Jackson - @JsonInclude之NON_ABSENT

@JsonInclude(NON_ABSENT)可用于排除空值和“不存在”的值。此处的不存在值表示引用空值的非空引用类型值（例如java.utl.concurrent.atomic.AtomicReference）。

例子

对象

@JsonInclude(JsonInclude.Include.NON_ABSENT)
public class Employee {
 	private String name;
 	private String dept;
 	private AtomicReference<String> address;
}

Main类

public class ExampleMain {
    public static void main(String[] args) throws IOException {
        Employee employee = Employee.of("Trish", null, new AtomicReference<>());
        ObjectMapper om = new ObjectMapper();
        String jsonString = om.writeValueAsString(employee);
        System.out.println(jsonString);
    }
}

{"name":"Trish"}

不加NON_ABSENT注释

如果我们根本不使用@JsonInclude，那么上面示例的输出将是：

{“ name”：“ Trish”，“ dept”：null，“ address”：null}

如果我们使用@JsonInclude（JsonInclude.Include.NON_NULL），则输出为：

{“ name”：“ Trish”，“ address”：null}