I am learning Hibernate, and i am having problem with the join. The problem is that, the query return an List of Objects and i don't know how i must manage it
This is the code:
Query query = session.createQuery("select p.id, p.pokemon, t.types from Pokedex as p JOIN p.assPokTypes t where p.id = '001'");
List lista = query.list();
for(Object row:lista) {
System.out.println(row);
}
This is the table structure:
Pokedex (ID, pokemon)
AssPokTypes (id_pokemon, id_type, primary_type)
Thanks
Actually it returns a list of Object array not Objects
List<Object[]> lista = query.list();
for(Object[] row:lista) {
System.out.println(row[0]);//Object of the first column
System.out.println(row[1]);//Object of the second column
}
Every object from the list is column.
row[0] - p.id
row[1] - p.pokemon
....
Iterate list and use columns that you need.
Hibernate: How to get result from query with multiple classes
Related
org.hibernate
hibernate-core
4.3.8.Final
org.hibernate
hibernate-entitymanager
4.3.8.Final
My pom.xml
My Problem is: How to make a query like this...
SELECT
TABLE_D.*,
TABLE_A.NAME_A
FROM
TABLE_D
INNER JOIN
TABLE_E
ON TABLE_D.ID_TAB_E = TABLE_D.ID_TAB_D
LEFT JOIN
TABLE_C
ON TABLE_C.ID_TAB_C = TABLE_D.ID_TAB_D
INNER JOIN
TABLE_B
ON TABLE_B.ID_TAB_B = TABLE_C.ID_TAB_C
INNER JOIN
TABLE_A
ON TABLE_A.ID_TAB_A = TABLE_B.ID_TAB_B
WHERE
TABLE_A.NAME_A = "XXXX";
And Return the selected the values TABLE_D and TABLE_A in a unique Object List(ex: Object that i create to take all this fields) (I could create 1 filter, whatever...) in the JPA ? Plz Help.
If you need to return a list of selected columns in HQL you can just write your hql query and return a List of Object array, i.e.:
List<Object[]> result = session.createQuery("select a.field1, b.field2 from EntityA a join a.entityB b").list();
then you can iterate and get values, based on their type (i.e. String):
for (Object[] arr : result) {
String col1 = (String)arr[0];
String col2 = (String)arr[1];
}
I have a named parameter in JPA typed query. I am setting a list of value in condition.
I am setting a list of integer, but when JPA converts typed query to corresponding sql query it is adding a to_number function and index of the table is not used.
List<Integer> studentIds=ArrayList<Integer>
//Student id is number in database and indexed.
query = "SELECT T.* FROM STUDENT WHERE STUDENT_ID IN (:studentIds)"
TypedQuery<Object[]> typedQuery = entityManager().createQuery( query, Object[].class);
typedQuery.setParameter("studentIds", studentIds);
The issue is when JPA generates the query it is adding to_number function to convert the list
SELECT * from student t4 where student_id in (?,?,?);
filter("T4"."student_id"=TO_NUMBER(:9) OR "T4"."student_id"=TO_NUMBER(:10) OR
"T4"."student_id"=TO_NUMBER(:11) OR "T4"."PRODUCT_SET_ID"=student_id(:12)
Any thoughts how to make sure JPA does not add a to_number function, so index will be used.
I had to use an array when I was passing values into a '.in' predicate. Try this:
List<Integer> studentIds=ArrayList<Integer>
Integer[] ids = new Integer[studentIds.size()];
ids = studentIds.toArray(ids);
//Student id is number in database and indexed.
query = "SELECT T.* FROM STUDENT WHERE STUDENT_ID IN (:studentIds)"
TypedQuery<Object[]> typedQuery = entityManager().createQuery( query, Object[].class);
typedQuery.setParameter("studentIds", ids);
Say I executed a theoretical HQL query like FROM Customer. And in Customer is a getOrders() getter returning a ManyToOne collection of Order objects. This executes a SQL statement selecting from Customer with a left join to Order.
Through the object model, I can programmaticly iterate over Customers and then iterate over Orders.
However, I want to convert the hierarchical object model to a flat tabular result of the left join so that the results would look much like that of this SQL query:
SELECT *
FROM Customer
LEFT JOIN Order on Customer.customerId = Order.customerId
Sample result:
Customer.customerId ... Order.orderId Order.customerId ...
1 200 1
2 201 2
2 202 2
3 NULL NULL
Is there an easy way to do this with Hibernate?
Depends what you want at the "scalar" level which you control through using an explicitl select clause.
select c, o
from Customer c left join c.orders o
returns you List of (Customer, Order) tuples. Or:
select c.id, c.name, o.id, ...
from Customer c left join c.orders o
which returns you a scalar projection of the atomic pieces.
In both cases you get back a List. You can use "dynamic instantiation" in both cases (though really its more useful in the second case imho):
select new CustomerOrderSummary( c.id, c.name, o.id, ... )
from Customer c left join c.orders o
where CustomerOrderSummary is just a plain class with matching constructor.
