title: Java POJO file null value change to default predefined value
body: <p>This is my POJO file which am using
  <code>@JsonInclude(JsonInclude.Include.NON_EMPTY)</code> for remove Null value. </p>
  
  <p>here <code>"university" : "" -</code> empty value</p>
  
  <p>current output,(jackson removed that field)</p>
  
  <pre><code>{ "id" : 1, "user_id" : 1, "education" : "s adfsdsd fsdfad", "institute" : "fsdf", "date_from" : "2014-01-01 00:00:00.0", "date_to" : "2011-03-01 00:00:00.0" }
  </code></pre>
  
  <p><strong>but i need output like</strong>(instead of null i need- not_defined)</p>
  
  <pre><code>{ "id" : 1, "user_id" : 1, "education" : "s adfsdsd fsdfad", "institute" : "fsdf", **"university" : "not_defined"**, "date_from" : "2014-01-01 00:00:00.0", "date_to" : "2011-03-01 00:00:00.0" }
  
  
  import com.fasterxml.jackson.annotation.JsonInclude;
  
  /**
   * Created by gopu on 18/3/16.
   */
  @JsonInclude(JsonInclude.Include.NON_EMPTY)
  public class UserEducation {
  
      private long id;
      private int user_id;
      private String education, institute, university, date_from, date_to;
  
      public UserEducation(long id, int user_id,  String education, String institute, String university, String date_from, String date_to) {
          this.id = id;
  </code></pre>