Test Serialize/Deserialize Optional with Jackson

jackson/pom.xml

@@ -67,6 +67,12 @@
             <version>${jackson.version}</version>
         </dependency>
 
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jdk8</artifactId>
+            <version>${jackson.version}</version>
+        </dependency>
+
         <dependency>
             <groupId>joda-time</groupId>
             <artifactId>joda-time</artifactId>
@@ -128,8 +134,8 @@
             <version>${mockito.version}</version>
             <scope>test</scope>
         </dependency>
-        
-         <!-- logging -->
+
+        <!-- logging -->
 
         <dependency>
             <groupId>org.slf4j</groupId>
@@ -152,7 +158,7 @@
             <groupId>org.slf4j</groupId>
             <artifactId>log4j-over-slf4j</artifactId>
             <version>${org.slf4j.version}</version>
-</dependency>
+        </dependency>
 
     </dependencies>
 
@@ -198,7 +204,7 @@
         <!-- util -->
         <guava.version>19.0</guava.version>
         <commons-lang3.version>3.5</commons-lang3.version>
-        <commons-io.version>2.5</commons-io.version>        
+        <commons-io.version>2.5</commons-io.version>
         <joda-time.version>2.9.6</joda-time.version>
         <gson.version>2.8.0</gson.version>
         <commons-collections4.version>4.1</commons-collections4.version>

jackson/src/main/java/com/baeldung/jackson/miscellaneous/mixin/Book.java

@@ -0,0 +1,25 @@
+package com.baeldung.jackson.miscellaneous.mixin;
+
+import java.util.Optional;
+
+public class Book {
+
+    private String title;
+    private Optional<String> subTitle;
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Optional<String> getSubTitle() {
+        return subTitle;
+    }
+
+    public void setSubTitle(Optional<String> subTitle) {
+        this.subTitle = subTitle;
+    }
+}

jackson/src/test/java/com/baeldung/jackson/miscellaneous/mixin/OptionalTypeTest.java

@@ -0,0 +1,74 @@
+package com.baeldung.jackson.miscellaneous.mixin;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
+import static io.restassured.path.json.JsonPath.from;
+import java.io.IOException;
+import java.util.Optional;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class OptionalTypeTest {
+
+    ObjectMapper mapper = new ObjectMapper()
+            .registerModule(new Jdk8Module());
+
+    @Test
+    public void givenOptional_whenSerializing_thenValueInJson() throws JsonProcessingException {
+
+        // arrange
+        String subTitle = "The Parish Boy's Progress";
+        Book book = new Book();
+        book.setTitle("Oliver Twist");
+        book.setSubTitle(Optional.of(subTitle));
+
+        // act
+        String result = mapper.writeValueAsString(book);
+
+        // assert
+        assertThat(from(result).getString("subTitle")).isEqualTo(subTitle);
+    }
+
+    @Test
+    public void givenEmptyOptional_whenSerializing_thenNullValue() throws JsonProcessingException {
+
+        // arrange
+        Book book = new Book();
+        book.setTitle("Oliver Twist");
+        book.setSubTitle(Optional.empty());
+
+        // act
+        String result = mapper.writeValueAsString(book);
+
+        // assert
+        assertThat(from(result).getString("subTitle")).isNull();
+    }
+
+    @Test
+    public void givenField_whenDeserializing_thenOptionalWithValue() throws IOException {
+
+        // arrange
+        String subTitle = "The Parish Boy's Progress";
+        String book = "{ \"title\": \"Oliver Twist\", \"subTitle\": \"" + subTitle + "\" }";
+
+        // act
+        Book result = mapper.readValue(book, Book.class);
+
+        // assert
+        assertThat(result.getSubTitle()).isEqualTo(Optional.of(subTitle));
+    }
+
+    @Test
+    public void givenEmptyField_whenDeserializing_thenEmptyOptional() throws IOException {
+
+        // arrange
+        String book = "{ \"title\": \"Oliver Twist\", \"subTitle\": null }";
+
+        // act
+        Book result = mapper.readValue(book, Book.class);
+
+        // assert
+        assertThat(result.getSubTitle()).isEmpty();
+    }
+}