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They are published weekly on Github. You can help us build THE programming-resources location - Star. In this post we will do a deep dive into Spring transaction management. Other upcoming posts will include:. When using JPA outside of a dependency injection container, transactions need to be handled programatically by the developer:. This way of managing transactions makes the scope of the transaction very clear in the code, but it has several disavantages:.
This is much more convenient and readable, and is currently the recommended way to handle transactions in Spring. The transactional annotation itself defines the scope of a single database transaction. The database transaction happens inside the scope of a persistence context. The persistence context is just a synchronizer object that tracks the state of a limited set of Java objects and makes sure that changes on those objects are eventually persisted back into the database. This is a very different notion than the one of a database transaction.
In such case the queries that run in the view layer are in separate database transactions than the one used for the business logic, but they are made via the same entity manager. This is the most common way to inject an entity manager:. Usually the concrete class used for the proxy is SharedEntityManagerInvocationHandler , this can be confirmed with the help a debugger.
Actually three separate components are needed:. The transaction manager will decide based on:. If the transaction manager decides to create a new transaction, then it will:. Any parts of the program that need the current entity manager or connection can retrieve them from the thread. One program component that does exactly that is the EntityManager proxy. The EntityManager proxy that we have introduced before is the last piece of the puzzle.
When the business method calls for example entityManager. Instead the business method calls the proxy, which retrieves the current entity manager from the thread, where the Transaction Manager put it. We start by defining the entity manager factory. The Spring declarative transaction management mechanism is very powerful, but it can be misused or wrongly configured easily. Understanding how it works internally is helpful when troubleshooting situations when the mechanism is not at all working or is working in an unexpected way.
The most important thing to bear in mind is that there are really two concepts to take into account: A future post will go over the most frequent pitfalls of the transactional annotation and how to avoid them.
New codingmarks added in the 12th week of Fork me on GitHub. How does Spring Transactional Really Work? You can help us build THE programming-resources location - Star In this post we will do a deep dive into Spring transaction management. Other upcoming posts will include: When does an EntityManager span multiple database transactions?
What defines the EntityManager vs Transaction relation? How does PersistenceContext work? How does Transactional work then? Get more coding resources and news. New codingmarks added in the 12th week of New codingmarks added in the 12th week of New codingmarks added in the 11th week of Published on March 19, New codingmarks added in the 10th week of Published on March 12,