Jackson Ignore Null and Empty value

Today, I bump into a problem when fixing a unit test when asserting Jackson XML deserialized string.

Problem

Jackson XML deserialize null and empty value.

POJO

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@Data  //lombok
@JacksonXmlRootElement(localName = "student")
@JsonPropertyOrder({"id", "_isClassRep", "_isActive", "name", "phone"})
class Student {
    @JacksonXmlProperty(isAttribute = true, localName = "map")
    private String id;
    @JacksonXmlProperty(isAttribute = true, localName = "_isActive")
    private boolean isActive;
    @JacksonXmlProperty(isAttribute = true, localName = "_isClassRep")
    private boolean isClassRep;
    private String phone;
    private String name;
    private String address = "";
    @JacksonXmlElementWrapper(localName = "subjects")
    @JacksonXmlProperty(localName = "subject")
    private List<String> subjects = new ArrayList<>();
}

Deserialization

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public static void main(String[] args) {
        Student student = new Student();
        student.setId("id");
        student.setActive(true);
        student.setPhone("1234567890");

        XmlMapper xmlMapper = new XmlMapper();
        ByteArrayOutputStream bs = new ByteArrayOutputStream();
        xmlMapper.writerWithDefaultPrettyPrinter().writeValue(bs, student);
        String xmlString = bs.toString();
        System.out.println(xmlString);
}

Output

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<student map="id" _isClassRep="false" _isActive="true">
  <name/>
  <phone>1234567890</phone>
  <address></address>
  <subjects/>
</student>

We don’t wan Jackson to include name , address and subjects. Instead our expecting deserialized XML string would be:

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<student map="id" _isClassRep="false" _isActive="true">
  <phone>1234567890</phone>
</student>

Solution

We can tell Jackson to ignore null or empty value by using

• Include.NON_NULL - only include properties with not null value in XML.
• Include.NON_EMPTY - only include properties is not null / empty. E.g. List / Map - method isEmpty() return true ; String with length 0.

There is few way we can do.

1. Supply Include.NON_NULL or Include.NON_EMPTY at property level.

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   @Data  //lombok
   @JacksonXmlRootElement(localName = "student")
   @JsonPropertyOrder({"id", "_isClassRep", "_isActive", "name", "phone"})
   class Student {
       @JacksonXmlProperty(isAttribute = true, localName = "map")
       private String id;
       @JacksonXmlProperty(isAttribute = true, localName = "_isActive")
       private boolean isActive;
       @JacksonXmlProperty(isAttribute = true, localName = "_isClassRep")
       private boolean isClassRep;
       @JsonInclude(JsonInclude.Include.NON_NULL)    
       private String phone;
       private String name;
       @JsonInclude(JsonInclude.Include.NON_EMPTY)
       private String address = "";
       @JacksonXmlElementWrapper(localName = "subjects")
       @JacksonXmlProperty(localName = "subject")
       @JsonInclude(JsonInclude.Include.NON_EMPTY)
       private List<String> subjects = new ArrayList<>();
   }
   

   
   

2. Supply Include.NON_NULL or Include.NON_EMPTY at class level.

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   @Data  //lombok
   @JacksonXmlRootElement(localName = "student")
   @JsonPropertyOrder({"id", "_isClassRep", "_isActive", "name", "phone"})
   @JsonInclude(JsonInclude.Include.NON_EMPTY)
   class Student {
       @JacksonXmlProperty(isAttribute = true, localName = "map")
       private String id;
       @JacksonXmlProperty(isAttribute = true, localName = "_isActive")
       private boolean isActive;
       @JacksonXmlProperty(isAttribute = true, localName = "_isClassRep")
       private boolean isClassRep;
       private String phone;
       private String name;
       private String address = "";
       @JacksonXmlElementWrapper(localName = "subjects")
       @JacksonXmlProperty(localName = "subject")
       private List<String> subjects = new ArrayList<>();
   }
   

   Note: Include.NON_EMPTY at class level means any property of this class that have empty value will not be included in XML.

   
   

3. Supply Include.NON_NULL or Include.NON_EMPTY at global level with XmlMapper.

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   public static void main(String[] args) {
           Student student = new Student();
           student.setId("id");
           student.setActive(true);
           student.setPhone("1234567890");
      
           XmlMapper xmlMapper = new XmlMapper();
           xmlMapper.setSerializationInclusion(Include.NON_EMPTY); 
          
           ByteArrayOutputStream bs = new ByteArrayOutputStream();
           xmlMapper.writerWithDefaultPrettyPrinter().writeValue(bs, student);
           String xmlString = bs.toString();
           System.out.println(xmlString);
   }
   

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