CODEWITHSUNDEEP
javahibernate
MemoryLeak
MemoryLeak

Reputation: 7318

can hibernate hsql automatically map the query result to a class?

I wrote a hsql: 

String queryString = "select t1.a, t1.b, t2.c from table1 t1, table2 t2 where t1.id = t2.id";

and then I have a class:

class test{
String a;
String b;
String c
 ....//other getter and setter
}

I tried: List = getHibernateTemplate().find(queryString); this doesn't work, when I use test object in jsp page, it will throw out exception.

I have to manually create a test object:

List<Object[]> list =  getHibernateTemplate().find(queryString);
test.seta(list.get(0)[0]);

is it possible for hibernate to automatically map the class for me in hsql ?

Upvotes: 0

Views: 3111

Answers (3)

Rigel Bezerra de Melo
Rigel Bezerra de Melo

Reputation: 111

The Problem is that you do not write a HQL query. You just write a normal SQL query. In HQL, because the hibernate make the mapping from table to class, you cannot make a projection. So, if you write something like

String query = "FROM Class1 WHERE ome_condition;

without the SELECT clause, the Hibernate will be able to convert the result in the proper object.

You can see more about this here: http://docs.jboss.org/hibernate/core/3.3/reference/en/html/queryhql.html

If you dont have a mapping, you may create a auxiliary class for this. Say ResultClass. Then you add @NamedNativeQuery and @SqlResultSetMapping annotations to the class:

@NamedNativeQuery(name="queryHehehe", query="select t1.field1 f1, t2.field2 f2 from table1 t1, table2 t2", resultSetMapping="mappingHehehe")
@SqlResultSetMapping(name="mappingHehehe", entities={
    @EntityResult(entityClass=my.clazz.AuxiliaryClass.class, fields = {
        @FieldResult(name="id", column="f1"),
        @FieldResult(name="other_property", column="f2")
    }),
})
public class AuxiliaryClass {
    public Long id;
    public String other_property;
}

I have never used this, but can work. Good luck.

Upvotes: 1

Don Roby
Don Roby

Reputation: 41127

If you need a query to return values from multiple tables and create an object of an unmapped class, then you need to either do what you're doing here, or use a ResultTransformer.

In order to do this with HibernateTemplate, you'll need to change the way you use the template, possibly using execute(HibernateCallback action), as you'll need to convert the sql query to a Criteria as described in Hibernate Reference Native SQL Chapter.

If you do want to try this, you'll probably want to use an AliasToBeanResultTransformer or AliasToBeanConstructorResultTransformer rather than writing your own transformer.

Upvotes: 0

Mechkov
Mechkov

Reputation: 4324

If you have a mapping for both table1 and table2 (see Prashant question above) you can do something like:

String queryString = "select t1 from table1 t1
                      inner join t1.table2 t2";

After you run the query you should have a list of t1 objects.

for(Table1 t1:listOfTable1Objects) {
   t1.getA(); //for example or whatever you want to do with your object.

}

Upvotes: 1

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