Jackson Annotations - @JsonEnumDefaultValue

Overview

@JsonEnumDefaultValue annotation is used to deserialize an unknown enum value using a default value.

Example - Deserialization without using @JsonEnumDefaultValue

JacksonTester.java

package com.tutorialspoint;

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();
      String jsonString = "\"abc\""; 
      try {
         LETTERS value = mapper.readValue(jsonString, LETTERS.class); 
         System.out.println(value); 
      }
      catch (IOException e) { 
         e.printStackTrace(); 
      }   
   }  
}
enum LETTERS {
   A, B 
} 

Output

Run the JacksonTester and verify the output −

com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type 'com.tutorialspoint.LETTERS' from String "abc": not one of the values accepted for Enum class: [A, B]
 at [Source: REDACTED ('StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION' disabled); line: 1, column: 1]
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:2013)
	at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:1299)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._deserializeAltString(EnumDeserializer.java:450)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer._fromString(EnumDeserializer.java:307)
	at com.fasterxml.jackson.databind.deser.std.EnumDeserializer.deserialize(EnumDeserializer.java:272)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:342)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4971)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3887)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3855)
	at com.tutorialspoint.JacksonTester.main(JacksonTester.java:13)

Example - Deserialization with @JsonEnumDefaultValue

JacksonTester.java

package com.tutorialspoint;

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 
} 

Output

Run the JacksonTester and verify the output −

UNKNOWN

Here we can see, without using @JsonEnumDefaultValue, Jackson is unable to handle unknown enum value during deserialization. Using @JsonEnumDefaultValue we can define and set a default enum value for us.