Simple question here :
If i've got an object with initialized and uninitialized values in it. Is there an easy way to find in my db all the Entities that fit this one with hibernate ? (without listing and checking every variable of the object)
Example :
I got this class :
public class User {
private int id;
private String name;
private String email;
private boolean activ;
}
I would like to be able to do that :
User user1 = new User();
user.setActive() = true;
User user2 = new User();
user.setActive(true);
user.setName("petter")
listUser1 = findAllUser(user1);
listUser2 = findAllUser(user2);
Here listUser1 will contain all the active users and listUser2 will contain all the active user that are named petter.
Thx guys !
Edit/Solution
So my here is my code (i used a class wich is similar at the one of my example).
It work just fine but the problem is that according to Eclipse : "The method createCriteria(Class) from the type SharedSessionContract is deprecated"...
public static List<Personne> findAllPersonne(Personne personne) {
List<Personne> listPersonne;
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("testhibernate0");
EntityManager entityManager = entityManagerFactory.createEntityManager();
Session session = entityManager.unwrap(Session.class);
Example personneExample = Example.create(personne);
Criteria criteria = session.createCriteria(Personne.class).add(personneExample);
listPersonne = criteria.list();
entityManager.close();
return listPersonne;
}
So .. How could i do that in a better way? I've looked into CriteriaQuery but i can't find how to use it with an example.
Yes it exists : the key word for google is "query by exemple" or "qbe".
https://dzone.com/articles/hibernate-query-example-qbe
In general, if an entity instance is already in your Persistence context, you can find it by primary key with EntityManager.find. Otherwise, you can pick up a result from your database by way of JPQL or native querying.
For your particular use case, it sounds like a querying solution would be the best fit; use one of the linked query creation methods from your entity, then use the Query.getResultList() method to pick up a list of objects that match the query criteria.
QueryByExample is also a good and valid solution, as Mr_Thorynque indicates, but as the article he linked mentions, that functionality is specific to certain JPA providers (Hibernate among them) and not JPA provider agnostic.
Related
I am using Hibernate to execute my query, in admin panel i am getting correct result but while using in Hibernate it is not giving any result.
Dao layer -
#Query("select new com.eventila.pms.entity.ReferenceLead(projectId,count(lm)) from LeadMaster lm where lm.vendorId= ?1 and lm.source = 'share' group by lm.projectId")
List<ReferenceLead> getReferenceByUser(String userId);
Pojo -
#lombok.Data
#JsonInclude(JsonInclude.Include.NON_NULL)
public class ReferenceLead {
String projectId;
Long referenceLead;
Long count;
protected ReferenceLead(){}
public ReferenceLead(String projectId,Long count) {
this.projectId=projectId;
this.count=count;
}
}
After executing this i am getting a empty list.
Please help me out.
In your select query return the fields without calling new constructor:
#Query("select projectId, count(lm) from LeadMaster lm where lm.vendorId = ?1 and lm.source = 'share' group by lm.projectId")
List<ReferenceLead> getReferenceByUser(String userId);
Hibernate will instantiate the object using these fields. Also, add #Entity annotation to your ReferenceLead class.
'source' is the keyword in SQL.
It is a keyword used in MERGE. i.e. WHEN NOT MATCHED BY SOURCE.
The word MATCHED also exhibits the same behaviour in that it gets highlighted grey in the editor.
Neither of these are reserved keywords though so if used as an identifier they do not need to be delimited (unless you find the syntax highlighting distracting).
I am trying to insert a list of rows(questions) to a table.(lets say 'Question_Table').
The whole process is performed in a single transaction. (ie. either i have to insert all questions or none). I am using Spring's declarative transaction.
I have customized the ID generation for Question_Table.(Ref : Custom id generation)
It works for the first question. But it wont work for the second question as the first row is un-committed and the table will be empty. I am not able to inject the DAO class into Id generator as it is not a spring managed bean(so i can have a method in DAO class that reads un-committed records).
What is the best approach to use in this situation.
Generator class
public class IdGenerator implements IdentifierGenerator, Configurable {
private String prefix = "";
private String queryKey = "";
#Override
public Serializable generate(SessionImplementor sessionImpl, Object arg1) throws HibernateException {
long count = (long)sessionImpl.getNamedQuery(queryKey).list().get(0);
System.out.println("COUNT >>> "+count);
long id = count + 1;
if(id == 4) throw new NullPointerException();
String generatedId = prefix + id;
return generatedId;
}
#Override
public void configure(Type arg0, Properties arg1, ServiceRegistry arg2) throws MappingException {
prefix=arg1.getProperty("PREFIX");
queryKey=arg1.getProperty("QUERY_KEY");
}
}
Query : select count(*) from Question_Table
As i stated in the comment, you maybe can use this approach if you did not have problem using combination of string and sequence. But the downside is the value will always increase even after you delete all record in that table.
If you insist of using count, then the solution is to define your entity id on save manually like. .save(question, "QSTN_"+(row_count + i)); but you will need to be able pass that row_count which i think is not a problem since it must be on one request.
I have no answer to your specific question but i'd like to share some considerations.
If your id generation depends on the database state, then it must be done at the database level (implementation is up to you, autoincrement, custom function or sequences, etc, etc)...
Otherwise if you do it at the application level you will necessary encounter concurrent access problems and have to mitigate it using some lock or dedicated transaction which will have a significant impact on the application performance and may become inconsistent later (when adding horizontal scalability or sharding for example).
