Change Field Name in JSON using Jackson

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In this quick tutorial, I show you how to change the name of a field to map to another JSON property on serialization. Jackson library provides @JsonProperty annotation that is used to change the property name in serialized JSON.

Dependencies

Let’s first add the following dependencies to the pom.xml:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.8</version>
</dependency>

This dependency will also transitively add the following libraries to the classpath:

• jackson-annotations-2.9.8.jar
• jackson-core-2.9.8.jar
• jackson-databind-2.9.8.jar

Always use the latest versions on the Maven central repository for Jackson databind.

Change Name of Field for Serialization

1. Without using @JsonProperty Annotation

Let's first create a simple Java class and test it without adding @JsonProperty annotation.

package net.javaguides.jackson.annotations;

public class User {

    public int id;
    private String firstName;
    private String lastName;
    private String fullName;


    public User(int id, String firstName, String lastName, String fullName) {
        super();
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.fullName = fullName;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getFullName() {
        return fullName;
    }
    public void setFullName(String fullName) {
        this.fullName = fullName;
    }
}

Let's test above code with main() method:

package net.javaguides.jackson.annotations;

import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class JsonPropertyAnnotationTest {
    public static void main(String[] args) throws IOException {

        // Create ObjectMapper object.
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        User bean = new User(1, "Ramesh", "Fadatare", "Ramesh Fadatare");
        String result = mapper.writeValueAsString(bean);

        System.out.println(result);
    }
}

Output:

{
  "id" : 1,
  "firstName" : "Ramesh",
  "lastName" : "Fadatare",
  "fullName" : "Ramesh Fadatare"
}

Look at the output, if you don't use @JsonProperty annotation on class fields at all then property name will be same as a getter and setter methods of fields in the class.

2. Using @JsonProperty Annotation

Let's add a @JsonProperty annotation to User class fields to customize the output like:

{
  "id" : 1,
  "first_name" : "Ramesh",
  "last_name" : "Fadatare",
  "full_name" : "Ramesh Fadatare"
}

package net.javaguides.jackson.annotations;

import com.fasterxml.jackson.annotation.JsonProperty;

public class User {

    public int id;

    @JsonProperty("first_name")
    private String firstName;

    @JsonProperty("last_name")
    private String lastName;

    @JsonProperty("full_name")
    private String fullName;


    public User(int id, String firstName, String lastName, String fullName) {
        super();
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.fullName = fullName;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getFullName() {
        return fullName;
    }
    public void setFullName(String fullName) {
        this.fullName = fullName;
    }
}

Now, let's test above code with main() method:

package net.javaguides.jackson.annotations;

import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class JsonPropertyAnnotationTest {
    public static void main(String[] args) throws IOException {

        // Create ObjectMapper object.
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        User bean = new User(1, "Ramesh", "Fadatare", "Ramesh Fadatare");
        String result = mapper.writeValueAsString(bean);

        System.out.println(result);
    }
}

Output:

{
  "id" : 1,
  "first_name" : "Ramesh",
  "last_name" : "Fadatare",
  "full_name" : "Ramesh Fadatare"
}

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GitHub Repository

The source code of this article available on my GitHub repository at https://github.com/RameshMF/jackson-json-tutorial