baeldung-articles : BAEL-7644 (#16211)

* baeldung-articles : BAEL-7644

Include null value in JSON serialization (Main)

* baeldung-articles : BAEL-7644

Include null value in JSON serialization (Test).

json-modules/json-conversion/src/main/java/com/baeldung/includenullinjson/Customer.java

@@ -0,0 +1,27 @@
+package com.baeldung.includenullinjson;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class Customer {
+    @JsonProperty
+    private final String name;
+    @JsonProperty
+    private final String address;
+    @JsonProperty
+    private final int age;
+
+    public Customer(String name, String address, int age) {
+        this.name = name;
+        this.address = address;
+        this.age = age;
+    }
+
+    @Override
+    public String toString() {
+        return "Customer{" +
+                "name='" + name + '\'' +
+                ", address='" + address + '\'' +
+                ", age=" + age +
+                '}';
+    }
+}

json-modules/json-conversion/src/test/java/com/baeldung/includenullinjson/IncludeNullValuesInJsonUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.includenullinjson;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class IncludeNullValuesInJsonUnitTest {
+    String expectedJson = "{\"name\":\"John\",\"address\":null,\"age\":25}";
+    Customer obj = new Customer("John", null, 25);
+
+    @Test
+    public void givenObjectWithNullField_whenJacksonUsed_thenIncludesNullValue() throws JsonProcessingException {
+        ObjectMapper mapper = new ObjectMapper();
+        mapper.setSerializationInclusion(JsonInclude.Include.ALWAYS);
+        String json = mapper.writeValueAsString(obj);
+        assertEquals(expectedJson, json);
+    }
+
+    @Test
+    public void givenObjectWithNullField_whenGsonUsed_thenIncludesNullValue() {
+        Gson gson = new GsonBuilder().serializeNulls().create();
+        String json = gson.toJson(obj);
+        assertEquals(expectedJson, json);
+    }
+}