In Jackson, we can use @JsonInclude(JsonInclude.Include.NON_NULL) to ignore the null fields.

P.S Tested with Jackson 2.9.8

1. Jackson default include null fields

1.1 Reviews a POJO, for testing later.

public class Staff {
    private String name;
    private int age;
    private String[] position;               
    private List<String> skills;            
    private Map<String, BigDecimal> salary; 

1.2 By default, Jackson will include the null fields.

package com.mkyong;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
public class JacksonExample {
    public static void main(String[] args) {
        ObjectMapper mapper = new ObjectMapper();
        Staff staff = new Staff("mkyong", 38);
        try {
            String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(staff);
            System.out.println(json);
        } catch (IOException e) {
            e.printStackTrace();

Output

  "name" : "mkyong",
  "age" : 38,
  "position" : null,
  "skills" : null,
  "salary" : null

To ignore the null fields, put @JsonInclude on class level or field level.

2. @JsonInclude – Class Level

import com.fasterxml.jackson.annotation.JsonInclude;
											//	ignore null fields , class level
@JsonInclude(JsonInclude.Include.NON_NULL) 	//  ignore all null fields
public class Staff {
    private String name;
    private int age;
    private String[] position;              
    private List<String> skills;           
    private Map<String, BigDecimal> salary; 
	//...

Output

  "name" : "mkyong",
  "age" : 38

3. @JsonInclude – Field Level

import com.fasterxml.jackson.annotation.JsonInclude;
public class Staff {
    private String name;
    private int age;
	@JsonInclude(JsonInclude.Include.NON_NULL) //ignore null field on this property only
    private String[] position;              
	@JsonInclude(JsonInclude.Include.NON_NULL) //ignore null field on this property only
    private List<String> skills;           
    private Map<String, BigDecimal> salary;

Output

  "name" : "mkyong",
  "age" : 38,
  "salary" : null

4. ObjectMapper.setSerializationInclusion

Alternatively, we also can configure to ignore null fields globally:

package com.mkyong;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
public class JacksonExample2 {
    public static void main(String[] args) {
        ObjectMapper mapper = new ObjectMapper();
        Staff staff = new Staff("mkyong", 38);
        try {
            // ignore the null fields globally
            mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
            String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(staff);
            System.out.println(json);
        } catch (IOException e) {
            e.printStackTrace();

Output

  "name" : "mkyong",
  "age" : 38