Merge pull request #22 from rachelshu/master

Map ignore null value and null key serializer

jackson/src/test/java/org/baeldung/jackson/dtos/MyDtoNullKeySerializer.java

@@ -0,0 +1,19 @@
+package org.baeldung.jackson.dtos;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+public class MyDtoNullKeySerializer extends JsonSerializer<Object> {
+
+    @Override
+    public void serialize(final Object value, final JsonGenerator jgen, final SerializerProvider provider) throws IOException, JsonProcessingException {
+
+        jgen.writeFieldName("");
+
+    }
+
+}

jackson/src/test/java/org/baeldung/jackson/test/JacksonSerializationIgnoreUnitTest.java

@@ -5,9 +5,12 @@ import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertThat;
 
 import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
 
 import org.baeldung.jackson.dtos.MyDto;
 import org.baeldung.jackson.dtos.MyDtoIncludeNonDefault;
+import org.baeldung.jackson.dtos.MyDtoNullKeySerializer;
 import org.baeldung.jackson.dtos.MyDtoWithFilter;
 import org.baeldung.jackson.dtos.MyMixInForString;
 import org.baeldung.jackson.dtos.ignore.MyDtoIgnoreField;
@@ -20,6 +23,7 @@ import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParseException;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.SerializerProvider;
 import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
 import com.fasterxml.jackson.databind.ser.FilterProvider;
@@ -183,4 +187,79 @@ public class JacksonSerializationIgnoreUnitTest {
         System.out.println(dtoAsString);
     }
 
+    @Test
+    public final void givenIgnoringMapNullValue_whenWritingMapObjectWithNullValue_thenIgnored() throws JsonProcessingException {
+        final ObjectMapper mapper = new ObjectMapper();
+        mapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);
+
+        final MyDto dtoObject1 = new MyDto();
+
+        final Map<String, MyDto> dtoMap = new HashMap<String, MyDto>();
+        dtoMap.put("dtoObject1", dtoObject1);
+        dtoMap.put("dtoObject2", null);
+
+        final String dtoMapAsString = mapper.writeValueAsString(dtoMap);
+
+        assertThat(dtoMapAsString, containsString("dtoObject1"));
+        assertThat(dtoMapAsString, not(containsString("dtoObject2")));
+        System.out.println(dtoMapAsString);
+    }
+
+    @Test
+    public final void givenIgnoringMapValueObjectWithNullField_whenWritingMapValueObjectWithNullField_thenIgnored() throws JsonProcessingException {
+        final ObjectMapper mapper = new ObjectMapper();
+        mapper.setSerializationInclusion(Include.NON_NULL);
+
+        final MyDto dtoObject = new MyDto();
+
+        final Map<String, MyDto> dtoMap = new HashMap<String, MyDto>();
+        dtoMap.put("dtoObject", dtoObject);
+
+        final String dtoMapAsString = mapper.writeValueAsString(dtoMap);
+
+        assertThat(dtoMapAsString, containsString("dtoObject"));
+        assertThat(dtoMapAsString, not(containsString("stringValue")));
+        System.out.println(dtoMapAsString);
+    }
+
+    @Test
+    public final void givenAllowingMapObjectWithNullKey_whenWritingMapObjectWithNullKey_thenAllowed() throws JsonProcessingException {
+        final ObjectMapper mapper = new ObjectMapper();
+        mapper.getSerializerProvider().setNullKeySerializer(new MyDtoNullKeySerializer());
+
+        final MyDto dtoObject = new MyDto();
+        dtoObject.setStringValue("dtoObjectString");
+
+        final Map<String, MyDto> dtoMap = new HashMap<String, MyDto>();
+        dtoMap.put(null, dtoObject);
+
+        final String dtoMapAsString = mapper.writeValueAsString(dtoMap);
+
+        assertThat(dtoMapAsString, containsString(""));
+        assertThat(dtoMapAsString, containsString("dtoObjectString"));
+        System.out.println(dtoMapAsString);
+    }
+
+    @Test
+    public final void givenAllowingMapObjectOneNullKey_whenWritingMapObjectWithTwoNullKeys_thenOverride() throws JsonProcessingException {
+        final ObjectMapper mapper = new ObjectMapper();
+        mapper.getSerializerProvider().setNullKeySerializer(new MyDtoNullKeySerializer());
+
+        final MyDto dtoObject1 = new MyDto();
+        dtoObject1.setStringValue("dtoObject1String");
+
+        final MyDto dtoObject2 = new MyDto();
+        dtoObject2.setStringValue("dtoObject2String");
+
+        final Map<String, MyDto> dtoMap = new HashMap<String, MyDto>();
+        dtoMap.put(null, dtoObject1);
+        dtoMap.put(null, dtoObject2);
+
+        final String dtoMapAsString = mapper.writeValueAsString(dtoMap);
+
+        assertThat(dtoMapAsString, not(containsString("dtoObject1String")));
+        assertThat(dtoMapAsString, containsString("dtoObject2String"));
+        System.out.println(dtoMapAsString);
+    }
+
 }