How to flatten the results of a Hibernate query - java

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!

Related

Hibernate and select with join

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

How to return multiple results in a unique mapped or not object JPA

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];
}

Hibernate result list cast to get rows

Hello I had problem with iterate Hibernate ResultList
I had followed query that I got from external class:
queryContent = "select distinct c.identity, c.number, c.status, ctr.name, aab.paymentConditions.currency from AgreementStateBean ast join ast.currentAgreement aab join conagr.contract c where c.agreementStateId = ? and con.mainContractor = true ? "
And I must sum whole aab.paymentConditions.currency, check numbers of statutes and names.
I want to do this by iterate list of results:
Query q = session.createQuery(queryContent);
List result = q.list();
Long wholeCurrency, numberOfStatutes;
for(Object res : result){
//wholeCurrency += res.getColumnName?
}
My question is how to cast res Object to have possibility to get concrete column values? I had read about create map inside hibernate query but I don't know it is good practice to modyfied query string by adding
"new map(" prefix and then ")"
before from sql statement
Solution:
After All I decided to use map in my query. I modified my external query by adding hibernate map statement by replacing select by 'select new map(' and from by ') from'.
Additional thing is to add 'as' statement with name of key because without them column keys are integer.
So after all my query looks like follow:
"select new map( distinct c.identity, c.number, c.status as status, ctr.name as name, aab.paymentConditions.currency as currency ) from AgreementStateBean ast join ast.currentAgreement aab join conagr.contract c where c.agreementStateId = ? and con.mainContractor = true ? "
That was the most siutable solution for me, I tried with 'NEW com.example.MyClass' as Kostja suggested but in my case I didn't have control for incoming query so I can not rely on pernament constructor.
new List( select...
Is also interest but it also didn't tell me on with position I have my field that give me information.
If I understand correctly, you want to have a typed representation of your result without it being an entity itself. For this, you can use constructor queries:
"SELECT NEW com.example.MyClass( e.name, e.data) FROM Entity e"
MyClass has to have a matching constructor. Full qualification (com.example) is not mandatory AFAIK.
If you are using this query often, creating a view in the DB may be a good idea. You can map a view to an entity just as if it were a regular table, but please note that you cannot store changes to you data over a mapped view.
EDIT: Turns out, mapping to an unspecified Map is alright with Hibernate:
select new map( mother as mother, offspr as offspr, mate as mate )
As per http://docs.jboss.org/hibernate/orm/4.2/devguide/en-US/html/ch11.html#ql-select-clause
you can use
queryContent = "select new list(distinct c.identity, c.number, c.status, ctr.name, aab.paymentConditions.currency) from AgreementStateBean ast join ast.currentAgreement aab join conagr.contract c where c.agreementStateId = ? and con.mainContractor = true ? "
And you get List<List> as result.

hibernate criteria issue

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

JPA: Query that returns multiple entities

I'm writing a JPQL query that joins across three tables. In my resultlist I would like to get all three entities per matching row (hope that makes sense).
Any ideas?
Hibernate 3.x is my JPA provider.
IIRC, you can do a SELECT o1, o2, o3 FROM EntityA o1, EntityB o2, EntityC o3 WHERE ...., and the result will be a List<Object[3]>, where the array contents will contain the o1,o2,o3 values.
This is a Spring Data sample, however its works the same way in JPA
//HQL query
#Query("SELECT c,l,p,u FROM Course c, Lesson l, Progress p, User u "
+ "WHERE c.id=l.courseId AND l.id = p.lessonId AND p.userId = u.id AND u.id=:userId AND c.id=:courseId")
public List<Object[]> getLessonsWithProgress(#Param("userId") Integer userId, #Param("courseId")Integer courseId);
Then, I call this method and print the results:
List<Object[]> lst = courseRepository.getLessonsWithProgress(userId, courseId);
for (Object o[] : lst) {
Course c = (Course) o[0];
Lesson l = (Lesson) o[1];
Progress p = (Progress) o[2];
User u = (User) o[3];
//all the classes: Course, Lesson, Progress and User have the toString() overridden with the database ID;
System.out.printf("\nUser: %s \n Lesson: %s \n Progress: %s \n Course: %s",u,l,p,c);
}
The output #Test is here:
User: com.cassio.dao.model.User[ id=1965 ]
Lesson: com.cassio.dao.model.Lesson[ id=109 ]
Progress: com.cassio.dao.model.Progress[ id=10652 ]
Course: com.cassio.dao.model.Course[ id=30 ]
Cheers
Since You are asking JPA: Query that returns multiple entities, EclipseLink too comes under it. And I reached on this question googling for EclipseLink. So here is my solution. Hope it works for you.
TypedQuery<Object[]> query = entityManager.createQuery("select p from Post p where p.publisher.pubId= :ID order by p.createdAt desc",
Object[].class);
query.setParameter("ID", publisherID);
Then you can loop through the result objects and cast them accordingly.
for (Object result : query.getResultList()) {
myList.add((Post) result);
}
You can also try this,
Query query = entityManager.createQuery("select p from Post p where p.publisher.pubId= :ID order by p.createdAt desc");
Reference:http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying/JPQL
In case of many to one or one to many relationship how to get multiple records of one of the entities? lets say A is one entity and B is another entity but they have one to many relationship and when you get result you expect B has one record and A has more than 1 record? My query is as below but I don't know how shall I get multiple records of 2nd entity?
#Query("SELECT wl, gr FROM WatchList as wl, GeozoneReference gr " +
"WHERE wl.watchlistId = gr.objWatchList.watchlistId " +
"AND wl.watchlistId =:watchlistId")
List<Object[]> findWatchlistByWatchlistId(#Param("watchlistId") Long watchlistId);

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