Hi all
We’re having a few problems fetching associated entities for One-to-Many relationship in a relatively simple Criteria query:
1) We have to specify an additional join to unwanted entity in order to fetch the data we want.
2) Adding Restrictions to the query forces us to call Hibernate.initialize() on every element returned (despite using Fetch.JOIN).
Essentially, we've got Contractor and ContractorSkillGroup entities, and setFetchMode("contractorSkillGroups", FetchMode.JOIN) does not work as expected (I get LazyInitializationException). When, however, I add another join: .setFetchMode("contractorSkillGroups.skillGroup", FetchMode.JOIN), the thing starts working again. Note that the additional join is needed purely for the fetching to work, we do not need to load that data.
Here’s a representation of the schema:
Code:
------------ 1 * ---------------------- 1 * ----------
| Contractor | ----------------------| ContractorSkillGroup |--------------------| Capacity |
------------ ---------------------- ----------
| *
|
|
|
|
|
| 1
------------
| SkillGroup |
------------
Note that ContractorSkillGroup is a proper entity with its own ID and attributes, rather than purely an expression of a Many-To-Many relationship between Contractor and SkillGroup (despite the fact that its name may sound that way).
There is another interesting twist to the problem. Since we need to allow only certain values for the ContractorSkillGroup, so when we add restrictions on it (either by .createCriteria or through creating an alias) – fetching of ContractorSkillGroup entities stops working, and the only way for us to obtain them before the session is closed is to iterate through each element of the collection with Hibernate.initialize().
My question is: Is there a way for us to avoid fetching entities we don’t need and using Hibernate.initialize()? I suspect there’s some problem with our configuration that prevents things working correctly…
Many Thanks
Alex
Versions: Hibernate
3.2.3Annotations: 3.3.0
Database: Oracle 10g
JDK: 1.5
Mapping documents:Code:
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.url">jdbc:oracle:thin....</property>
<property name="connection.username">USERNAME</property>
<property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
<property name="dialect">org.hibernate.dialect.OracleDialect</property>
<property name="connection.password">PASSWORD</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.format_sql">true</property>
<!-- this will show us all sql statements -->
<property name="hibernate.show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">update</property>
<mapping class="Address"/>
<mapping class="Audit"/>
<mapping class="Capacity"/>
<mapping class="Contractor"/>
<mapping class="ContractorSkillGroup"/>
<mapping class="ContractorUser"/>
<mapping class="DwellingType"/>
<mapping class="FastTrackCapacity"/>
<mapping class="FastTrackOrder"/>
<mapping class="FileUploaded"/>
<mapping class="DispatchArea"/>
<mapping class="Order"/>
<mapping class="Platform"/>
<mapping class="ReferenceData"/>
<mapping class="ScheduledServiceOrder"/>
<mapping class="ServiceOrder"/>
<mapping class="ServiceOrderType"/>
<mapping class="SkillGroup"/>
<mapping class="SkillType"/>
<mapping class="StaffUser"/>
<mapping class="StandardCapacity"/>
<mapping class="State"/>
<mapping class="UnscheduledServiceOrder"/>
<mapping class="User"/>
<mapping class="WorkOrderType"/>
</session-factory>
</hibernate-configuration>
Code:
@SuppressWarnings("unchecked")
public void testFetch() throws Exception
{
Session session = getSession();
Criteria rootCriteria = session.createCriteria(Contractor.class)
.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY)
.setFetchMode("contractorSkillGroups", FetchMode.JOIN)
.setFetchMode("contractorSkillGroups.skillGroup", FetchMode.JOIN);
rootCriteria
.add(Restrictions.eq("id", 81L))
.add(Restrictions.eq("active", true));
// Note: I also tried using the .createCriteria (see 3 lines below) – all to the same effect.
// rootCriteria
// .createCriteria("contractorSkillGroups")
// .add(Restrictions.eq("active", true))
List<Contractor> list = rootCriteria.list();
// Note: When Restrictions on contractorSkillGroups are commented out, Hibernate.initialize() is not required
for (Contractor c : list)
{
Hibernate.initialize(c.getContractorSkillGroups());
}
session.close();
System.out.println("Results found: " + list.size());
for (Contractor contr : list)
{
System.out.println(contr);
System.out.println("\t\t" + contr.getContractorSkillGroups());
for (ContractorSkillGroup csg : contr.getContractorSkillGroups())
{
System.out.println(csg);
}
}
}
Full stack trace of any exception that occurs:The JUnit test above runs successfully, however when the line containing Hibernate.initialize() is commented out, the following exception occurrs:
Code:
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: Contractor.contractorSkillGroups, no session or session was closed
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:358)
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:350)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:343)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:86)
at org.hibernate.collection.PersistentSet.toString(PersistentSet.java:309)
at java.lang.String.valueOf(String.java:2577)
The generated SQL (show_sql=true):Code:
select
this_.id as id3_2_,
this_.OPT_LOCK as OPT2_3_2_,
this_.ACTIVE as ACTIVE3_2_,
this_.DISPATCH_FILE_LOCATION as DISPATCH4_3_2_,
this_.EMAIL_CC as EMAIL5_3_2_,
this_.EMAIL_TO as EMAIL6_3_2_,
this_.END_DATE as END7_3_2_,
this_.EXTERNAL_NRC_ID as EXTERNAL8_3_2_,
this_.EXTERNAL_SUPERVISOR_ID as EXTERNAL9_3_2_,
this_.FAST_TRACK_CAPACITY_VAR as FAST10_3_2_,
this_.NAME as NAME3_2_,
this_.START_DATE as START12_3_2_,
csg1_.id as id4_0_,
csg1_.OPT_LOCK as OPT2_4_0_,
csg1_.ACTIVE as ACTIVE4_0_,
csg1_.CONTRACTOR_ID as CONTRACTOR7_4_0_,
csg1_.DAILY_STANDARD_CAPACITY as DAILY4_4_0_,
csg1_.FAST_TRACK_ALLOWED as FAST5_4_0_,
csg1_.SKILL_GROUP_ID as SKILL6_4_0_,
skillgroup4_.id as id12_1_,
skillgroup4_.OPT_LOCK as OPT2_12_1_,
skillgroup4_.DISPATCH_AREA_ID as DISPATCH4_12_1_,
skillgroup4_.SKILL_TYPE_ID as SKILL3_12_1_
from
CONTRACTOR this_,
CONTRACTOR_SKILL_GROUP csg1_,
SKILL_GROUP skillgroup4_
where
this_.id=csg1_.CONTRACTOR_ID
and csg1_.SKILL_GROUP_ID=skillgroup4_.id(+)
and this_.id=?
and this_.ACTIVE=?
and csg1_.ACTIVE=?
Thanks again,
A.
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