Jackson Annotations - @JsonIgnore

Overview

@JsonIgnore annotation is used at mark a property of special type to be ignored.

Example - Serialization without using @JsonIgnore

JacksonTester.java

package com.tutorialspoint;

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

public class JacksonTester {
   public static void main(String args[]) {
      ObjectMapper mapper = new ObjectMapper();
      try {
         Student student = new Student(1,11,"1ab","Mark");       
         String jsonString = mapper
            .writerWithDefaultPrettyPrinter()
            .writeValueAsString(student);
         System.out.println(jsonString);
      }
      catch (IOException e) { 
         e.printStackTrace();
      }   
   }
}
class Student {
   public int id;
   public String systemId;
   public int rollNo;
   public String name;

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

Output

Run the JacksonTester and verify the output −

{
  "id" : 1,
  "systemId" : "1ab",
  "rollNo" : 11,
  "name" : "Mark"
}

Example - Serialization with @JsonIgnore

JacksonTester.java

package com.tutorialspoint;

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

public class JacksonTester {
   public static void main(String args[]){
      ObjectMapper mapper = new ObjectMapper();
      try{
         Student student = new Student(1,11,"1ab","Mark");       
         String jsonString = mapper
            .writerWithDefaultPrettyPrinter()
            .writeValueAsString(student);
         System.out.println(jsonString);
      }
      catch (IOException e) { 
         e.printStackTrace();
      }     
   }
}
class Student { 
   public int id;
   @JsonIgnore
   public String systemId;
   public int rollNo;
   public String name;

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

Output

Run the JacksonTester and verify the output −

{
  "id" : 1,
  "rollNo" : 11,
  "name" : "Mark"
}

Here we can see, without using @JsonIgnore, Jackson is serializing all values by default. Using @JsonIgnore we can define the property which is to be ignored during serialization.