Jackson @JsonInclude Example

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In this quick tutorial, we will discuss how to use Jackson provided @JsonInclude annotation to ignore null or empty fields in a JSON.

@JsonInclude annotation provides Include.NON_NULL attribute to ignore fields with Null values and Include.NON_EMPTY attribute to ignore fields with Empty values. 

By default, Jackson does not ignore Null and Empty fields while writing JSON. We can configure Include.NON_NULL and Include.NON_EMPTY at property level as well as at class level using @JsonInclude annotation.

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.

Table of contents

1. @JsonInclude Annotation Overview
2. Using Include.NON_NULL and Include.NON_EMPTY at the Property level
3. Using Include.NON_NULL and Include.NON_EMPTY at the Class level
4. Using Include.NON_NULL and Include.NON_EMPTY globally with ObjectMapper

1. @JsonInclude Annotation Overview

The @JsonInclude annotation contains below two values:

• Include.NON_NULL: Indicates that only properties with not null values will be included in JSON.
• Include.NON_EMPTY: Indicates that only properties that are not empty will be included in JSON.

We can configure Include.NON_NULL and Include.NON_EMPTY at property level as well as at class level using @JsonInclude annotation.

2. Using Include.NON_NULL and Include.NON_EMPTY at the Property level

package net.javaguides.jackson.annotations;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonInclude.Include;

public class Employee {

    private int id;

    @JsonInclude(Include.NON_NULL)
    private String firstName;

    @JsonInclude(Include.NON_EMPTY)
    private String lastName;

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

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

package net.javaguides.jackson.annotations;

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

public class JsonIncludeAnnotationTest {
    public static void main(String[] args) throws JsonProcessingException {

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

        Employee employee = new Employee(10, null, "");
        String result = mapper.writeValueAsString(employee);

        System.out.println(result);

    }
}

Output:

{
  "id" : 10
}

3. Using Include.NON_NULL and Include.NON_EMPTY at the Class level

Let's add @JsonInclude(Include.NON_NULL) at class level:

package net.javaguides.jackson.annotations;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonInclude.Include;

@JsonInclude(Include.NON_NULL)
public class Employee {

    private int id;

    private String firstName;

    @JsonInclude(Include.NON_EMPTY)
    private String lastName;

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

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

package net.javaguides.jackson.annotations;

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

public class JsonIncludeAnnotationTest {
    public static void main(String[] args) throws JsonProcessingException {

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

        Employee employee = new Employee(10, null, "Fadatare");
        String result = mapper.writeValueAsString(employee);

        System.out.println(result);

    }
}

Output:

{
  "id" : 10,
  "lastName" : "Fadatare"
}

4. Using Include.NON_NULL and Include.NON_EMPTY globally with ObjectMapper

Jackson also allows configuring this behavior globally on the ObjectMapper:

ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(Include.NON_NULL);
mapper.setSerializationInclusion(Include.NON_EMPTY); 

Here is the complete code:

package net.javaguides.jackson.annotations;

public class Employee {

    private int id;

    private String firstName;

    private String lastName;

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

Let's configure Include.NON_NULL and Include.NON_EMPTY globally with ObjectMapper and tested here at:

package net.javaguides.jackson.annotations;

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class JsonIncludeAnnotationTest {
    public static void main(String[] args) throws JsonProcessingException {

        // Create ObjectMapper object.
        ObjectMapper mapper = new ObjectMapper();
        mapper.setSerializationInclusion(Include.NON_NULL);
        mapper.setSerializationInclusion(Include.NON_EMPTY);

        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        Employee employee = new Employee(10, null, "");
        String result = mapper.writeValueAsString(employee);

        System.out.println(result);
    }
}

Output:

{
  "id" : 10
}

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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