What is this spring jpa open-in-view true property in Spring Boot

Question

I saw spring jpa open-in-view true property in Spring Boot documentation for JPA configuration    Is the true default value for this property if it s not provided at all   What does this really do  I did not find any good explaining for it  Does it make you use SessionFactory instead of EntityManagerFactory  If yes  how can I tell it to allow me to use EntityManagerFactory instead    Thanks

User · Accepted Answer

This property will register an OpenEntityManagerInViewInterceptor  which registers an EntityManager to the current thread  so you will have the same EntityManager until the web request is finished  It has nothing to do with a Hibernate SessionFactory etc

User · Answer

The OSIV Anti-Pattern Instead of letting the business layer decide how it   s best to fetch all the associations that are needed by the View layer  OSIV  Open Session in View  forces the Persistence Context to stay open so that the View layer can trigger the Proxy initialization  as illustrated by the following diagram    The OpenSessionInViewFilter calls the openSession method of the underlying SessionFactory and obtains a new Session  The Session is bound to the TransactionSynchronizationManager  The OpenSessionInViewFilter calls the doFilter of the javax servlet FilterChain object reference and the request is further processed The DispatcherServlet is called  and it routes the HTTP request to the underlying PostController  The PostController calls the PostService to get a list of Post entities  The PostService opens a new transaction  and the HibernateTransactionManager reuses the same Session that was opened by the OpenSessionInViewFilter  The PostDAO fetches the list of Post entities without initializing any lazy association  The PostService commits the underlying transaction  but the Session is not closed because it was opened externally  The DispatcherServlet starts rendering the UI  which  in turn  navigates the lazy associations and triggers their initialization  The OpenSessionInViewFilter can close the Session  and the underlying database connection is released as well   At first glance  this might not look like a terrible thing to do  but  once you view it from a database perspective  a series of flaws start to become more obvious  The service layer opens and closes a database transaction  but afterward  there is no explicit transaction going on  For this reason  every additional statement issued from the UI rendering phase is executed in auto-commit mode  Auto-commit puts pressure on the database server because each transaction issues a commit at end  which can trigger a transaction log flush to disk  One optimization would be to mark the Connection as read-only which would allow the database server to avoid writing to the transaction log  There is no separation of concerns anymore because statements are generated both by the service layer and by the UI rendering process  Writing integration tests that assert the number of statements being generated requires going through all layers  web  service  DAO  while having the application deployed on a web container  Even when using an in-memory database  e g  HSQLDB  and a lightweight webserver  e g  Jetty   these integration tests are going to be slower to execute than if layers were separated and the back-end integration tests used the database  while the front-end integration tests were mocking the service layer altogether  The UI layer is limited to navigating associations which can  in turn  trigger N 1 query problems  Although Hibernate offers  BatchSize for fetching associations in batches  and FetchMode SUBSELECT to cope with this scenario  the annotations are affecting the default fetch plan  so they get applied to every business use case  For this reason  a data access layer query is much more suitable because it can be tailored to the current use case data fetch requirements  Last but not least  the database connection is held throughout the UI rendering phase which increases connection lease time and limits the overall transaction throughput due to congestion on the database connection pool  The more the connection is held  the more other concurrent requests are going to wait to get a connection from the pool  Spring Boot and OSIV Unfortunately  OSIV  Open Session in View  is enabled by default in Spring Boot  and OSIV is really a bad idea from a performance and scalability perspective  So  make sure that in the application properties configuration file  you have the following entry  spring jpa open-in-view false  This will disable OSIV so that you can handle the LazyInitializationException the right way  Starting with version 2 0  Spring Boot issues a warning when OSIV is enabled by default  so you can discover this problem long before it affects a production system

[java] What is this spring.jpa.open-in-view=true property in Spring Boot?

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