JsonEnumDefaultValue annotation can be used on an enum element to define a default (fallback) value used during deserialize. The default enum element value is used if unknown value found in input JSON. This annotation is only applicable when the READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE deserialization feature is enabled.

Example

Example Enum

public enum EmployeeType {
    FullTime,
    PartTime,
    @JsonEnumDefaultValue
    Contractor;
}

Deserializing JSON

In following example we are using a valid value of the enum:

public class ExampleMain {
    public static void main(String[] args) throws IOException {
        String jsonString = "\"FullTime\"";
        System.out.println("-- Json string to deserialize --");
        System.out.println(jsonString);

        ObjectMapper om = new ObjectMapper();
        om.enable(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE);
        EmployeeType type = om.readValue(jsonString, EmployeeType.class);
        System.out.println("-- after deserialization --");
        System.out.println(type);
    }
}

-- Json string to deserialize --
"FullTime"
-- after deserialization --
FullTime

Let's use a value which is not defined in our enum:

public class ExampleMain2 {
    public static void main(String[] args) throws IOException {
        String jsonString = "\"remote\"";
        System.out.println("-- Json string to deserialize --");
        System.out.println(jsonString);

        ObjectMapper om = new ObjectMapper();
        om.enable(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE);
        EmployeeType type = om.readValue(jsonString, EmployeeType.class);
        System.out.println("-- after deserialization --");
        System.out.println(type);
    }
}

-- Json string to deserialize --
"remote"
-- after deserialization --
Contractor

Example Project

Dependencies and Technologies Used:

• jackson-databind 2.9.6: General data-binding functionality for Jackson: works on core streaming API.
• JDK 10
• Maven 3.5.4