map incomplete fields to class in hibernate
Sometimes you just want to partially use columns or fields in HQL but still want to map them into a class by Hibernate.
Well I also encounter this situation.
I have a entity class Word which has 5 fields:
@Entity(name = "word")
public class Word
{
@Id
@Basic(optional = false)
@Column(nullable = false)
private String word;
@Column(length = 10)
private String pinyin;
@Column(length = 5)
private String initial;
@Column(length = 5)
private String vowel;
@Column
private int count;
//...But my Criteria method only has two:
public List groupByInitial()
{
Criteria criteria = super.createCriteria();
criteria.setProjection(Projections.projectionList()
.add(Projections.sum("count").as("count"))
.add(Projections.groupProperty("initial").as("initial"))
);
criteria.add(Restrictions.neOrIsNotNull("pinyin", ""));
return criteria.list();
}You will surely get a Exception:
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to rugal.entity.Word
To solve this we need a transform class, namely:
public class StatsWord
{
private long count;
private String initial;
//...This could just be a POJO, with the number and same alias in you Criteria method.
Then we need to register it in Criteria method, say:
criteria.setResultTransformer(Transformers.aliasToBean(StatsWord.class));Now have a try if this is workable or not!