import java.io.IOException; 
import java.text.ParseException; 

import com.fasterxml.jackson.annotation.JsonEnumDefaultValue; 
import com.fasterxml.jackson.databind.DeserializationFeature; 
import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonTester {
   public static void main(String args[]) throws ParseException{
      ObjectMapper mapper = new ObjectMapper();
      mapper.enable(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE);
      String jsonString = "\"abc\""; 
      try {
         LETTERS value = mapper.readValue(jsonString, LETTERS.class); 
         System.out.println(value); 
      }
      catch (IOException e) { 
         e.printStackTrace(); 
      }   
   }  
}
enum LETTERS {
   A, B, @JsonEnumDefaultValue UNKNOWN 
} 

UNKNOWN