java - How to ignore enum fields in Jackson JSON-to-Object mapping?

Question

I have a JSON Object something like:

{"name":"John", "grade":"A"}

or

{"name":"Mike", "grade":"B"}

or

{"name":"Simon", "grade":"C"}

etc

I am trying to map the above JSON to:

@JsonIgnoreProperties(ignoreUnknown = true)
public class Employee{
      @JsonIgnoreProperties(ignoreUnknown = true)
      public enum Grade{ A, B, C }
      Grade grade;
      String name;

  public Grade getGrade() {
    return grade;
  }

  public void setGrade(Grade grade) {
    this.grade = grade;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
}

the above mapping works fine but in the future there will be more "Grade" types let say D,E etc which breaks the existing mapping and throws the following exception

05-08 09:56:28.130: W/System.err(21309): org.codehaus.jackson.map.JsonMappingException: Can not construct instance of Employee from String value 'D': value not one of declared Enum instance names

Is there a way to ignore unknown fields with in enum types?

Thanks

Answer 1

I have found a way to do this like follows:

public static void main(String[] args) throws JsonParseException, JsonMappingException, UnsupportedEncodingException, IOException {
    String json = "{"name":"John", "grade":"D"}";

    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL, true);
    Employee employee = mapper.readValue(new ByteArrayInputStream(json.getBytes("UTF-8")), Employee.class);

    System.out.println(employee.getGrade());
}

This outputs :

null

other classes:

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class Employee {
    private String name;
    private Grade grade;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Grade getGrade() {
        return grade;
    }

    public void setGrade(Grade grade) {
        this.grade = grade;
    }
}



import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public enum Grade {A, B, C}

I haven't come across a way to do this with an annotation yet.

I hope this helps.