Root element missing in JSON data for DataTables

Question

I am unable to populate my dataTables due to the missing 'root' element.

Please see below code and help me how to fix it.

Piece 1:

  $('#example').DataTable({
       //"ajax": "density.txt",
       "ajax" : "getProductPropData",
       "dataType": 'json',
       "contentType": "application/json; charset=utf-8",
        "columns": [{
            "data": "densityId"
        }, {
            "data": "densityDescription"
        }, {
            data: null,
            className: "center",
            defaultContent: '<a href="#" id="edit" class="edit" data-toggle="modal" data-target="#myModal">Edit</a> / <a href="#" id="delete">Delete</a>'
                //defaultContent: '<button type="button" class="btn-default" data-toggle="modal" data-target="#myModal">Open Modal</button>'
        }]
    });

---

Piece 2: What I am doingin my Struts 2 action class.

public String execute() throws Exception {

    SessionFactory sf = (SessionFactory) ctx.getAttribute("SessionFactory");
    ProductPropertyDAO pdao = new ProductPropertyDAOImpl(sf);
    List<DensityGroup> dg = pdao.getProductPropListData("Density");

    List<DensityGroup> list = new ArrayList<DensityGroup>();
    System.out.println("SIZE is: " + dg.size());

    for (int i = 0; i < dg.size(); i++) {
        DensityGroup denpojo = new DensityGroup();
        denpojo.setDensityId(dg.get(i).getDensityId());
        denpojo.setDensityDescription(dg.get(i).getDensityDescription());
        list.add(denpojo);
    }

    data = list;

    System.out.println("JSON is :\n" + data);
    return "success";
  }

---

My JSON Data from Chrome Network tab is:

[{"densityDescription":"16 KG","densityId":"21"},
{"densityDescription":"Chitti","densityId":"22"}]

Correct data should be:

{"data" : [{"densityDescription":"16 KG","densityId":"21"},
{"densityDescription":"Chitti","densityId":"22"}]}

Edit on data variable:

private List<DensityGroup> data;

    public List<DensityGroup> getData() {
        return data;
    }

    public void setData(List<DensityGroup> data) {
        this.data = data;
    }

DensityGroup.java

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;

@Entity
@Table(name="DENGROUP")
public class DensityGroup{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    @Id
    @Column (name = "DEN_ID")
    @SequenceGenerator(name="dengroupSeq",sequenceName="density_group_seq")
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="dengroupSeq")


    private String densityId;
    public String getDensityId() {
        return densityId;
    }
    public void setDensityId(String densityId) {
        this.densityId = densityId;
    }
    public String getDensityDescription() {
        return densityDescription;
    }
    public void setDensityDescription(String densityDescription) {
        this.densityDescription = densityDescription;
    }
    @Column (name = "DEN_DESC")
    private String densityDescription;
}

Answer 1

Use ajax.dataSrc option set to empty string.

For example:

"ajax" : {
   "url": "getProductPropData",
   "dataSrc": "",
   "dataType": 'json',
   "contentType": "application/json; charset=utf-8"
}

See this example for code and demonstration.