How to ignore a field of JSON object using the Jackson library in Java?

The Jackson @JsonIgnore annotation can be used to ignore a certain property or field of a Java object. The property can be ignored both when reading JSON into Java objects and when writing Java objects into JSON. We can use the readValue() and writeValueAsString() methods of ObjectMapper class to read a JSON to Java Object and to write a Java object to JSON.

Syntax

@Target(value={ANNOTATION_TYPE,METHOD,CONSTRUCTOR,FIELD})
@Retention(value=RUNTIME)
public @interface JsonIgnore

Example

import java.io.*;
import com.fasterxml.jackson.annotation.*;
import com.fasterxml.jackson.databind.*;
public class JsonIgnoreTest {
   public static void main(String[] args) throws IOException {
      Customer customer = new Customer("110", "Surya Kiran", "Chennai");
      System.out.println(customer);
      ObjectMapper mapper = new ObjectMapper();
      String jsonString = mapper.writeValueAsString(customer);
      System.out.println("JSON: " + jsonString);
      System.out.println("---------");
      jsonString = "{\"id\":\"120\",\"name\":\"Devaraj\", \"address\":\"Banglore\"}";
      System.out.println("JSON: " + jsonString);
      customer = mapper.readValue(jsonString, Customer.class);
      System.out.println(customer);
   }
}
// Customer class
class Customer {
   private String id;
   private String name;
   @JsonIgnore
   private String address;
   public Customer() {
   }
   public Customer(String id, String name, String address) {
      this.id = id;
      this.name = name;
      this.address = address;
   }
   public String getId() {
      return id;
   }
   public String getName() {
      return name;
   }
   public String getAddress() {
      return address;
   }
   @Override
   public String toString() {
      return "Customer [id=" + id + ", name=" + name + ", address=" + address + "]";
   }
}

Output

Customer [id=110, name=Surya Kiran, address=Chennai]
JSON: {"id":"110","name":"Surya Kiran"}
---------
JSON: {"id":"120","name":"Devaraj", "address":"Banglore"}
Customer [id=120, name=Devaraj, address=null]

Raja

Published on 16-Oct-2019 12:04:37