Hibernate LazyInitializationException while using collection in Spring JSP page

Question

I have entities like this:

@Entity
@Table(name = \"ASSESSMENT\")
public class Assessment {

    //All other fields..

    @OneToMany(fetch = FetchType.LAZY,          


        

Answer 1

Loading AssessmentPart from EntityManager will Load Assessment @ManyToOne(fetch = FetchType.EAGER)

AssessmentPart assessmentPart = //laods a part with entity manager
Assessment assessment = assessmentPart.getAssessment();

Trying to extract AssessmentParts from assessment wont work since it's not @OneToMany(fetch = FetchType.LAZY) and session is already closed

model.put("assessmentParts", assessment.getAssessmentParts());

Get list of AssessmentParts by Assessment from EntityManager in new method should solve the problem.

Answer 2

Change

model.put("assessmentParts", assessment.getAssessmentParts());

to

Hibernate.initialize(assessment.getAssessmentParts());

to initialize your collection.

The method call assessment.getAssessmentParts() is not initializing your collection. This method call will just return you a collection wrapper and this wrapper you need to pass to the Hibernate.initialize method for manual initialization.

EDIT:

With JPA, you can fetch the AssessmentParts along with the Assessment (wherever needed) using JPQL Fetch Joins, overriding the default behavior:

SELECT a FROM Assessment asmt LEFT JOIN FETCH asmt.assessmentParts WHERE asmt.id = :id

Answer 3

In the view the entitymanager is already closed and as such the elements in your collections fail to retrieve there properties. The code you wrote in the controller doesn't initialize the elements in the collection (it is a LAZY collection) but only the collection is initialized (not the elements inside it).

Either force the entitymanager to remain open by configuring the OpenEntityManagerInViewFilter in your web configuration.

Or change your controller code to include a call to Hibernate.initialize to properly initialize your collection.

@Transactional
public void doSomething(String partId, Map<String, Object> model) {

    AssessmentPart assessmentPart = //laods a part with entity manager
    Assessment assessment = assessmentPart.getAssessment(); //Getting the assessments
    Hibernate.initialize(assesment.getAssesmentParts()); // Init collection
    model.put("assessmentParts", assessment.getAssessmentParts()); //adding all assessments parts into spring model map
}

Either that or create a custom query which forces eager fetching of the collection.