@Entity
@Table(name = "DEPT_ACTIVITY")
public class DeptActivity
{
    private Long activityOid;
    private String definitionTx;
    private Boolean uosFl = false;
    private Boolean universalFl = false;
    private Boolean defaultVolumeFl = false;
    private Boolean eventVolumeFl = false;
   
    private List<Activity> activity = null;
   
    @Column(name = "ACTIVITY_OID", nullable = false)
    public Long getActivityOid()
    {
        return activityOid;
    }
    public void setActivityOid(Long activityOid)
    {
        this.activityOid = activityOid;
    }
    ...

package com.test.model.entity.dept

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EntityResult;
import javax.persistence.Id;
import javax.persistence.NamedNativeQuery;
import javax.persistence.SqlResultSetMapping;

@Entity
@SqlResultSetMapping(name = "implicit_mapping", entities = @EntityResult(entityClass = com.test.model.entity.dept.DeptActivity.class))
@NamedNativeQuery(name = "DeptActivity",
                query = "SELECT " +
                            "d.DEPT_ID as deptName, " +
                            "da.ACTIVITY_ID as activityName " +
                        "FROM " +
                            "DEPT d INNER JOIN " +
                            "DEPT_ACTIVITY da ON d.CHRONICLE_OID = da.DEPT_OID INNER JOIN " +
                        "WHERE " +
                            "(d.DEPT_OID = :deptOid) " +
                        "GROUP BY " +
                            "da.ACTIVITY_DT",
                             
                 resultSetMapping = "implicit_mapping")
public class DeptActivity
{
     private String deptName;
     private String activityName;

     @Id
     @Column
     public String getDeptName()
     {
           return deptName();
     }

     @Column
     pubic String getActivityName()
     {
           return activityName();
     }

Query query = session.getNamedQuery("DeptActivity");
query.setLong("deptOid", 56L);
List<DeptActivity> list = query.list();