Possible you can do this via expressing of result set. http://docs.jboss.org/hibernate/orm/4.0/hem/en-US/html/query_native.html
From the example:
#SqlResultSetMapping(name="GetNightAndArea", entities={
#EntityResult(name="org.hibernate.test.annotations.query.Night", fields = {
#FieldResult(name="id", column="nid"),
#FieldResult(name="duration", column="night_duration"),
#FieldResult(name="date", column="night_date"),
#FieldResult(name="area", column="area_id")
}),
#EntityResult(name="org.hibernate.test.annotations.query.Area", fields = {
#FieldResult(name="id", column="aid"),
#FieldResult(name="name", column="name")
})
})
I think you can try retrieving results in Object[] e.g. below:
EntityManager entityManager = EntityManager.getEntityManager();
Query query= entityManager.createQuery("select cust, ord from Customer cust left outer join cust.orders ord where cust.customerId = :customerId");
tradeQuery.setParameter("customerId", aCustomerId);
List<Object[]> resultList = (List<Object[]>)query.getResultList();
The retrieved resultsList will be list of Object array containing Customer and Order objects in flat.
if(!resultList.isEmpty()){
Iterator<Object[]> iter = resultList.iterator();
while(iter.hasNext()){
Object[] resultObj = (Object[])iter.next();
Customer customer= (Customer )resultObj[0];
Order order = (Order)resultObj[1];
}
}
Hope this helps!
i have next tables:
Table table1
table1Id
field1
field2
field3
Table table2
table2Id
table2_field1
table2_field2
table2_field3
table1Id
in this method i get Objects from table1 sorted by some field
public List<table1> getMost() {
DetachedCriteria criteria = (DetachedCriteria) DetachedCriteria.forClass(table1.class);
//criteria.add(Restrictions.conjunction());
criteria.addOrder(Order.desc("field1"));
List<table1> myList = (List<table1>) findByCriteria(criteria,
false, 0, 10);//get first 10 elements by some criteria
return myList;
}
then i need to get Objects from database sorted by some field, but these Objects depend on Objects from table1
public Item getTheBest(Long table1Id) {
DetachedCriteria criteria = (DetachedCriteria) DetachedCriteria
.forClass(Item.class);
DetachedCriteria maxQuery = DetachedCriteria.forClass(Item.class);
maxQuery.add(Restrictions.eq("table1Id", table1Id)).setProjection(
Projections.max("table2_field1"));
criteria.add(Restrictions.and(
Restrictions.eq("table1Id", table1Id),
Property.forName("table2_field1").eq(maxQuery)));
List<Item> result = (List<Item>) findByCriteria(criteria, false);
if (result.iterator().hasNext())
return result.iterator().next();
else
return null;
}
what i want to have is method like this:
public Item getTheBest(List<Long> table1Ids)
thus this method composes these two above methods and makes less calculations.
the idea of the method is to have a Collection of Objects, sorted by one criteria and after sorting by this criteria, we choose items by some field.
so how can i do it in hibernate?
What I understood from above is you have 'A Ordered query result and you want to filter it further".
You can do it in native SQL and use hibernate to convert query result to java objects. Following is an example
SELECT
FROM (SELECT t1.a, t1.b FROM table1 t1 {GROUP BY if needed} ORDER BY t1.a) subTable,
table2 t2
WHERE t1.a = SOMETHING
AND t2.x = SOMETHING
Can any one help me out with Criteria for following query :
SELECT * From TableA Inner Join TableB On TableA.ID=TableB.ID
I am trying with the following Criteria
Criteria criteria = session.createCriteria(TableA.class);
criteria.setFetchMode("TableB", FetchMode.JOIN);
The above criteria retrives both the table data.
Also if I need only specific columns from TableA how will the criteria Change ?
Thanks for your time.
Edit: TableA has one-to-many relationship with TableB.
Question doesn't make sense. In hibernate, the 2 Tables should actually be entities in which case they would have a relationship between them. Are you trying to randomly join 2 tables and get a result back? If so you have to use sql and use a ResultTransformer to convert the result into objects.
private ResultTransformer getResultsTransformer()
{
ResultTransformer transformer = new AliasToBeanResultTransformer(
MyResultBean.class) {
#Override
public Object transformTuple(Object[] values, String[] aliases)
{
MyResultBean row = new MyResultBean();
for (int i = 0; i < aliases.length; i++)
{
row.set(aliases[i], values[i]);
}
return (row);
}
};
return transformer;
}
Call this as follows:
Query q = session.createSQLQuery(sql);
q.setResultTransformer(getResultsTransformer());
List<MyResultBean> list = q.list();
UPDATE: If Table A has a 1-to-Many with Table B, then I find it easiest to use Alias
Criteria criteria = getSession().createCriteria(TableA.class);
criteria.createAlias("tableB","b");
criteria.add(Restrictions.eqProperty("id", "b.id");
criteria.list();
I hope this helps. Regards,
With JOIN, you need to indicate to Hibernate that you only want the "root entity", whcih is tableA. Add the following to your code:
criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);