JarCastingjackson-databind-java-optional
A shim library to support mapping Java 8 Optional through Jackson. Forked from @realjenuis jackson-databind-java8 project.
This library is compiled with Java 8 and will thus only be useful in a Java 8 (or higher) runtime environment.
Alternatives
If you are starting a new project that requires support for Java 8 combined with Jackson Databind, you should probably have a look at FasterXML's JDK 8 module.
Usage
The library is distributed through Sonatype's OSS repo
Maven dependency
<dependency>
<groupId>org.zapodot</groupId>
<artifactId>jackson-databind-java-optional</artifactId>
<version>2.6.1</version>
</dependency>
SBT
libraryDependencies += "org.zapodot" % "jackson-databind-java-optional" % "2.6.1"
Registering module
The module is auto-discoverable using the Jackson ObjectMappers's findAndRegisterModules method
final ObjectMapper mapper = new ObjectMapper().findAndRegisterModules();
If you are not to crazy about using auto discovery, you can always register the module manually
final ObjectMapper objectMapper = new ObjectMapper()
.registerModule(
new JavaOptionalModule());
Serialization
Empty Optionals will be serialized as JSON nulls. Example:
public class Bean {
public static final String PRESENT_VALUE = "present";
@JsonProperty
private Optional<String> empty = Optional.empty();
@JsonProperty
private Optional<String> notSet;
@JsonProperty
private Optional<String> present = Optional.of(PRESENT_VALUE);
public static void serialize() {
final ObjectMapper mapper = new ObjectMapper().findAndRegisterModules();
final String json = mapper.writeValueAsString(new Bean());
System.out.println(json); // will print '{"empty":null,"notSet":null,"present":"present"}'
}
}
Deserialization
Nulls will be deserialized as Optional.empty() Example:
public class JavaOptionalDeserializeTest {
public static class Bean {
public static final String PRESENT_VALUE = "present";
@JsonProperty
private Optional<String> empty = Optional.empty();
@JsonProperty
private Optional<String> notSet;
@JsonProperty
private Optional<String> present = Optional.of(PRESENT_VALUE);
}
@Test
public void testDeserialize() throws Exception {
final Bean bean = new ObjectMapper().findAndRegisterModules()
.readValue("{\"empty\":null,\"notSet\":null}", Bean.class);
assertNotNull(bean.empty);
assertEquals(Optional.empty(), bean.empty);
assertNotNull(bean.notSet);
assertEquals(Optional.empty(), bean.notSet);
assertEquals(Optional.of(Bean.PRESENT_VALUE), bean.present);
}
}