However if you want to generate your ids in an applicative layer (which can be a very good idea) then you must have an unique, distributed system dedicated for this task which is not part of your current unit of work.
#Transactional(isolation = Isolation.READ_COMMITTED)
public AccountDto saveAccount(AccountDto accountDto) {
Long accountTypeId = accountDto.getAccountTypeId();
AccountTypes accountTypes = accountTypesDao.getById( accountTypeId ).orElseThrow( NotFoundAppException::new );
account.setAccountName( newAccountName );
account.setAccountType( accountTypes );
...
accountDao.save( account );
accountDao.flush();
// new inserted account id is in the transaction now
return createAccountDtoFrom( account );
}
Assume I have a model like following
class Chest {
public Id id;
public List<Drawer> drawers;
public Price price;
}
class Drawer {
public Id id;
public Price price;
}
And a JOOQ query to fetch a Chest object with its Drawers:
dsl.selectFrom(CHEST.join(DRAWERS).onKey()).where(CHEST.ID.eq(1)).fetch()
What is the best way to construct the Chest object from the result of the query above?
Thanks.
In general, using JOIN to materialise object graphs won't really work well, as you're denormalising your database entities into a table (with duplicates) before you try to normalise the data again in a mapping algorithm. JPA hides these things from you by offering an alternative query language that doesn't expose so many SQL features.
In your particular case, however, you can get this to run via the jOOQ API by using the Result.intoGroups() methods. Thus:
Map<Record, Result<Record>> result =
dsl.selectFrom(...).fetch().intoGroups(CHEST.fields());
List<Chest> list = new ArrayList<>();
for (Entry<Record, Result<Record>> entry : result.entrySet()) {
Record chest = entry.getKey();
Result<Record> drawers = entry.getValue();
list.add(new Chest(
chest.into(Id.class), // These into(Class<?>) methods assume that you
drawers.into(Drawer.class) // want to use jOOQ's DefaultRecordMapper
));
}
The above algorithm is probably incomplete, or not exactly what you need. But it'll give you a general idea of what's possible out-of-the-box via jOOQ API.
I'm trying to optmize a query that is currently taking a little longer than expected. The query returns about 11000 entities, but since they are a bit complicated and have nested entities it's somewhat slow. Since I'm not going to modify the entities, I tried setting the query/session to read-only, but it hasn't helped, it still takes just as long, maybe I'm doing something wrong. Below is a simplified code, sorry it's a little messy:
#Entity
#NamedQueries(value = {#NamedQuery(name = "demand.all", query = "select d from Demand d")})
public class Demand {
private Long ID;
private Division division;
private Client client;
private Product product;
private String code;
...
}
#Transactional(readOnly=true)
public List<Demand> getAll() {
SessionImpl sessionImpl = ((SessionImpl)em.getDelegate());
Session session = sessionImpl.getSessionFactory().openSession();
Transaction tx = session.beginTransaction();
try {
sessionImpl.connection().setReadOnly(true);
Query query = session.getNamedQuery("demand.all");
List<Demand> resultList = query.setReadOnly(true).setCacheable(false).setFlushMode(FlushMode.MANUAL).list();
sessionImpl.connection().setReadOnly(false);
tx.commit();
} catch(Exception e) {
resultList = null;
}
session.close();
return resultList;
}
I read that making the query read-only is not enough, so I tried setting the connection and transaction read-only too, but I'm not sure if it's necessary. Anyways, am I doing something wrong? What other way is there to optimize this query?
One way of doing this faster would be fetching the objects in a lazy way or depending on which are necessary and which are not. Like maybe you only need to show 5 columns in a table, instead of every single object in the hierarchy, so you create DTO to get them. If you need more information on one of them.. lets say the user clicks on a row, then you would bring the whole object hierarchy of it..
It may not apply in your case, but its one way of efficiently getting data.
I am kind of new to JPA and have read a bit about second level caching in JPA. And I think it should apply correctly to my scenario.
I have a table (say A) whose content will never change unless a new release is applied.
I need to query some data from the database : for that I have a JPQL working correctly and that uses a join between table A and an additional table (say B).
Since the contents of table A never change through the life of application, I could essentially mark this table A as Cacheable and reuse the content from Cache - rather than going to the database for that.
I have read about #NamedQuery that enables a one time JPQL to SQL translation for the life of the application. And it is not what I am looking for.
I want to know how should I go about using the Cacheable property for my purpose.
This is what I have done so far :
Marked tableA as cacheable -
#Entity
#Cacheable
#Table(name = "TableA")
public class Table{
#Id
#NotNull
#Column(updatable = false)
private String uuid;
#NotNull
#Size(min = 1)
private String description;
.
.
.
}
2. There is a DAO that does a find using the JPQL -
public Collection findAll(String description) {
final Cache cache = entityManager.getEntityManagerFactory().getCache();
if (cache.contains(TableA.class, "abc")) {
System.out.println("cached");
} else {
System.out.println("not cached");
}
final Query query = entityManager
.createQuery("Select distinct A from TableA A, IN(A.TableB) B where A.description = :description"); //$NON-NLS-1$
query.setParameter("description", description); //$NON-NLS-1$
return query.getResultList();
}
</code>
Can I take advantage of using Cacheable property in my scenario. If so, then could you suggest how?
Also, "not cached" gets printed always no matter what the value of string I use (from table) instead of "abc".
Appreciate your help. Thanks