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.
Staff.java
package com.favtuts.json.nullfields;
import java.math.BigDecimal;
import java.util.List;
import java.util.Map;
public class Staff {
private String name;
private int age;
private String[] position;
private List<String> skills;
private Map<String, BigDecimal> salary;
public Staff() {
}
public Staff(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return this.age;
}
public void setAge(int age) {
this.age = age;
}
public String[] getPosition() {
return this.position;
}
public void setPosition(String[] position) {
this.position = position;
}
public List<String> getSkills() {
return this.skills;
}
public void setSkills(List<String> skills) {
this.skills = skills;
}
public Map<String,BigDecimal> getSalary() {
return this.salary;
}
public void setSalary(Map<String,BigDecimal> salary) {
this.salary = salary;
}
}
JacksonExample.java
package com.favtuts.json;
import java.io.IOException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.favtuts.json.nullfields.Staff;
public class JacksonIgnoreNullFields {
public static void main(String[] args) {
includeNullFieldsByDefault();
}
static void includeNullFieldsByDefault() {
ObjectMapper mapper = new ObjectMapper();
Staff staff = new Staff("favtuts", 38);
try {
String json = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(staff);
System.out.println(json);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
{
"name" : "favtuts",
"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
Staff.java
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" : "favtuts",
"age" : 38
}3. @JsonInclude – Field Level
Staff.java
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" : "favtuts",
"age" : 38,
"salary" : null
}4. ObjectMapper.setSerializationInclusion
Alternatively, we also can configure to ignore null fields globally:
JacksonExample2.java
package com.favtuts.json;
import java.io.IOException;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.favtuts.json.nullfields.Staff;
public class JacksonIgnoreNullFields {
public static void main(String[] args) {
ignoreNullFieldsGlobally();
}
static void ignoreNullFieldsGlobally() {
ObjectMapper mapper = new ObjectMapper();
Staff staff = new Staff("favtuts", 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" : "favtuts",
"age" : 38
}Download Source Code
$ git clone https://github.com/favtuts/java-core-tutorials-examples
$ cd java-basic/json