when using Criteria API, in order to add filters to an entity referenced by the current one, I use this code:
criteria.createAlias("customer", "customer", Criteria.INNER_JOIN);
where customer is the customer entity property in the entity which the criteria was created for. problem is, I need to remove the referenced entity and leave only it's id in the class, i.e. replace
#ManyToOne
#JoinColumn(name = "ID_CUSTOMER")
private CustomerEntity customer;
by
#Column(name = "ID_CUSTOMER")
private Long customerId;
so, what change do I need to make in my criteria alias in order to keep it working? This is a filter example I have on it, along with the join above:
criteria.add(Restrictions.eq("customer.statusId", statusId));
Related
I have an entity with #OneToOne mapped subentity:
#Entity #Table
public class BaseEntity {
#Id
private String key;
#OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private InnerEntity inner;
}
#Entity #Table
public class InnerEntity {
private String data;
}
It was working perfectly on persist and merge operations until I decided to fetch all records in a named query (SELECT e FROM BaseEntity e). Problems are that after calling it, Hibernate fetches all records from BaseEntity and then executes distinct queries for each InnerEntity. Because table is quite big it takes much time and takes much memory.
First, I started to investigate if getInner() is called anywhere in running code. Then I tried to change fetchType to EAGER to check if Hibernate it's going to fetch it all with one query. It didn't. Another try was to change mapping to #ManyToOne. Doing this I've added updatable/insertable=false to #JoinColumn annotation. Fetching started to work perfectly - one SELECT without any JOIN (I changed EAGER back to LAZY), but problems with updating begun. Hibernate expects InnerEntity to be persisted first, but there's no property with primary key. Of course I can do this and explicity persist InnerEntity calling setKey() first, but I would rather solve this without this.
Any ideas?
If you want inner field to be loaded on demand and your relation is #OnToOneyou can try this
#OneToOne(fetch = FetchType.LAZY, optional = false)
When using HQL hibernate doesn't consider the annotations, so you should tell it how to work.
In your case you should right the HQL like this:
SELECT e FROM BaseEntity as e left join fetch e.inner
I'm using JPA 2.1 and Hibernate 4.3.7
I tried to tuned my app so I turn relationships to lazy and fetch only what I need them
I have a problem with the many-to-one relationships, when turn to lazy when I load the entity again Hibernate replace the entity by a proxy even if I fetch the entity and this proxy is not working in the view part (JSF) of the application.
The problem disapear when the many-to-one is in eager mode but hibernate perform one select more for each many-to-one even if I don't need them
#Entity
public class Department {
#Id
private Integer id;
//...
}
1/
#Entity
public class Employee {
#Id
private Integer id;
#ManyToOne(fetch = FetchType.LAZY, optional = true)
#JoinColumn(name = "id_department", referencedColumnName = "id")
private Department department;
//...
}
the JPQL query:
SELECT e FROM Employee e LEFT JOIN FETCH e.department WHERE e.id=:id
=> one select query => faster but department is of type Department_$$_jvst3ac_5f (employee.getDepartment().getClass().getCanonicalName()) and this proxy doesn't work in the view part of the application
2/
#Entity
public class Employee {
#Id
private Integer id;
#ManyToOne(fetch = FetchType.EAGER, optional = true)
#JoinColumn(name = "id_department", referencedColumnName = "id")
private Department department;
//...
}
the JPQL query:
SELECT e FROM Employee e WHERE e.id=:id
=> two selects => slower but department is loaded as Department and everything goes fine in the view part of the application
The relation is unidirectional, Department have no references of emplyees
Is this possible to have the department without proxy when using FETCH JOIN?
After the response of Luiggi I will precised that the data are fetched with lazy many-to-one + fetch join. When I do a employee.getDepartment().toString() I have Department{ id=11, ...} but the class of this department is still Department_$$_jvst3ac_5f. For reason I don't know, the JSF/PrimeFaces selectOneMenu component don't work properly whith HibernateProxy even if the data are fetched
I tried to use the Hibernate annotation #LazyToOne(LazyToOneOption.FALSE) in addition of #ManyToOne(fetch = FetchType.LAZY) but the result is similar of #ManyToOne(fetch = FetchType.EAGER) alone...
The problem is that when you use lazy loading you will obtain a proxy of the class (as you already stated) and this proxy can fetch the data from database only if the hibernatesession is still open. Seems like your session is being closed when returning the data to the view, so when trying to use the lazily-loaded field in the view you're getting the exception.
Possible solutions:
Keep the field as fetch eager and pay the overhead for each query against your entity (probably this isn't good and can affect performance, but is a solution).
Maintain your field as lazy and use the proper get method before the Hibernate session is closed in order to the proxy to retrieve the relevant data to be used after the session is closed.
My Entity is like
#Entity
#Table(name = "Item")
public class Item implements Serializable {
#Id
#GeneratedValue
#Column(name = "ID")
private long id;
#JoinColumn(name = "PARENT_ID")
#JsonIgnore
private Item parent;
}
I am doing 3 things in a single transaction
Persist some items using EntityManager
hibernate query "from item where id in newIdList"
hibernate query "from item where parent=parentid"
In First step after persisting new items I do entityManager.flush(); and flush mode here is commit.
In second step I do given hibernate query. Here I get the proper result but in third step when I do hibernate query it returns me the results. But this result does not contain the newly persisted query.
I think the problem is due to parentId condition. As per requirements I cannot change the condition. Is there any way we can solve this problem?
#JoinColumn does not establish a relationship from Item > Parent.
