when to use Criteria.ALIAS_TO_ENTITY_MAP in hibernate?

Question

I am new to hibernate. i have read below line.

Criteria.ALIAS_TO_ENTITY_MAP

Please help me when to use Criteria.ALIAS_TO_ENTITY_MAP.

Thanks!

Answer 1

These are generally used with the Result Set Transformers in hibernate. Read the API or see an example. A ResultTransformer is a nice and simple interface that allows you to transform any Criteria result element.

E.g. you can make any Criteria result be returned as a java.util.Map or as a non-entity Bean.

You can read the example for the ALIAS_TO_ENTITY_MAP here. That is,

The kittens collections held by the Cat instances returned by the previous two queries are not pre-filtered by the criteria. If you want to retrieve just the kittens that match the criteria, you must use a ResultTransformer.

List cats = sess.createCriteria(Cat.class)
    .createCriteria("kittens", "kt")
        .add( Restrictions.eq("name", "F%") )
    .setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP)
    .list();
Iterator iter = cats.iterator();
while ( iter.hasNext() ) {
    Map map = (Map) iter.next();
    Cat cat = (Cat) map.get(Criteria.ROOT_ALIAS);
    Cat kitten = (Cat) map.get("kt");
}