Retrieving all rows of a table without HQL?

Question

I am using Hibernate 4 and would like to simply list all rows of a table. All solutions I found suggest using something like "from tablename", but I would like to avoid hardcoding tablenames in strings.

score 136 · Accepted Answer · answered Jan 31 '12 at 17:39

136

You can use

session.createCriteria(MyEntity.class).list();

for example.

answered Jan 31 '12 at 17:39

mrab

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How could I sort this? – Matthew Moisen Oct 19 '13 at 00:05
16

session.createCriteria(MyEntity.class).addOrder(Order.asc("age")).list(); – slonik Jan 10 '14 at 13:00
5

Is there any way to make this type safe? – Sep 08 '15 at 19:05
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The method createCriteria(Class) from the type SharedSessionContract is deprecated. – Maske Sep 23 '16 at 20:08
@Maske Do you know what to use now? – jamesmstone Sep 08 '17 at 09:34

score 8 · Answer 2 · answered Jan 31 '12 at 17:36

8

HQL doesn't use table names. It uses entity names. And entity names are (by default) class names. So you can use

String hql = "select a from " + TheEntity.class.getSimpleName() + " a";

But I would favor readability over type safety here, and use

String hql = "select a from TheEntity a";

You should have automated tests for your queries anyway.

answered Jan 31 '12 at 17:36

JB Nizet

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Yes, queries are tested, but your second solution would still mean that the query wouldn't be taken into account by refactoring. – Marcus Riemer Jan 31 '12 at 17:45
1

Yes, but it would be caught by a failing test. – JB Nizet Jan 31 '12 at 17:47
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I agree that in the end its important to get correct results, but as the project is currently in early stages some kind of refactoring happens every week. So properly supporting this is quite vital at the moment. – Marcus Riemer Jan 31 '12 at 17:59
Then use my first technique, or use a Criteria. – JB Nizet Jan 31 '12 at 17:59

score -2 · Answer 3 · answered May 19 '13 at 10:46

//Hibernate Class

public class CommonDAO<T> {

 Session session = null;
 Transaction transaction = null;
 private Class<T> clazz;

 public CommonDAO(){ //constructor
    session = HibernateUtil.getSessionFactory().openSession();
    transaction = session.beginTransaction();
    Type genericSuperclass = this.getClass().getGenericSuperclass();
    if (genericSuperclass instanceof ParameterizedType) {
      ParameterizedType pt = (ParameterizedType) genericSuperclass;
      Type type = pt.getActualTypeArguments()[0];
      clazz = (Class<T>) type;
    }
 }

 public T listById(Object id) {
  T object = null;
  try {
   object = (T) session.get(clazz, (Serializable) id);
  } catch (Exception e) {
   e.printStackTrace();
  }
  return object;
 }
}

//User Class

public class UserDAO extends CommonDAO<UserMaster> { // Here UserMaster is pojo

 public UserDAO() {
  super();
 }

 public static void main(String ar[]) {
  UserMaster user = new UserDAO().listById(1); // 1 is id
  System.out.println(user.getUserName());
 }
}

It is so because your session stays open. What you want to do is *open*, *query*, *close* otherwise you will run into problems with scale. — Louis, May 07 '17 at 14:16

Retrieving all rows of a table without HQL?

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