failed to lazily initialize a collection of role

Question

Hi I have two classes like this   public class Indicator implements Serializable             OneToMany mappedBy    indicator  fetch FetchType LAZY      private List lt IndicatorAlternateLabel gt   indicatorAlternateLabels       public List lt IndicatorAlternateLabel gt  getIndicatorAlternateLabels             return indicatorAlternateLabels                 public void setIndicatorAlternateLabels List lt IndicatorAlternateLabel gt  indicatorAlternateLabels                this indicatorAlternateLabels   indicatorAlternateLabels                       public class IndicatorAlternateLabel implements Serializable         ManyToOne cascade   CascadeType REFRESH  fetch   FetchType EAGER       JoinColumn name    IndicatorID        XmlTransient     private Indicator indicator          When I use them like this    public MetricTypeDetail getMetricTypeDetail Integer metricTypeId            Criteria crit   sessionFactory getCurrentSession   createCriteria Indicator class   sub                        add Restrictions eq  number   metricTypeId                        setResultTransformer Criteria DISTINCT ROOT ENTITY  setCacheable true           crit setMaxResults 1           Indicator indicator  Indicator  crit uniqueResult            MetricTypeDetail metricTypeDetail new MetricTypeDetail indicator           List lt IndicatorAlternateLabel gt  indicatorAlternateLabels   null          indicatorAlternateLabels indicator getIndicatorAlternateLabels            metricTypeDetail setIndicatorAlternateLabels indicatorAlternateLabels           return metricTypeDetail          This code returns an exception  failed to lazily initialize a collection of role  com porism service domain Indicator indicatorAlternateLabels  no session or session was closed  Any idea  I m very new to Hibernate

User · Answer

as suggested here solving the famous LazyInitializationException is one of the following methods:

(1) Use Hibernate.initialize

Hibernate.initialize(topics.getComments());

(2) Use JOIN FETCH

You can use the JOIN FETCH syntax in your JPQL to explicitly fetch the child collection out. This is somehow like EAGER fetching.

(3) Use OpenSessionInViewFilter

LazyInitializationException often occurs in the view layer. If you use Spring framework, you can use OpenSessionInViewFilter. However, I do not suggest you to do so. It may leads to a performance issue if not used correctly.

User · Answer

It s possible that you re not fetching the Joined Set   Be sure to include the set in your HQL   public List lt Node gt  getAll         Session session   sessionFactory getCurrentSession        Query query   session createQuery  FROM Node as n LEFT JOIN FETCH n nodeValues LEFT JOIN FETCH n nodeStats        return  query list        Where your class has 2 sets like   public class Node implements Serializable     OneToMany fetch FetchType LAZY  private Set lt NodeValue gt  nodeValues    OneToMany fetch FetchType LAZY  private Set lt NodeStat gt  nodeStats

User · Answer

Lazy exceptions occur when you fetch an object typically containing a collection which is lazily loaded  and try to access that collection    You can avoid this problem by    accessing the lazy collection within a transaction   Initalizing the collection using Hibernate initialize obj   Fetch the collection in another transaction Use Fetch profiles to select lazy non-lazy fetching runtime Set fetch to non-lazy  which is generally not recommended    Further I would recommend looking at the related links to your right where this question has been answered many times before  Also see Hibernate lazy-load application design

User · Answer

Try  swich fetchType from LAZY to EAGER       OneToMany fetch FetchType EAGER  private Set lt NodeValue gt  nodeValues        But in this case your app will fetch data from DB anyway  If this query very hard - this may impact on performance  More here  https   docs oracle com javaee 6 api javax persistence FetchType html      73

[java] failed to lazily initialize a collection of role

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