("NewClassNamingConvention")
 public class JacksonJsr310KeyDeserializerTest {
 
-    public void shouldSerializeNullKeyAsEmptyString() {
+    public void shouldSerializeNullKeyAsNullString() {
         LocalDate one = LocalDate.parse("2023-05-05");
         LocalDate two = LocalDate.parse("2023-06-06");