Jackson XML serialization drops elements of Integer type if their value is zero

[rpatrick00]

Carrying on with my little test project to isolate the issues we are seeing with Jackson, I have the following class:

@XmlRootElement(name = "employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee {
  @XmlAttribute
  @XmlID
  private String id;

  @XmlElement
  private String name;

  @XmlElement
  private EmployeeType type;

  @XmlElement
  private Integer extension;
  ...
}

And the object structure is being put together like this:

  public RunThis() {
    Company company = new Company();

    Employee employee1 = new Employee();
    employee1.setId("emp-1");
    employee1.setName("Robert Patrick");
    employee1.setType(EmployeeType.FULLTIME);
    employee1.setExtension(new Integer(32872));
    company.addEmployee(employee1);

    Employee employee2 = new Employee();
    employee2.setId("emp-2");
    employee2.setName("Michael Smith");
    employee2.setType(EmployeeType.CONTRACTOR);
    employee2.setExtension(new Integer(0));
    company.addEmployee(employee2);

    Employee employee3 = new Employee();
    employee3.setId("emp-3");
    employee3.setName("Nick D'Attoma");
    company.addEmployee(employee3);

In JAXB, the output is what you would expect:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<company>
    <employees>
        <employee id="emp-1">
            <name>Robert Patrick</name>
            <type>FULLTIME</type>
            <extension>32872</extension>
        </employee>
        <employee id="emp-2">
            <name>Michael Smith</name>
            <type>CONTRACTOR</type>
            <extension>0</extension>
        </employee>
        <employee id="emp-3">
            <name>Nick D'Attoma</name>
        </employee>
    </employees>
</company>

With Jackson, the <extension> element in missing from the emp-2 employee.

<?xml version='1.1' encoding='UTF-8'?>
<company>
  <employees>
    <employee id="emp-1">
      <name>Robert Patrick</name>
      <type>FULLTIME</type>
      <extension>32872</extension>
    </employee>
    <employee id="emp-2">
      <name>Michael Smith</name>
      <type>CONTRACTOR</type>
    </employee>
    <employee id="emp-3">
      <name>Nick D'Attoma</name>
    </employee>
  </employees>
</company>

If I set the value to anything non-zero, the element appears. How can I get Jackson to not remove Integer elements set to 0?

[rpatrick00]

Apparently, setting the following Serialization configuration causes this:

mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);

But I am not sure why you would want to define a java.lang.Integer(0) as an empty field and turning this off is not an option for us since that makes every empty element show up...

[cowtowncoder]

On inclusion criteria, this is

FasterXML/jackson-databind#952

and will be reverted for 2.7. A work-around for 2.6 would be to override serializer for java.lang.Integer.TYPE, override isEmpty().

But it sounds like there is a separate bug caused by faulty handling of exclusion in addition to that issue.

[cowtowncoder]

Actually, I think this may well be just the "too wide applicability for emptiness check", so I assume it is fixed for 2.7.

[yuvrajhshinde]

I am not geeting following header if I use Jackson approach , It is working properly with JAXB.