You need to annotate this relationship with the relevant association mapping, #OneToOne, #ManyToMany, #OneToMany, #ManyToOne etc.
Try 3rd step after commit... This is not direct solution to your problem but just give a try..
I have following Associated classes with one to one mapping.
#Entity
public class EmployeeEntity
{
#Id
private String id;
private String name;
#OneToOne(mappedBy = "employeeEntity", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
#Fetch(FetchMode.SELECT)
#JoinColumn(name = "empid")
private AddressEntity addressEntity;
...
...
getters & setters
}
#Entity
public class AddressEntity
{
#Id
#Column(unique=true, nullable=false)
#GeneratedValue(generator="gen")
#GenericGenerator(name="gen", strategy="foreign", parameters=#Parameter(name="property", value="employeeEntity"))
private String empId;
#OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
#PrimaryKeyJoinColumn
private EmployeeEntity employeeEntity;
...
getters & setters
}
I am using postgres and having tables (employeeentity, addressentity) with following foriegn key constraint on addressentity table:
Foreign-key constraints:
"fkakhilesh" FOREIGN KEY (empid) REFERENCES employeeentity(id) ON DELETE CASCADE
I have following requirements with different REST calls:
POST Rest call - should create an employee with address.
POST Rest call - should create an employee without address.
GET Rest call - should retrieve an employeee. Address should also come if it exist.
PUT Rest call - should update an employee and address (if address exists).
PUT Rest call - should update an employee and address (when address is passed and it already exists in addressentity table for empid)
PUT Rest call - should update an employee and create the address (when address is passed and it does not exists in addressentity table for empid)
I am able to perform operations 1 to 5 without any issues.
The main problem is in 6 and following questions come to my mind:
1. when i do "getSession().update(object)" , I get hibernate's StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1.
is this not possible with "update" if address does not exists? can't I create a new address during update?
do i need to change my ServiceImpl call to "getSession().merge(object) ? is this case can only be handled by calling "merge" ? how it impacts performance?
If i do merge, i get hibernate's IdentifierGenerationException: attempted to assign id from null one-to-one property.
Am i missing something here?
this can be solved by changing hibernate mapping? or somethin related to cascade.
what is the importance of #GeneratedValue(generator="gen") here? why is #parameter used in #GenericGenerator
I am new to hibernate and trying to get into the depth of hibernate mapping.
Also, I would be delighted if you could suggest me on the design as what should be the best way to handle this.
I got the fix for this. This one-one mapping is somewhat tricky and not simple as i thought initially.
I have used bidirectional one to one mapping, so it is important to call the setters of both EmployeeEntity and AddressEntity to set each other during update. for example:
employeeEntity.setAddressEntity(addressEntity) and addressEntity.setEmpoyeeEntity(empoyeeEntity) has to explicitly called.
setting alone employeeEntity.setAddressEntity(addressEntity) will not work.
Always use integer Id and use .getSession.saveOrUpdate(entity); for save or update.
In the One to One Mapping you should mention constrained=true on the child. It makes Child Id the same as Parent Id.
Use these lines for child id. I don't know Java attributes syntax.
<generator class="foreign">
<param name="property">employeeEntity</param>
</generator>
Also remove Fetch type and Cascade.All from child. I think the default fetch mode is Select which is fine. Cascade is usally used for the Parent part which is responsible for the parent-child relation.
I am trying to retrieve entities using eclipselink JPA and am looking for a way to reduce the number of queries run to retrieve a single entity. I believe I should be using the #JoinFetch annotation to retrieve sub-entities in the same query as the main entity. This works fine for a single level of join, but not for multiple levels.
In the example below, EntityA contains a collection of EntityB which contains an EntityC. When I retrieve EntityA, I want a single query to return all 3 sets of entity data. In reality it generates 2 queries, 1 joining EntityA and EntityB and then a separate query joining EntityB and EntityC.
Is it possible to combine this into one query?
class EntityA {
#OneToMany(mappedBy = "entityALink", fetch = FetchType.EAGER)
#JoinFetch
private Collection<EntityB> entityBs;
}
class EntityB {
#JoinColumn(name = "X", referencedColumnName = "Y")
#ManyToOne(optional = false, fetch = FetchType.EAGER)
private EntityA entityALink;
#JoinColumn(name = "A", referencedColumnName = "B")
#ManyToOne(optional = false, fetch = FetchType.EAGER)
#JoinFetch
private EntityC entityCLink;
}
class EntityC {
#Id
#Basic(optional = false)
#Column(name = "SomeColumn")
private String someField
}
If you need reduce number of queries, you may using lazy initialization - FetchType.LAZY instead of FetchType.EAGER - in this way jpa get data from databases when need. But you must remember, this is not working when entity is disconnected from manager. So if you send this entity to other servers in serialize the form (ex. in multi-level application) you must again connected this entity with manager. If you application runs in one server, then you don't have this problem.
Summing up is not the exact answer to your question, but maybe helpful for optimize this code.
Exact answer for you question:
You may using named queries, but then query is parse to sql native query, and you don't sure that this working as you want. But maybe you may using native query method?
em.createNativeQuery("SELECT ... your queries")
For this purpose, please read about using #SqlResultSetMapping annotation to configure result entity class...
First write a query to get EntityA.
EntityA entity = <your Query> ;
then call
Collection<EntityB> entityB = entity.getEntityBs();
for(EntityB eachB : entityB){
EntityC entityCLink = eachB.getEntityCLink();
}
Note: Create setter & getters in each entity.