Jackson Annotations - @JsonAutoDetect

Overview

@JsonAutoDetect annotation is used to include properties which are not accessible otherwise.

Example - Serialization without using @JsonAutoDetect

JacksonTester.java

package com.tutorialspoint;

import java.io.IOException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonTester {
   public static void main(String args[]){
      ObjectMapper mapper = new ObjectMapper();
      try{
         Student student = new Student(1,"Mark");       
         String jsonString = mapper
            .writerWithDefaultPrettyPrinter()
            .writeValueAsString(student);
         System.out.println(jsonString);
      }
      catch (IOException e) {
         e.printStackTrace();
      }     
   }
}

class Student { 
   private int id; 
   private String name;

   Student(int id,String name) {
      this.id = id;
      this.name = name;
   }   
}

Output

Run the JacksonTester and verify the output −

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class com.tutorialspoint.Student and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77)
	at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1359)
	at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:415)
	at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:52)
	at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:29)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:503)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:342)
	at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1587)
	at com.fasterxml.jackson.databind.ObjectWriter._writeValueAndClose(ObjectWriter.java:1289)
	at com.fasterxml.jackson.databind.ObjectWriter.writeValueAsString(ObjectWriter.java:1140)
	at com.tutorialspoint.JacksonTester.main(JacksonTester.java:13)

Example - Serialization with @JsonAutoDetect

JacksonTester.java

package com.tutorialpoint;

import java.io.IOException;
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonTester {
   public static void main(String args[]){
      ObjectMapper mapper = new ObjectMapper();
      try{
         Student student = new Student(1,"Mark");       
         String jsonString = mapper
            .writerWithDefaultPrettyPrinter()
            .writeValueAsString(student);
         System.out.println(jsonString);
      }
      catch (IOException e) {
         e.printStackTrace();
      }     
   }
}
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
class Student { 
   private int id; 
   private String name;

   Student(int id,String name) {
      this.id = id;
      this.name = name;
   }   
}

Output

Run the JacksonTester and verify the output −

{
  "id" : 1,
  "name" : "Mark"
}

Here we can see, without using @JsonAutoDetect, Jackson is unable to deserialize to private fields. Using @JsonAutoDetect we can include private fields which are not accessible during deserialization otherwise.