可以休眠将一个pojo数据转换为几乎没有字段的另一个pojo

Question

I have two entities:

POJO 1:

@Entity
@Table(name = "tasks")
Class Task{

    @Id
    @Column(name = "id")
    private String id ;

    private String claimedId;

    private String name ; 

    private Date date;
    // gets etc...

}

and

POJO 2:

@Entity
@Table(name = "calimtask")
Class ClaimTask{

    String id ; 

    String claimedId; 

    String name; 

    // gets etc... 
} 

POJO 2 is created with some fields of POJO 1. We have data for Task table in database.

Is it possible that Hibernate can get data of id,claimedId and name using POJO 1 and could convert into the POJO 2?

Answer 1

You should never attempt to convert an Entity class from one Entity to another since each entity represents a Table.

Hibernate however provides a means to return POJO2 as an Object from the Columns selected using Hibernate Transformers class. In your case, you will need to write a custom POJO2 with getter setter of the columns you are returning. Note that is is important that the variables be named exactly like the alias columns.

public static List<ClaimTask> getDetailsfromTask(){
    Session session = HibernateUtil.getSessionFactory().openSession();
    Transaction tx = null;
    List<ClaimTask> list =  new ArrayList<ClaimTask>();
    try {
        tx = session.beginTransaction();
        Criteria cr = session.createCriteria(Task.class);
        cr.setProjection(Projections.projectionList()
                .add......;//Pick all the columns you need from Task
        cr.setResultTransformer(Transformers.aliasToBean(ClaimTask.class));
        list = (List<ClaimTask>) cr.list();
   }catch (Exception asd) {
        System.out.println(asd.getMessage());
        if (tx != null) {
            tx.rollback();
        }
    } finally {
        session.close();
    }
     return list;
}

Please note that the properties in ClaimTask should be named the same as the column aliases you pull from Task . Make sure also that ClaimTask is just plain getter setter class not an entity Class.