How to retrieving data from database using hibernate?

Question

When I'm using this I'm getting java.lang.ClassCastException:
java.lang.String cannot be cast to com.transgenomic.domain.Note error showing

public List<Note> getNoteDescription(Long userId) {
    Session session=sessionFactory.openSession();
    Transaction transaction=session.beginTransaction();
    SQLQuery query=session.createSQLQuery("SELECT n.description"
         + " FROM notes n, users u, tasks t "
         + " where u.userId=t.assignTo AND t.taskId=n.taskId");

    List<Note> notes=query.list();
    System.out.println("***********"+notes);
    transaction.commit();
    session.close();
    return notes;
}

It is easy with Hibernate Criteria.If you post your mapping we can help you easyly — Afsun Khammadli
– Afsun Khammadli, Commented May 22, 2015 at 9:12

Kyaw Bo · Accepted Answer · 2015-05-22 09:32:50Z

1

Hibernate returns a raw List from the Query.list method.

You are doing an unsafe cast from List<?> to List<Note> - this cannot be avoided.

The only way to make the error go away is:

List<Note> list = new LinkedList<>();
for(Note n : query.list()) {
    list.add((Note));
}

answered May 22, 2015 at 9:32

Kyaw Bo

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Comments

RichN · Accepted Answer · 2015-05-22 08:56:52Z

0

Either:
Change your select from SELECT n.description into SELECT n
or
change your method return type and type of notes from List<Note> into List<String>

Assuming type of "description" is String, using SELECT n.description will return that field only, hence query.list() will return List, this doesn't match the expected List<Note>

Using SELECT n means returning the whole object

edited May 22, 2015 at 8:56

answered May 22, 2015 at 8:50

RichN

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