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Sunday, 13 January 2013

Applying Restrictions - continued

In the last post we saw restrictions associated with equality and comparison.We can even use a single criterion instance to apply multiple equality conditions.
public static void testAllEq() {
    Map<String, Object> eqValuesMap = new HashMap<String, Object>();
    eqValuesMap.put("name", "entity2");
    eqValuesMap.put("id", 3);
        
    final Session session = sessionFactory.openSession();
    Criteria criteria = session.createCriteria(Entity.class);
    criteria.add(Restrictions.allEq(eqValuesMap));
    Entity entity = (Entity) criteria.uniqueResult(); 
    System.out.println(entity);
}
The result is :
Hibernate: 
    /* criteria query */ 
    select
        this_.ID as ID0_0_,
        this_.NAME as NAME0_0_,
        this_.DATE as DATE0_0_,
        this_.MASTER_ID as MASTER4_0_0_ 
    from
        ENTITY this_ 
    where
        (
            this_.ID=? 
            and this_.NAME=?
        )
[Entity] : ( id 3 , data : entity2 , master.Id : 1 , date : null )]
If we only need to fetch an object on the basis of id:
public static void testIdEq() {
    final Session session = sessionFactory.openSession();
    Criteria criteria = session.createCriteria(Entity.class);
    criteria.add(Restrictions.idEq(2));
    Entity entity = (Entity) criteria.uniqueResult();
    System.out.println(entity);
}
The resultant query is :
Hibernate: 
    /* criteria query */ 
    select
        this_.ID as ID0_0_,
        this_.NAME as NAME0_0_,
        this_.DATE as DATE0_0_,
        this_.MASTER_ID as MASTER4_0_0_ 
    from
        ENTITY this_ 
    where
        this_.ID = ?
[Entity] : ( id 2 , data : entity1 , master.Id : 1 , date : null )]
To apply a between condition in criteria we have the BetweenExpression:
public static void testBetween() {
    final Session session = sessionFactory.openSession();
    Criteria criteria = session.createCriteria(Entity.class);
    criteria.add(Restrictions.between("id", 2, 5));
    List<Entity> entities = criteria.list(); 
    System.out.println(entities);
}
The sql generated is:
    select
        this_.ID as ID0_0_, 
        this_.NAME as NAME0_0_,
        this_.DATE as DATE0_0_,
        this_.MASTER_ID as MASTER4_0_0_ 
    from
        ENTITY this_ 
    where
        this_.ID between ? and ?
Similarly to apply an in condition we have the InExpression.
public static void testIn() {
    final Session session = sessionFactory.openSession();
    Criteria criteria = session.createCriteria(Entity.class);
    criteria.add(Restrictions.in("id", new Integer[]{2,3,4}));
    List<Entity> entities = criteria.list(); 
    System.out.println(entities);
}
The sql generated is :
select
        this_.ID as ID0_0_,
        this_.NAME as NAME0_0_,
        this_.DATE as DATE0_0_,
        this_.MASTER_ID as MASTER4_0_0_ 
    from
        ENTITY this_ 
    where
        this_.ID in (
            ?, ?, ?
        )
The method can work with an array as well as a collection. For collections we have the EmptyExpression criterion.
public static void testEmptyCollection() {
    final Session session = sessionFactory.openSession();
    Criteria criteria = session.createCriteria(Entity.class);
    criteria.add(Restrictions.isEmpty("children"));
    List<Entity> entities = criteria.list(); 
    System.out.println(entities);
}
The resultant output is:
Hibernate: 
    /* criteria query */ 
    select
        this_.ID as ID0_0_,
        this_.NAME as NAME0_0_,
        this_.DATE as DATE0_0_,
        this_.MASTER_ID as MASTER4_0_0_ 
    from
        ENTITY this_ 
    where
        not exists (
            select
                1 
            from
                CHILD_ENTITY 
            where
                this_.ID=ENTITY_ID
        )
[]
Similarly for a not empty condition we have NotEmptyExpression. To check the collection size we have the SizeExpression.
public static void testCollectionSize() {
    final Session session = sessionFactory.openSession();
    Criteria criteria = session.createCriteria(Entity.class);
    criteria.add(Restrictions.sizeGe("children", 2));
    List<Entity> entities = criteria.list(); 
    System.out.println(entities);
}
The result is:
Hibernate: 
    /* criteria query */ 
    select
        this_.ID as ID0_0_,
        this_.NAME as NAME0_0_,
        this_.DATE as DATE0_0_,
        this_.MASTER_ID as MASTER4_0_0_ 
    from
        ENTITY this_ 
    where
        ? <= (
            select
                count(*) 
            from
                CHILD_ENTITY 
            where
                this_.ID=ENTITY_ID
        )
[[Entity] : ( id 2 , data : entity1 , master.Id : 1 , date : null )]]
The size can also be tested against not equal/less than/less than or equal/greater than and greater than or equal.

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