java - Solve Hibernate Lazy-Init issue with hibernate.enable_lazy_load_no_trans -

i have been suffering infamous hibernate exception

org.hibernate.lazyinitializationexception: not initialize proxy - no session 

now community cheering on

<property name="hibernate.enable_lazy_load_no_trans" value="true"/>

saying solves problem use caution.

what mean use caution? property does?

please give me insights. in advance.

the problem approach can have n+1 effect.

imagine have following entity:

public class person{     @onetomany // default lazy     private list<order> orderlist; } 

if have report returns 10k of persons, , if in report execute code person.getorderlist() jpa/hibernate execute 10k of queries. n+1 effect, have no control queries executed.

imagine order below:

public class order{     @onetomany // default lazy     private list<emailsent> emailsentlist; } 

imagine have iteration person.getorderlist() , every order orderyou order.getemailsentlist(). can see problem now?

for lazyinitializationexception can have solutions:

• use openinsessioninview approach. need create webfilter open , close transaction. problem n+1 effect.
• use hibernate.enable_lazy_load_no_trans configuration, hibernate , not able port project other jpa provider if needed. can have n+1 effect.
• use ejb feature named persistencecontext extended. keep context opened of several transactions. problems are: n+1 effect can happen, use lot of server memory (entities stay managed)
• use fetch in query. approach jpql/hql like: select p person p join fetch p.orderlist. query have list loaded database , not have n+1 effect. problem need write jpql each case.

if still have problem, check link: http://uaihebert.com/four-solutions-to-the-lazyinitializationexception