ClassCastException with hibernate

Question

I am trying to fetch specific fields from my entities. I need the result in my entity structure.

Following are my entities:

Country

public class CountryModel {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "CmtID")
    private int id;
    @Column(name = "CmtName")
    private String name;
    @JoinColumn(name="CmtStateID")
    @OneToMany(targetEntity=StateModel.class,fetch=FetchType.EAGER)
    private List<StateModel> state;
}

State

public class StateModel {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "SmtID")
    private int id;
    @Column(name = "SmtName")
    private String name;
}

Following is the HQL query am executing:

Query query = session.createQuery("select c.name, s.name from CountryModel c join c.state s where c.id=2");
CountryModel stateModel = (CountryModel) query.uniqueResult();

But am getting the following error:

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.muziris.entity.CountryModel

Thanks for helping.

Expected result:

Country :
        name : india
        state : 
              name : kerala
              name : goa
        name : Pak
        state :
              name : karachi

tdavid · Answer 1 · 2018-03-07T10:05:02.157

0

Since your classes are mapped you can try:

 Query query = session.createQuery("from CountryModel c where c.id=2");
 CountryModel countryModel = (CountryModel) query.uniqueResult();

Let's make use of the mapping and HQL.

From there you can use a DTO to have only the data that you need

public CountryDTO transform(CountryModel cm){
String countryName = cm.getName();
List<String> stateNames = cm.getState().stream.map(StateModel::getName)
                                              .collect(Collectors.toList());
return new CountryDTO(countryName, stateNames);
}

CountryDTO is the result that you need.

edited Mar 07 '18 at 10:05

answered Mar 07 '18 at 09:35

tdavid

95
7

no. i only need to get country name and state name. i do not need all properties – Yogesh H Shenoy Mar 07 '18 at 09:40
still it will fetch all data from DB bro. i cannot allow that to happen. – Yogesh H Shenoy Mar 07 '18 at 10:32
why not? Why would you map your classes and use HQL then? – tdavid Mar 07 '18 at 10:35
@tdavid Looks like `EAGER` loading is used. All related entities can be fetched if you will fetch entirely `CountryModel`. – v.ladynev Mar 07 '18 at 10:42
Because in projects same entity is used in different places. in all places you would not want entire data. If u do that you are giving unwanted load to DB – Yogesh H Shenoy Mar 07 '18 at 11:04

score 0 · Answer 2 · answered Mar 07 '18 at 10:38

0

Hibernate returns List<Object[]> when you use the projections. List<Object[]> is a list of specified projection columns.

Some links

https://stackoverflow.com/a/36883968/3405171

How to transform a flat result set using Hibernate

answered Mar 07 '18 at 10:38

v.ladynev

19,275
8
46
67

will it work on non sql query. I cannot use native query – Yogesh H Shenoy Mar 07 '18 at 11:05

ClassCastException with hibernate

2 Answers2